In article , Dave M wrote:
Don Klipstein wrote:
In article , Tony Miklos wrote:

Yes, the thread got too long. If you saw the photo, and know the
primary went open on 3 transformers, it sure looks like a problem on
the primary side. If the load was too much, those wires on the
secondary side would most likely have been at the very least
discolored from the heat.

This makes me think the most likely causes a

* Improperly connecting the transformer (such as using only 1 of
the 2 primaries of a 120/240V dual primary transformer)

* DC flowing through the secondary. That can occur if the tranny's
load has a fullwave rectifier with one diode open. If the fullwave
rectifier has discrete diodes or a dual diode, the problem may be a
bad solder joint at one of the diodes.


That's not true. an open rectifier does not allow DC current to flow
through the secondary. It's just 1/2 of the power line cycle. During the
opposite half of the cycle, no current flows in the secondary. True, it's
unidirectional current, but it's an intermittent current, not constant DC.
If your statement were true, then half-wave rectifiers wouldn't be feasible.

A unidirectional pulsing waveform has a DC component.

That analyzes to a sum of DC, fundamental frequency AC, and AC at
harmonic frequencies. The average as averaged over a whole cycle is the
DC component.

It is fairly well known that a transformer driving a halfwave rectified
load can run into core saturation problems from the DC component in the
unidirectionally pulsing current waveform.

--
- Don Klipstein )

On Tue, 12 Apr 2011 10:40:02 -0700, John Robertson
wrote:



Yes, the thread got too long. If you saw the photo, and know the
primary went open on 3 transformers, it sure looks like a problem on the
primary side. If the load was too much, those wires on the secondary
side would most likely have been at the very least discolored from the
heat.

Tony

Yes, I looked at the pictures (rather poor resolution). The failure
looks like a connection issue because there is no evidence of windings
overheating. If the output was shorted the transformer would burn up -
assuming it could sink enough current, but it would be unlikely to flare
at one spot. This is a pretty standard 115VAC transformer, I've seen
many of them...

If someone tried to pump 5000 volts into the transformer then possibly
you could get an arc like that to the transformer frame, so that would
mean a serious miss-wiring of the furnace where the igniter somehow was
connected to the primary of the transformer and then turned on.

Hard to see that happening as the transformer powers the logic board
that would enable the igniter to fire up!

John :-#)#
And the FACT that the furnace in question uses a hot plate ignitor
further removes that scenario from any semplance of possibility

On Wed, 13 Apr 2011 09:57:33 +1000, "Phil Allison"
wrote:


"Dave M"


That's not true. an open rectifier does not allow DC current to flow
through the secondary. It's just 1/2 of the power line cycle. During the
opposite half of the cycle, no current flows in the secondary.

** So the average value is non zero and that means there is a DC component
to the current.

True, it's unidirectional current, but it's an intermittent current, not
constant DC.

** It will show a nice, steady reading on a DC current meter.

The interesting thing is how there is no corresponding DC component in the
primary current.


.... Phil

Unless the half wave rectifier is on the PRIMARY side.
I don't see any evidence of that on any of the diagrams I saw, but is
there something else on this furnace circuit? By code there cannot be
- but we don't know know this to be the case - or what is on the
circuit if there is.

To the OP...
another long shot..

it looks like the primary of the transformer is wired in series with
the door safety switch. Is it possible that the door safety switch
is loose and arcing. This could cause a high voltage to appear at the
transformer and cause the insulation to fail...


Mark

Phil Allison wrote:
"Dave M"


That's not true. an open rectifier does not allow DC current to flow
through the secondary. It's just 1/2 of the power line cycle. During the
opposite half of the cycle, no current flows in the secondary.

** So the average value is non zero and that means there is a DC component
to the current.

True, it's unidirectional current, but it's an intermittent current, not
constant DC.

** It will show a nice, steady reading on a DC current meter.

The interesting thing is how there is no corresponding DC component in the
primary current.


.... Phil

Hi,
Lots of ripple. If it were on audio circuit, lots of hum!!!!

In , wrote:
On 13 Apr 2011 09:57:33 +1000, "Phil Allison" wrote:

"Dave M"

That's not true. an open rectifier does not allow DC current to flow
through the secondary. It's just 1/2 of the power line cycle. During the
opposite half of the cycle, no current flows in the secondary.

** So the average value is non zero and that means there is a DC component
to the current.

True, it's unidirectional current, but it's an intermittent current, not
constant DC.

** It will show a nice, steady reading on a DC current meter.

The interesting thing is how there is no corresponding DC component in the
primary current.

.... Phil

Unless the half wave rectifier is on the PRIMARY side.

There won't be a rectifier feeding the primary of a transformer with DC.
A transformer does not pass DC from one winding to another the way it does
with AC.

Changing AC that transformers work with to DC that electronics work with
has to occur downstream of the transformer.

I don't see any evidence of that on any of the diagrams I saw, but is
there something else on this furnace circuit? By code there cannot be
- but we don't know know this to be the case - or what is on the
circuit if there is.

I have yet to look at these diagrams, but is the circuit board
powered by this tranny shown to "board level" as opposed to "component
level"? If so, then the board can have, probably does have, a rectifier
not shown in the diagram.
--
- Don Klipstein )

On 4/12/2011 9:23 PM Don Klipstein spake thus:

I have yet to look at these diagrams, but is the circuit board
powered by this tranny shown to "board level" as opposed to "component
level"? If so, then the board can have, probably does have, a rectifier
not shown in the diagram.

With all the pontificating you've been doing here, Don, I would've
thought you'd at least had glanced at the wiring diagrams the OP posted,
way up there somewhere. Sheesh.

The controller is shown as a block. It most certainly has at least one
rectifier on it, as it contains electronics that no doubt requires DC
power to operate. Thought you'd have figured it out. (Not just a relay
board.)


--
The current state of literacy in our advanced civilization:

yo
wassup
nuttin
wan2 hang
k
where
here
k
l8tr
by

- from Usenet (what's *that*?)

On Apr 12, 8:49*pm, (Don Klipstein) wrote:
In article , Dave M wrote:
Don Klipstein wrote:
In article , Tony Miklos wrote:

Yes, the thread got too long. *If you saw the photo, and know the
primary went open on 3 transformers, it sure looks like a problem on
the primary side. *If the load was too much, those wires on the
secondary side would most likely have been at the very least
discolored from the heat.

*This makes me think the most likely causes a

* * Improperly connecting the transformer (such as using only 1 of
*the 2 primaries of a 120/240V dual primary transformer)

* * DC flowing through the secondary. *That can occur if the tranny's
*load has a fullwave rectifier with one diode open. *If the fullwave
*rectifier has discrete diodes or a dual diode, the problem may be a
*bad solder joint at one of the diodes.

That's not true. *an open rectifier does not allow DC current to flow
through the secondary. *It's just 1/2 of the power line cycle. *During the
opposite half of the cycle, no current flows in the secondary. *True, it's
unidirectional current, but it's an intermittent current, not constant DC.
If your statement were true, then half-wave rectifiers wouldn't be feasible.

* A unidirectional pulsing waveform has a DC component.

* That analyzes to a sum of DC, fundamental frequency AC, and AC at
harmonic frequencies. *The average as averaged over a whole cycle is the
DC component.

* It is fairly well known that a transformer driving a halfwave rectified
load can run into core saturation problems from the DC component in the
unidirectionally pulsing current waveform.

--
*- Don Klipstein )- Hide quoted text -

- Show quoted text -

Interesting theory. One helpful piece of info which it's quite
amazing we
still don't have is what the currents are on both sides of the
transformer.
For saturation to occur I would think the transformer would have to
be close
to fully loaded. Which it could be, given the trends to lower cost,
cheaper
components, etc.

On Wed, 13 Apr 2011 04:23:08 +0000 (UTC), (Don
Klipstein) wrote:

In , wrote:
On 13 Apr 2011 09:57:33 +1000, "Phil Allison" wrote:

"Dave M"

That's not true. an open rectifier does not allow DC current to flow
through the secondary. It's just 1/2 of the power line cycle. During the
opposite half of the cycle, no current flows in the secondary.

** So the average value is non zero and that means there is a DC component
to the current.

True, it's unidirectional current, but it's an intermittent current, not
constant DC.

** It will show a nice, steady reading on a DC current meter.

The interesting thing is how there is no corresponding DC component in the
primary current.

.... Phil

Unless the half wave rectifier is on the PRIMARY side.

There won't be a rectifier feeding the primary of a transformer with DC.
A transformer does not pass DC from one winding to another the way it does
with AC.

I fully understand that, byt what happens if, say, the Mrs plugs her
cheap blow drier into the same circuit as the primary of the
transformer is plugged in to, and she puts the blow drier on low (it
uses a half wave rectifier to drop the power to the heater) - and you
end up with a DC component on the primary - which saturates the
primary without any increase in secondary (load) current or power.

Changing AC that transformers work with to DC that electronics work with
has to occur downstream of the transformer.

I am very aware of that.
I don't see any evidence of that on any of the diagrams I saw, but is
there something else on this furnace circuit? By code there cannot be
- but we don't know know this to be the case - or what is on the
circuit if there is.

I have yet to look at these diagrams, but is the circuit board
powered by this tranny shown to "board level" as opposed to "component
level"? If so, then the board can have, probably does have, a rectifier
not shown in the diagram.

Again, fully aware that the circuit board WILL have a rectifier which
is not shown on the diagram, and better than 95% chance it is full
wave bridge rectifier. There are precious few solid state control
devices that run on AC.

On Wed, 13 Apr 2011 04:22:15 -0700 (PDT), "
wrote:

On Apr 12, 8:49Â*pm, (Don Klipstein) wrote:
In article , Dave M wrote:
Don Klipstein wrote:
In article , Tony Miklos wrote:

Yes, the thread got too long. Â*If you saw the photo, and know the
primary went open on 3 transformers, it sure looks like a problem on
the primary side. Â*If the load was too much, those wires on the
secondary side would most likely have been at the very least
discolored from the heat.

Â*This makes me think the most likely causes a

* Â* Improperly connecting the transformer (such as using only 1 of
Â*the 2 primaries of a 120/240V dual primary transformer)

* Â* DC flowing through the secondary. Â*That can occur if the tranny's
Â*load has a fullwave rectifier with one diode open. Â*If the fullwave
Â*rectifier has discrete diodes or a dual diode, the problem may be a
Â*bad solder joint at one of the diodes.

That's not true. Â*an open rectifier does not allow DC current to flow
through the secondary. Â*It's just 1/2 of the power line cycle. Â*During the
opposite half of the cycle, no current flows in the secondary. Â*True, it's
unidirectional current, but it's an intermittent current, not constant DC.
If your statement were true, then half-wave rectifiers wouldn't be feasible.

Â* A unidirectional pulsing waveform has a DC component.

Â* That analyzes to a sum of DC, fundamental frequency AC, and AC at
harmonic frequencies. Â*The average as averaged over a whole cycle is the
DC component.

Â* It is fairly well known that a transformer driving a halfwave rectified
load can run into core saturation problems from the DC component in the
unidirectionally pulsing current waveform.

--
Â*- Don Klipstein )- Hide quoted text -

- Show quoted text -

Interesting theory. One helpful piece of info which it's quite
amazing we
still don't have is what the currents are on both sides of the
transformer.
For saturation to occur I would think the transformer would have to
be close
to fully loaded. Which it could be, given the trends to lower cost,
cheaper
components, etc.


As I posted in an earlier post (not sure what values I used, but I'll
run a scenario anyway), assuming a 2 ohm winding, a 2 volt DC
component will cause 1 AMP of current to flow in the winding. IF that
coil happens to be the primary of a 40va transformer, The full load
current on that transformer is about 350ma, so the probability that 1
amp of current in the primary, with no AC voltage applied, would have
more than saturated the core is pretty good.
Add the quiescent current of the primary, and you have a saturated
core. And that's just a 2 volt DC component on a 115 volt primary.

If the primary is 4 ohms instead of 2, you have half an amp with 2
volts, or 1 amp with 4 volts.

Doesn't take much to put 2 volts DC across a 115 volt line.

See http://sound.westhost.com/articles/xfmr-dc.htm for more
information from someone who may have a bit more credibility than you
guys may give me.

So, it's cheaper to put a half wave rectifier in, instead of
a second coil of heater wire? I rather doubt that.

--
Christopher A. Young
Learn more about Jesus
www.lds.org
..


wrote in message
...

what happens if, say, the Mrs plugs her
cheap blow drier into the same circuit as the primary of the
transformer is plugged in to, and she puts the blow drier on
low (it
uses a half wave rectifier to drop the power to the
heater) - and you
end up with a DC component on the primary - which saturates
the
primary without any increase in secondary (load) current or
power.

As I posted in an earlier post (not sure what values I used, but I'll
run a scenario anyway), assuming a 2 ohm winding, a 2 volt DC
component will cause 1 AMP of current to flow in the winding. IF that
coil happens to be the primary of a 40va transformer,

** A 40VA tranny designed for 120 volt 60 Hz operation has a primary
resistance of 16 ohms.

Getting a 2 volt DC offset on a 120 volt AC supply takes some doing.

Doesn't take much to put 2 volts DC across a 115 volt line.

** Like hell.

For a 2 volt DC offset to exist, the peak voltage in one polarity must be
6.3 volts higher than the other.

With a typical impedance at the outlet of 0.25ohms, this equates to 25 amps
peak load in one polarity and none in the other.


See http://sound.westhost.com/articles/xfmr-dc.htm for more
information from someone who may have a bit more credibility than you
guys may give me.


** I helped Rod write that article.

Toroidal trannys are very sensitive to DC offsets while regular E-core types
are hardly bothered by them - the difference is that while the former has
no air gaps in the core, the latter is full of them.


..... Phil

On Wed, 13 Apr 2011 19:22:37 -0400, "Stormin Mormon"
wrote:

So, it's cheaper to put a half wave rectifier in, instead of
a second coil of heater wire? I rather doubt that.

I don't remember the details, but I know quite a few DO work that way
- and they also used 12 volt DC blower motors, without a transformer,
by basically using the heater element as a rheostat..

"Stormin Mormon"


So, it's cheaper to put a half wave rectifier in, instead of
a second coil of heater wire? I rather doubt that.

I don't remember the details, but I know quite a few DO work that way
- and they also used 12 volt DC blower motors, without a transformer,
by basically using the heater element as a rheostat..


** My 1600 watt "Black & Decker" hot air gun is made exactly like that.



..... Phil

Steve Turner wrote:
On 4/9/2011 7:29 PM, Jim Yanik wrote:
wrote in
m:

"Steve Turner" wrote in message ...

A continuation of the "Why does the 115V-24V transformer keep
blowing on my Trane XB80?" discussion I started on 04/02/2011.

Yep, My A/C unit blew another transformer. Pictures (and wiring
diagram) he

http://www.flickr.com/photos/bbqboye...7626457562742/

Trane's manual for the unit is here (for perhaps better viewing of
the wiring diagrams that I also copied to my above flickr site as
jpg images):



http://www.trane.com/webcache/un/fur...oduct/22-1666-
07_04012009.pdf

As you can probably see in the pictures, there is visible charring
of the 115V leads going into the transformer, and of course the 115V
circuit is open (again). If you didn't see my first thread, this is
the third transformer the unit has blown. In the previous
discussion, it was discussed that perhaps the first one just blew
because of old age (6 years), and the second blew because it wasn't
a proper replacement (poor quality, made in China, etc.). This
third unit is most certainly a proper replacement, and it's most
certainly indicative of a real problem I have somewhere else in the
unit. I didn't see any such charring on the previous two units, at
least not like this.

I never got a real chance to test out the system after installing
this third transformer. We had cool weather for several days, and I
never tried to force the system to come on so I could monitor it;
that was probably a mistake. Unfortunately, I was also absent from
the premises during the extended times when the unit was most likely
operational, so that didn't help either. However, my family tells me
that it WAS working and cooling the house rather nicely, for at
least a day, perhaps two. I'm getting 115V in all the right places,
so it doesn't look like an over-voltage condition to me. Perhaps
it's an overheating condition? It looks to me like the only real
load on this circuit is the blower motor; could the motor be causing
this? The blower spins freely when I turn it by hand. Start
capacitor on the motor maybe? Relay on the control board perhaps?

a bad start cap would not affect the 24v control transformer,that just
powers the controller board and relays.
either something is loading the transformer or a problem with input
voltage.


Just a thought,

When you put the new transformer in does the "Diagnostic Light" LED
turn on ?
Does the LED blink or flash in one of the patterns indicated in the
"diagnostic codes" section that you posted a link to ?

The "diagnostic codes" imply that the control board can detect
several of the problems mentioned by others.
Maybe a good starting point as there is not enough time to test with
test equipment.

robb



a line voltage monitor may be needed to see if there's some short-term
overvoltage applied to the transformer,and a oscilloscope may
determine if
the input waveform is sinusoidal or otherwise,because 60hz iron core
tranformers don't like extreme distortion on their input,it gets
converted
to heat,not output voltage. a DMM will not show line distortion or short
term overvoltages.
are the wires burned close to the transformer,or over their entire
length?

I peeled the insulation back from the hot and neutral wires and the
burning only occurred right at the terminals, no more than 1/4" into the
wiring.


Steve,

Not to be rude or anything, but a LOT of talk has gone on about your
problem and I have not seen any further posts from you on the matter. No
comments about any suggestions at all.

I'm not going to spend any more time on this thread until we hear back
from the original poster with more information otherwise we are simply
blowing smoke (sorry - couldn't resist).

John :-#)#

--
(Please post followups or tech enquiries to the newsgroup)
John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9
Call (604)872-5757 or Fax 872-2010 (Pinballs, Jukes, Video Games)
www.flippers.com
"Old pinballers never die, they just flip out."

On 4/13/2011 10:51 PM, John Robertson wrote:
Steve Turner wrote:
On 4/9/2011 7:29 PM, Jim Yanik wrote:
wrote in
m:

"Steve Turner" wrote in message ...

A continuation of the "Why does the 115V-24V transformer keep
blowing on my Trane XB80?" discussion I started on 04/02/2011.

Yep, My A/C unit blew another transformer. Pictures (and wiring
diagram) he

http://www.flickr.com/photos/bbqboye...7626457562742/

Trane's manual for the unit is here (for perhaps better viewing of
the wiring diagrams that I also copied to my above flickr site as
jpg images):



http://www.trane.com/webcache/un/fur...oduct/22-1666-
07_04012009.pdf

As you can probably see in the pictures, there is visible charring
of the 115V leads going into the transformer, and of course the 115V
circuit is open (again). If you didn't see my first thread, this is
the third transformer the unit has blown. In the previous
discussion, it was discussed that perhaps the first one just blew
because of old age (6 years), and the second blew because it wasn't
a proper replacement (poor quality, made in China, etc.). This
third unit is most certainly a proper replacement, and it's most
certainly indicative of a real problem I have somewhere else in the
unit. I didn't see any such charring on the previous two units, at
least not like this.

I never got a real chance to test out the system after installing
this third transformer. We had cool weather for several days, and I
never tried to force the system to come on so I could monitor it;
that was probably a mistake. Unfortunately, I was also absent from
the premises during the extended times when the unit was most likely
operational, so that didn't help either. However, my family tells me
that it WAS working and cooling the house rather nicely, for at
least a day, perhaps two. I'm getting 115V in all the right places,
so it doesn't look like an over-voltage condition to me. Perhaps
it's an overheating condition? It looks to me like the only real
load on this circuit is the blower motor; could the motor be causing
this? The blower spins freely when I turn it by hand. Start
capacitor on the motor maybe? Relay on the control board perhaps?

a bad start cap would not affect the 24v control transformer,that just
powers the controller board and relays.
either something is loading the transformer or a problem with input
voltage.


Just a thought,

When you put the new transformer in does the "Diagnostic Light" LED
turn on ?
Does the LED blink or flash in one of the patterns indicated in the
"diagnostic codes" section that you posted a link to ?

The "diagnostic codes" imply that the control board can detect
several of the problems mentioned by others.
Maybe a good starting point as there is not enough time to test with
test equipment.

robb



a line voltage monitor may be needed to see if there's some short-term
overvoltage applied to the transformer,and a oscilloscope may determine if
the input waveform is sinusoidal or otherwise,because 60hz iron core
tranformers don't like extreme distortion on their input,it gets converted
to heat,not output voltage. a DMM will not show line distortion or short
term overvoltages.
are the wires burned close to the transformer,or over their entire length?

I peeled the insulation back from the hot and neutral wires and the burning
only occurred right at the terminals, no more than 1/4" into the wiring.


Steve,

Not to be rude or anything, but a LOT of talk has gone on about your problem
and I have not seen any further posts from you on the matter. No comments about
any suggestions at all.

I'm not going to spend any more time on this thread until we hear back from the
original poster with more information otherwise we are simply blowing smoke
(sorry - couldn't resist).

John :-#)#

Just mentioned elsewhere that I have a new transformer on order and I can't
really do anything until that arrives. Rest assured I appreciate all the input
and I'm taking it all into consideration. Thanks.

On Wed, 13 Apr 2011 23:32:56 -0500, Steve Turner
wrote:



Just mentioned elsewhere that I have a new transformer on order and I can't
really do anything until that arrives. Rest assured I appreciate all the input
and I'm taking it all into consideration. Thanks.

You bought the fuses, right?
I DON'T want to hear about another blown transformer.

--Vic

In m, D Nebenzahl wrote:
On 4/12/2011 9:23 PM Don Klipstein spake thus:

I have yet to look at these diagrams, but is the circuit board
powered by this tranny shown to "board level" as opposed to "component
level"? If so, then the board can have, probably does have, a rectifier
not shown in the diagram.

With all the pontificating you've been doing here, Don, I would've
thought you'd at least had glanced at the wiring diagrams the OP posted,
way up there somewhere. Sheesh.

The controller is shown as a block. It most certainly has at least one
rectifier on it, as it contains electronics that no doubt requires DC
power to operate. Thought you'd have figured it out. (Not just a relay
board.)

With such indication even as described here giving low indication as
to rectification having a 1-component bridge rectifier, 4 discrete diodes,
a fed-with-center-tap 2-diode fullwave scheme, 2 separate diodes or a
single 3-lead dual-diode used for that...

If the controller is only shown as a block, how well does it show the
rectifier scheme, as in whether the rectifier's diodes are discrete
individual diodes or integrated into one rectifier package?

If anyone here sees that noted to such extent that it's not a waste of
my time to take a look there, please pipe up!
--
- Don Klipstein )

"Vic Smith"
Steve Turner

Just mentioned elsewhere that I have a new transformer on order and I
can't
really do anything until that arrives. Rest assured I appreciate all the
input
and I'm taking it all into consideration. Thanks.

You bought the fuses, right?
I DON'T want to hear about another blown transformer.


** Be real smart for the OP to purchase some OTHER 120/24 volt tranny and
use it.

The things are a dime a dozen.

And fit a "slo-blo" 1/4 amp fuse to the primary.



..... Phil

Phil Allison wrote:
"Vic Smith"
Steve Turner

Just mentioned elsewhere that I have a new transformer on order and I
can't
really do anything until that arrives. Rest assured I appreciate all the
input
and I'm taking it all into consideration. Thanks.

You bought the fuses, right?
I DON'T want to hear about another blown transformer.


** Be real smart for the OP to purchase some OTHER 120/24 volt tranny and
use it.

The things are a dime a dozen.

And fit a "slo-blo" 1/4 amp fuse to the primary.



.... Phil

Hmmm,
What is fuse gonna do? Instead of blowing x-former,, blow fuses?
Then still it is not right. Let;s go back from begining. How old
is the system? When this blowing tranny started? From day 1 or some
time(month, years after the system is installed? If tranny is hot to
touch when in use, that is rad flag.

In article ,
Steve Turner wrote:

Just mentioned elsewhere that I have a new transformer on order and I can't
really do anything until that arrives.

Sure you could. You could open up those other two transformers and check
for an open thermal fuse. As I recall, you said neither of them failed
in the same manner as the third. I still say you could have 3 distinct,
unrelated failures.

"Tony Hwang"

** Be real smart for the OP to purchase some OTHER 120/24 volt tranny
and
use it.

The things are a dime a dozen.

And fit a "slo-blo" 1/4 amp fuse to the primary.

What is fuse gonna do?


** Blow immediately if the tranny is overloaded.


Instead of blowing x-former,, blow fuses?


** This is the usual purpose of fuses.


Then still it is not right.

** Then you can find the cause of the overload - cos the tranny still
functions.

****wit.


..... Phil

Steve Turner wrote:
On 4/13/2011 10:51 PM, John Robertson wrote:
Steve Turner wrote:
On 4/9/2011 7:29 PM, Jim Yanik wrote:
wrote in
m:

"Steve Turner" wrote in message ...

A continuation of the "Why does the 115V-24V transformer keep
blowing on my Trane XB80?" discussion I started on 04/02/2011.

Yep, My A/C unit blew another transformer. Pictures (and wiring
diagram) he

http://www.flickr.com/photos/bbqboye...7626457562742/

Trane's manual for the unit is here (for perhaps better viewing of
the wiring diagrams that I also copied to my above flickr site as
jpg images):



http://www.trane.com/webcache/un/fur...oduct/22-1666-

07_04012009.pdf

As you can probably see in the pictures, there is visible charring
of the 115V leads going into the transformer, and of course the 115V
circuit is open (again). If you didn't see my first thread, this is
the third transformer the unit has blown. In the previous
discussion, it was discussed that perhaps the first one just blew
because of old age (6 years), and the second blew because it wasn't
a proper replacement (poor quality, made in China, etc.). This
third unit is most certainly a proper replacement, and it's most
certainly indicative of a real problem I have somewhere else in the
unit. I didn't see any such charring on the previous two units, at
least not like this.

I never got a real chance to test out the system after installing
this third transformer. We had cool weather for several days, and I
never tried to force the system to come on so I could monitor it;
that was probably a mistake. Unfortunately, I was also absent from
the premises during the extended times when the unit was most likely
operational, so that didn't help either. However, my family tells me
that it WAS working and cooling the house rather nicely, for at
least a day, perhaps two. I'm getting 115V in all the right places,
so it doesn't look like an over-voltage condition to me. Perhaps
it's an overheating condition? It looks to me like the only real
load on this circuit is the blower motor; could the motor be causing
this? The blower spins freely when I turn it by hand. Start
capacitor on the motor maybe? Relay on the control board perhaps?

a bad start cap would not affect the 24v control transformer,that just
powers the controller board and relays.
either something is loading the transformer or a problem with input
voltage.


Just a thought,

When you put the new transformer in does the "Diagnostic Light" LED
turn on ?
Does the LED blink or flash in one of the patterns indicated in the
"diagnostic codes" section that you posted a link to ?

The "diagnostic codes" imply that the control board can detect
several of the problems mentioned by others.
Maybe a good starting point as there is not enough time to test with
test equipment.

robb



a line voltage monitor may be needed to see if there's some short-term
overvoltage applied to the transformer,and a oscilloscope may
determine if
the input waveform is sinusoidal or otherwise,because 60hz iron core
tranformers don't like extreme distortion on their input,it gets
converted
to heat,not output voltage. a DMM will not show line distortion or
short
term overvoltages.
are the wires burned close to the transformer,or over their entire
length?

I peeled the insulation back from the hot and neutral wires and the
burning
only occurred right at the terminals, no more than 1/4" into the wiring.


Steve,

Not to be rude or anything, but a LOT of talk has gone on about your
problem
and I have not seen any further posts from you on the matter. No
comments about
any suggestions at all.

I'm not going to spend any more time on this thread until we hear back
from the
original poster with more information otherwise we are simply blowing
smoke
(sorry - couldn't resist).

John :-#)#

Just mentioned elsewhere that I have a new transformer on order and I
can't really do anything until that arrives. Rest assured I appreciate
all the input and I'm taking it all into consideration. Thanks.


Hi Steve,

Have you tried asking Trane themselves if they have a suggestion as to
the cause of the problem?

http://www.trane.com/Residential/Cus...Care/Feed-Back

Of course they may just send you to your local dealer, but it is worth a
try...

John :-#)#

--
(Please post followups or tech enquiries to the newsgroup)
John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9
Call (604)872-5757 or Fax 872-2010 (Pinballs, Jukes, Video Games)
www.flippers.com
"Old pinballers never die, they just flip out."

You make a lot of sense. As well as being comical. I agree,
that we don't have enough information to be sure. I have a
few guess what is wrong, but I'm also just guessing.

--
Christopher A. Young
Learn more about Jesus
www.lds.org
..


"John Robertson" wrote in message
...


I'm not going to spend any more time on this thread until we
hear back
from the original poster with more information otherwise we
are simply
blowing smoke (sorry - couldn't resist).

John :-#)#

On Thu, 14 Apr 2011 04:43:29 +0000 (UTC), (Don
Klipstein) wrote:

In m, D Nebenzahl wrote:
On 4/12/2011 9:23 PM Don Klipstein spake thus:

I have yet to look at these diagrams, but is the circuit board
powered by this tranny shown to "board level" as opposed to "component
level"? If so, then the board can have, probably does have, a rectifier
not shown in the diagram.

With all the pontificating you've been doing here, Don, I would've
thought you'd at least had glanced at the wiring diagrams the OP posted,
way up there somewhere. Sheesh.

The controller is shown as a block. It most certainly has at least one
rectifier on it, as it contains electronics that no doubt requires DC
power to operate. Thought you'd have figured it out. (Not just a relay
board.)

With such indication even as described here giving low indication as
to rectification having a 1-component bridge rectifier, 4 discrete diodes,
a fed-with-center-tap 2-diode fullwave scheme, 2 separate diodes or a
single 3-lead dual-diode used for that...

If the controller is only shown as a block, how well does it show the
rectifier scheme, as in whether the rectifier's diodes are discrete
individual diodes or integrated into one rectifier package?

If anyone here sees that noted to such extent that it's not a waste of
my time to take a look there, please pipe up!


The block diagram does not show it, but a picture of a replacement
board I found on the net seems to show 4 discrete diodes on the board
- which is what I have found on most control boards I have actually
had my hands on. Being a 2 wire transformer secondary, the center
tapped full wave scenario is a non-starter, leaving either a 4 wire
full wave bridge rectifier or 4 discrete diodes as the only real
options.

On Wed, 13 Apr 2011 23:19:22 -0600, Tony Hwang
wrote:



Phil Allison wrote:
"Vic Smith"
Steve Turner

Just mentioned elsewhere that I have a new transformer on order and I
can't
really do anything until that arrives. Rest assured I appreciate all the
input
and I'm taking it all into consideration. Thanks.

You bought the fuses, right?
I DON'T want to hear about another blown transformer.


** Be real smart for the OP to purchase some OTHER 120/24 volt tranny and
use it.

The things are a dime a dozen.

And fit a "slo-blo" 1/4 amp fuse to the primary.



.... Phil

Hmmm,
What is fuse gonna do? Instead of blowing x-former,, blow fuses?
Then still it is not right. Let;s go back from begining. How old
is the system? When this blowing tranny started? From day 1 or some
time(month, years after the system is installed? If tranny is hot to
touch when in use, that is rad flag.


A RAD flag - is that something like a "turkey timer" that pops up when
the rad overheats?

The fuse would hopefully pop first, saving the transformer long enough
to actually do some troubleshooting.

On 4/14/2011 12:41 AM, Smitty Two wrote:
In ,
Steve wrote:

Just mentioned elsewhere that I have a new transformer on order and I can't
really do anything until that arrives.

Sure you could. You could open up those other two transformers and check
for an open thermal fuse. As I recall, you said neither of them failed
in the same manner as the third. I still say you could have 3 distinct,
unrelated failures.

The design of the first transformer makes it virtually impossible to open it up
(remove the tape) without destroying the windings, (which I did) so there is no
possibility of "repairing" it by installing a thermal fuse (as some suggested).
There is evidence of burning at the input contactors just like there is on
the third transformer (the one I took pictures of), but not quite as bad. I
wouldn't call it an "explosion". There is no evidence of a thermal fuse.

On the second transformer (a completely different brand and style) there was no
evidence of burning. Again, it too was virtually impossible to open up with
destroying it, so I didn't bother. However, because everyone has been so
curious, I just did open it up (destroying it in the process) and there IS a
thermal fuse on the input side; it is open, which explains why there is no burning.

The third transformer is similar to the first in design (except for the extra
208 and 240 legs, which, per the instructions, I taped off and ignored). It is
also virtually impossible to remove the tape to gain access to the primary
windings without breaking through the wires, but I did, and again there is no
evidence of a thermal fuse.

I see no reason to conclude there are "3 distinct, unrelated failures".

In article ,
Steve Turner wrote:

On 4/14/2011 12:41 AM, Smitty Two wrote:
In ,
Steve wrote:

Just mentioned elsewhere that I have a new transformer on order and I
can't
really do anything until that arrives.

Sure you could. You could open up those other two transformers and check
for an open thermal fuse. As I recall, you said neither of them failed
in the same manner as the third. I still say you could have 3 distinct,
unrelated failures.

The design of the first transformer makes it virtually impossible to open it
up
(remove the tape) without destroying the windings, (which I did) so there is
no
possibility of "repairing" it by installing a thermal fuse (as some
suggested).
There is evidence of burning at the input contactors just like there is on
the third transformer (the one I took pictures of), but not quite as bad. I
wouldn't call it an "explosion". There is no evidence of a thermal fuse.

On the second transformer (a completely different brand and style) there was
no
evidence of burning. Again, it too was virtually impossible to open up with
destroying it, so I didn't bother. However, because everyone has been so
curious, I just did open it up (destroying it in the process) and there IS a
thermal fuse on the input side; it is open, which explains why there is no
burning.

The third transformer is similar to the first in design (except for the extra
208 and 240 legs, which, per the instructions, I taped off and ignored). It
is
also virtually impossible to remove the tape to gain access to the primary
windings without breaking through the wires, but I did, and again there is no
evidence of a thermal fuse.

I see no reason to conclude there are "3 distinct, unrelated failures".

Just because you can't fix something, it doesn't mean that failure
analysis is moot. I'd be doing serious exploratory surgery on all 3 of
those transformers to try to understand what the hell happened.

I'm not "concluding" that there are 3 distinct unrelated failures, I'm
suggesting it as a possibility.

The first, OEM transformer lasted 6 years. The second transformer lasted
a few days, and by your own admission was a cheap knockoff that may not
have been suited for your application at all.

And the 3rd transformer may well have failed due to improper wiring, or
a loose connection leading to excessive current leading to insulation
breakdown and a hard short, or as has been suggested repeatedly, a fault
somewhere on the secondary side.

You've also agreed that there are wire color discrepancies and several
respondents have opined that both halves of the primary should, perhaps,
have been wired in parallel to accommodate the current requirements.

So, I too am curious, have you acquired some appropriate fuses, figured
out how to monitor the current, and been able to schedule some time off
from your other responsibilities so that you can actually work through
this puzzle once the new xformer arrives? Are you equipped to bench test
the new transformer to verify wiring color scheme before you install it?
Do you know how to test that bridge rectifier? Seems like you have a
*lot* you could be doing while waiting for the UPS guy.

On 4/14/2011 12:06 PM, Smitty Two wrote:
In ,
Steve wrote:

On 4/14/2011 12:41 AM, Smitty Two wrote:
In ,
Steve wrote:

Just mentioned elsewhere that I have a new transformer on order and I
can't
really do anything until that arrives.

Sure you could. You could open up those other two transformers and check
for an open thermal fuse. As I recall, you said neither of them failed
in the same manner as the third. I still say you could have 3 distinct,
unrelated failures.

The design of the first transformer makes it virtually impossible to open it
up
(remove the tape) without destroying the windings, (which I did) so there is
no
possibility of "repairing" it by installing a thermal fuse (as some
suggested).
There is evidence of burning at the input contactors just like there is on
the third transformer (the one I took pictures of), but not quite as bad. I
wouldn't call it an "explosion". There is no evidence of a thermal fuse.

On the second transformer (a completely different brand and style) there was
no
evidence of burning. Again, it too was virtually impossible to open up with
destroying it, so I didn't bother. However, because everyone has been so
curious, I just did open it up (destroying it in the process) and there IS a
thermal fuse on the input side; it is open, which explains why there is no
burning.

The third transformer is similar to the first in design (except for the extra
208 and 240 legs, which, per the instructions, I taped off and ignored). It
is
also virtually impossible to remove the tape to gain access to the primary
windings without breaking through the wires, but I did, and again there is no
evidence of a thermal fuse.

I see no reason to conclude there are "3 distinct, unrelated failures".

Just because you can't fix something, it doesn't mean that failure
analysis is moot. I'd be doing serious exploratory surgery on all 3 of
those transformers to try to understand what the hell happened.

I'm not "concluding" that there are 3 distinct unrelated failures, I'm
suggesting it as a possibility.

The first, OEM transformer lasted 6 years. The second transformer lasted
a few days, and by your own admission was a cheap knockoff that may not
have been suited for your application at all.

Others sorta concluded that for me. It was "Made in China" and has a bit of a
different form factor, but that's the only evidence I have so say it might not
have been "suitable". The transformer was similarly rated, and internally it
doesn't look much different from the others, so I still have no real reason to
believe it shouldn't have worked.

And the 3rd transformer may well have failed due to improper wiring, or
a loose connection leading to excessive current leading to insulation
breakdown and a hard short, or as has been suggested repeatedly, a fault
somewhere on the secondary side.

You've also agreed that there are wire color discrepancies and several
respondents have opined that both halves of the primary should, perhaps,
have been wired in parallel to accommodate the current requirements.

I brought the old transformer to a local HVAC supply house, and the sales
person (whom I perceived to be at least somewhat of an expert), gave me the
third transformer as a suitable replacment. I chose to connect the transformer
according to the instructions, and not according to any speculation "opined" in
this group.

So, I too am curious, have you acquired some appropriate fuses, figured
out how to monitor the current, and been able to schedule some time off
from your other responsibilities so that you can actually work through
this puzzle once the new xformer arrives? Are you equipped to bench test
the new transformer to verify wiring color scheme before you install it?
Do you know how to test that bridge rectifier? Seems like you have a
*lot* you could be doing while waiting for the UPS guy.

I'm sorry you feel that I'm not "doing" anything or that I'm leaving you
hanging, but I'll be making the repairs on my own schedule, as time permits.
My own place of employ has me working 12 and 16 hour days, so I can't be
everywhere at once. Plus, the weather here is pleasant and there's been no
real need to run the air conditioner, and the house has two A/C units anyway so
I'm in no hurry. I don't have the fuses or fuse holders yet, but the
transformer isn't going in without them, so it will be taken care of. My
common sense tells me that I really shouldn't *have* to test and verify the
living daylights out of a new transformer, but I will most certainly get
bitched out here if I don't, so yes, that will be done. I don't really recall
the discussion about the bridge rectifier, but I'll look for it. I will be
reviewing the entire discussion and make a checklist of all the steps I need to
perform.

Anything else?

In article ,
Steve Turner wrote:

I chose to connect the transformer
according to the instructions, and not according to any speculation "opined"
in
this group.

Which instructions are those? You're not putting in an OEM transformer,
so you can't very well use the OEM instructions.

Carry on. My money's on you breaking out the Jewish toolbox pretty soon.
That's not a bad thing, but if you don't have the time or inclination to
DIY, there's no sense pretending you do.

On Apr 14, 2:37*pm, Steve Turner
wrote:
On 4/14/2011 12:06 PM, Smitty Two wrote:





In ,
* Steve *wrote:

On 4/14/2011 12:41 AM, Smitty Two wrote:
In ,
* *Steve * wrote:

Just mentioned elsewhere that I have a new transformer on order and I
can't
really do anything until that arrives.

Sure you could. You could open up those other two transformers and check
for an open thermal fuse. As I recall, you said neither of them failed
in the same manner as the third. I still say you could have 3 distinct,
unrelated failures.

The design of the first transformer makes it virtually impossible to open it
up
(remove the tape) without destroying the windings, (which I did) so there is
no
possibility of "repairing" it by installing a thermal fuse (as some
suggested).
* *There is evidence of burning at the input contactors just like there is on
the third transformer (the one I took pictures of), but not quite as bad. *I
wouldn't call it an "explosion". *There is no evidence of a thermal fuse.

On the second transformer (a completely different brand and style) there was
no
evidence of burning. *Again, it too was virtually impossible to open up with
destroying it, so I didn't bother. *However, because everyone has been so
curious, I just did open it up (destroying it in the process) and there IS a
thermal fuse on the input side; it is open, which explains why there is no
burning.

The third transformer is similar to the first in design (except for the extra
208 and 240 legs, which, per the instructions, I taped off and ignored). *It
is
also virtually impossible to remove the tape to gain access to the primary
windings without breaking through the wires, but I did, and again there is no
evidence of a thermal fuse.

I see no reason to conclude there are "3 distinct, unrelated failures"..

Just because you can't fix something, it doesn't mean that failure
analysis is moot. I'd be doing serious exploratory surgery on all 3 of
those transformers to try to understand what the hell happened.

I'm not "concluding" that there are 3 distinct unrelated failures, I'm
suggesting it as a possibility.

The first, OEM transformer lasted 6 years. The second transformer lasted
a few days, and by your own admission was a cheap knockoff that may not
have been suited for your application at all.

Others sorta concluded that for me. *It was "Made in China" and has a bit of a
different form factor, but that's the only evidence I have so say it might not
have been "suitable". *The transformer was similarly rated, and internally it
doesn't look much different from the others, so I still have no real reason to
believe it shouldn't have worked.

And the 3rd transformer may well have failed due to improper wiring, or
a loose connection leading to excessive current leading to insulation
breakdown and a hard short, or as has been suggested repeatedly, a fault
somewhere on the secondary side.

You've also agreed that there are wire color discrepancies and several
respondents have opined that both halves of the primary should, perhaps,
have been wired in parallel to accommodate the current requirements.

I brought the old transformer to a local HVAC supply house, and the sales
person (whom I perceived to be at least somewhat of an expert), gave me the
third transformer as a suitable replacment. *I chose to connect the transformer
according to the instructions, and not according to any speculation "opined" in
this group.

So, I too am curious, have you acquired some appropriate fuses, figured
out how to monitor the current, and been able to schedule some time off
from your other responsibilities so that *you can actually work through
this puzzle once the new xformer arrives? Are you equipped to bench test
the new transformer to verify wiring color scheme before you install it?
Do you know how to test that bridge rectifier? Seems like you have a
*lot* you could be doing while waiting for the UPS guy.

I'm sorry you feel that I'm not "doing" anything or that I'm leaving you
hanging, but I'll be making the repairs on my own schedule, as time permits.
My own place of employ has me working 12 and 16 hour days, so I can't be
everywhere at once. *Plus, the weather here is pleasant and there's been no
real need to run the air conditioner, and the house has two A/C units anyway so
I'm in no hurry. *I don't have the fuses or fuse holders yet, but the
transformer isn't going in without them, so it will be taken care of. *My
common sense tells me that I really shouldn't *have* to test and verify the
living daylights out of a new transformer, but I will most certainly get
bitched out here if I don't, so yes, that will be done. *I don't really recall
the discussion about the bridge rectifier, but I'll look for it. *I will be
reviewing the entire discussion and make a checklist of all the steps I need to
perform.

Anything else?- Hide quoted text -

- Show quoted text -

After you put it in, measure the current and voltages in both
the primary and secondary. I'd measure them both with the
AC running and with it not running.

Also, not sure if anyone ever covered this, but when the transformers
have failed have they all been in cooling mode, heating, or both?

On 4/14/2011 2:54 PM, wrote:
On Apr 14, 2:37 pm, Steve
wrote:
On 4/14/2011 12:06 PM, Smitty Two wrote:





In ,
Steve wrote:

On 4/14/2011 12:41 AM, Smitty Two wrote:
In ,
Steve wrote:

Just mentioned elsewhere that I have a new transformer on order and I
can't
really do anything until that arrives.

Sure you could. You could open up those other two transformers and check
for an open thermal fuse. As I recall, you said neither of them failed
in the same manner as the third. I still say you could have 3 distinct,
unrelated failures.

The design of the first transformer makes it virtually impossible to open it
up
(remove the tape) without destroying the windings, (which I did) so there is
no
possibility of "repairing" it by installing a thermal fuse (as some
suggested).
There is evidence of burning at the input contactors just like there is on
the third transformer (the one I took pictures of), but not quite as bad. I
wouldn't call it an "explosion". There is no evidence of a thermal fuse.

On the second transformer (a completely different brand and style) there was
no
evidence of burning. Again, it too was virtually impossible to open up with
destroying it, so I didn't bother. However, because everyone has been so
curious, I just did open it up (destroying it in the process) and there IS a
thermal fuse on the input side; it is open, which explains why there is no
burning.

The third transformer is similar to the first in design (except for the extra
208 and 240 legs, which, per the instructions, I taped off and ignored). It
is
also virtually impossible to remove the tape to gain access to the primary
windings without breaking through the wires, but I did, and again there is no
evidence of a thermal fuse.

I see no reason to conclude there are "3 distinct, unrelated failures".

Just because you can't fix something, it doesn't mean that failure
analysis is moot. I'd be doing serious exploratory surgery on all 3 of
those transformers to try to understand what the hell happened.

I'm not "concluding" that there are 3 distinct unrelated failures, I'm
suggesting it as a possibility.

The first, OEM transformer lasted 6 years. The second transformer lasted
a few days, and by your own admission was a cheap knockoff that may not
have been suited for your application at all.

Others sorta concluded that for me. It was "Made in China" and has a bit of a
different form factor, but that's the only evidence I have so say it might not
have been "suitable". The transformer was similarly rated, and internally it
doesn't look much different from the others, so I still have no real reason to
believe it shouldn't have worked.

And the 3rd transformer may well have failed due to improper wiring, or
a loose connection leading to excessive current leading to insulation
breakdown and a hard short, or as has been suggested repeatedly, a fault
somewhere on the secondary side.

You've also agreed that there are wire color discrepancies and several
respondents have opined that both halves of the primary should, perhaps,
have been wired in parallel to accommodate the current requirements.

I brought the old transformer to a local HVAC supply house, and the sales
person (whom I perceived to be at least somewhat of an expert), gave me the
third transformer as a suitable replacment. I chose to connect the transformer
according to the instructions, and not according to any speculation "opined" in
this group.

So, I too am curious, have you acquired some appropriate fuses, figured
out how to monitor the current, and been able to schedule some time off
from your other responsibilities so that you can actually work through
this puzzle once the new xformer arrives? Are you equipped to bench test
the new transformer to verify wiring color scheme before you install it?
Do you know how to test that bridge rectifier? Seems like you have a
*lot* you could be doing while waiting for the UPS guy.

I'm sorry you feel that I'm not "doing" anything or that I'm leaving you
hanging, but I'll be making the repairs on my own schedule, as time permits.
My own place of employ has me working 12 and 16 hour days, so I can't be
everywhere at once. Plus, the weather here is pleasant and there's been no
real need to run the air conditioner, and the house has two A/C units anyway so
I'm in no hurry. I don't have the fuses or fuse holders yet, but the
transformer isn't going in without them, so it will be taken care of. My
common sense tells me that I really shouldn't *have* to test and verify the
living daylights out of a new transformer, but I will most certainly get
bitched out here if I don't, so yes, that will be done. I don't really recall
the discussion about the bridge rectifier, but I'll look for it. I will be
reviewing the entire discussion and make a checklist of all the steps I need to
perform.

Anything else?- Hide quoted text -

- Show quoted text -

After you put it in, measure the current and voltages in both
the primary and secondary. I'd measure them both with the
AC running and with it not running.

Also, not sure if anyone ever covered this, but when the transformers
have failed have they all been in cooling mode, heating, or both?

Yep, I'll do that. It's only in cooling mode that the transformers have
failed, but I'm in Texas and we're long past the point where we'll be needing
the heater for a while, so it's hard to say whether or not running the heat
would also trigger the problem.

Steve Turner wrote:
On 4/14/2011 2:54 PM, wrote:
On Apr 14, 2:37 pm, Steve
wrote:
On 4/14/2011 12:06 PM, Smitty Two wrote:





In ,
Steve wrote:

On 4/14/2011 12:41 AM, Smitty Two wrote:
In ,
Steve wrote:

Just mentioned elsewhere that I have a new transformer on order
and I
can't
really do anything until that arrives.

Sure you could. You could open up those other two transformers and
check
for an open thermal fuse. As I recall, you said neither of them
failed
in the same manner as the third. I still say you could have 3
distinct,
unrelated failures.

The design of the first transformer makes it virtually impossible
to open it
up
(remove the tape) without destroying the windings, (which I did) so
there is
no
possibility of "repairing" it by installing a thermal fuse (as some
suggested).
There is evidence of burning at the input contactors just like
there is on
the third transformer (the one I took pictures of), but not quite
as bad. I
wouldn't call it an "explosion". There is no evidence of a thermal
fuse.

On the second transformer (a completely different brand and style)
there was
no
evidence of burning. Again, it too was virtually impossible to
open up with
destroying it, so I didn't bother. However, because everyone has
been so
curious, I just did open it up (destroying it in the process) and
there IS a
thermal fuse on the input side; it is open, which explains why
there is no
burning.

The third transformer is similar to the first in design (except for
the extra
208 and 240 legs, which, per the instructions, I taped off and
ignored). It
is
also virtually impossible to remove the tape to gain access to the
primary
windings without breaking through the wires, but I did, and again
there is no
evidence of a thermal fuse.

I see no reason to conclude there are "3 distinct, unrelated
failures".

Just because you can't fix something, it doesn't mean that failure
analysis is moot. I'd be doing serious exploratory surgery on all 3 of
those transformers to try to understand what the hell happened.

I'm not "concluding" that there are 3 distinct unrelated failures, I'm
suggesting it as a possibility.

The first, OEM transformer lasted 6 years. The second transformer
lasted
a few days, and by your own admission was a cheap knockoff that may not
have been suited for your application at all.

Others sorta concluded that for me. It was "Made in China" and has a
bit of a
different form factor, but that's the only evidence I have so say it
might not
have been "suitable". The transformer was similarly rated, and
internally it
doesn't look much different from the others, so I still have no real
reason to
believe it shouldn't have worked.

And the 3rd transformer may well have failed due to improper wiring, or
a loose connection leading to excessive current leading to insulation
breakdown and a hard short, or as has been suggested repeatedly, a
fault
somewhere on the secondary side.

You've also agreed that there are wire color discrepancies and several
respondents have opined that both halves of the primary should,
perhaps,
have been wired in parallel to accommodate the current requirements.

I brought the old transformer to a local HVAC supply house, and the
sales
person (whom I perceived to be at least somewhat of an expert), gave
me the
third transformer as a suitable replacment. I chose to connect the
transformer
according to the instructions, and not according to any speculation
"opined" in
this group.

So, I too am curious, have you acquired some appropriate fuses, figured
out how to monitor the current, and been able to schedule some time off
from your other responsibilities so that you can actually work through
this puzzle once the new xformer arrives? Are you equipped to bench
test
the new transformer to verify wiring color scheme before you install
it?
Do you know how to test that bridge rectifier? Seems like you have a
*lot* you could be doing while waiting for the UPS guy.

I'm sorry you feel that I'm not "doing" anything or that I'm leaving you
hanging, but I'll be making the repairs on my own schedule, as time
permits.
My own place of employ has me working 12 and 16 hour days, so I can't be
everywhere at once. Plus, the weather here is pleasant and there's
been no
real need to run the air conditioner, and the house has two A/C units
anyway so
I'm in no hurry. I don't have the fuses or fuse holders yet, but the
transformer isn't going in without them, so it will be taken care
of. My
common sense tells me that I really shouldn't *have* to test and
verify the
living daylights out of a new transformer, but I will most certainly get
bitched out here if I don't, so yes, that will be done. I don't
really recall
the discussion about the bridge rectifier, but I'll look for it. I
will be
reviewing the entire discussion and make a checklist of all the steps
I need to
perform.

Anything else?- Hide quoted text -

- Show quoted text -

After you put it in, measure the current and voltages in both
the primary and secondary. I'd measure them both with the
AC running and with it not running.

Also, not sure if anyone ever covered this, but when the transformers
have failed have they all been in cooling mode, heating, or both?

Yep, I'll do that. It's only in cooling mode that the transformers have
failed, but I'm in Texas and we're long past the point where we'll be
needing the heater for a while, so it's hard to say whether or not
running the heat would also trigger the problem.


Steve, As said before the best thing to do is to fuse both the primary
and secondary windings.

If you have the recommended (original) transformer ratings handy that
should make it easy to figure out. For example, if the secondary (24VAC
as I recall) is rated at 1A, then the primary fuse is 1/5 of that
(24:120 - plus a fudge factor) suggesting that a 0.25A slo-blo should
last fairly well, and a 1A slo-blo on the secondary winding. If the
secondary is rated at 2A, then I'd go with a 0.5A slo-blo on the
primary, along with a 2A slo-blo on the secondary.

Two fuse holders should be fine - one for the 120VAC side and one for
the 24VAC side.

Hope this helps - at least it will reduce the cost of replacing
transformers!

John :-#)#

--
(Please post followups or tech enquiries to the newsgroup)
John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9
Call (604)872-5757 or Fax 872-2010 (Pinballs, Jukes, Video Games)
www.flippers.com
"Old pinballers never die, they just flip out."

John Robertson wrote:
Steve Turner wrote:
On 4/14/2011 2:54 PM, wrote:
On Apr 14, 2:37 pm, Steve
wrote:
On 4/14/2011 12:06 PM, Smitty Two wrote:





In ,
Steve wrote:

On 4/14/2011 12:41 AM, Smitty Two wrote:
In ,
Steve wrote:

Just mentioned elsewhere that I have a new transformer on order
and I
can't
really do anything until that arrives.

Sure you could. You could open up those other two transformers
and check
for an open thermal fuse. As I recall, you said neither of them
failed
in the same manner as the third. I still say you could have 3
distinct,
unrelated failures.

The design of the first transformer makes it virtually impossible
to open it
up
(remove the tape) without destroying the windings, (which I did)
so there is
no
possibility of "repairing" it by installing a thermal fuse (as some
suggested).
There is evidence of burning at the input contactors just like
there is on
the third transformer (the one I took pictures of), but not quite
as bad. I
wouldn't call it an "explosion". There is no evidence of a thermal
fuse.

On the second transformer (a completely different brand and style)
there was
no
evidence of burning. Again, it too was virtually impossible to
open up with
destroying it, so I didn't bother. However, because everyone has
been so
curious, I just did open it up (destroying it in the process) and
there IS a
thermal fuse on the input side; it is open, which explains why
there is no
burning.

The third transformer is similar to the first in design (except
for the extra
208 and 240 legs, which, per the instructions, I taped off and
ignored). It
is
also virtually impossible to remove the tape to gain access to the
primary
windings without breaking through the wires, but I did, and again
there is no
evidence of a thermal fuse.

I see no reason to conclude there are "3 distinct, unrelated
failures".

Just because you can't fix something, it doesn't mean that failure
analysis is moot. I'd be doing serious exploratory surgery on all 3 of
those transformers to try to understand what the hell happened.

I'm not "concluding" that there are 3 distinct unrelated failures, I'm
suggesting it as a possibility.

The first, OEM transformer lasted 6 years. The second transformer
lasted
a few days, and by your own admission was a cheap knockoff that may
not
have been suited for your application at all.

Others sorta concluded that for me. It was "Made in China" and has a
bit of a
different form factor, but that's the only evidence I have so say it
might not
have been "suitable". The transformer was similarly rated, and
internally it
doesn't look much different from the others, so I still have no real
reason to
believe it shouldn't have worked.

And the 3rd transformer may well have failed due to improper
wiring, or
a loose connection leading to excessive current leading to insulation
breakdown and a hard short, or as has been suggested repeatedly, a
fault
somewhere on the secondary side.

You've also agreed that there are wire color discrepancies and several
respondents have opined that both halves of the primary should,
perhaps,
have been wired in parallel to accommodate the current requirements.

I brought the old transformer to a local HVAC supply house, and the
sales
person (whom I perceived to be at least somewhat of an expert), gave
me the
third transformer as a suitable replacment. I chose to connect the
transformer
according to the instructions, and not according to any speculation
"opined" in
this group.

So, I too am curious, have you acquired some appropriate fuses,
figured
out how to monitor the current, and been able to schedule some time
off
from your other responsibilities so that you can actually work through
this puzzle once the new xformer arrives? Are you equipped to bench
test
the new transformer to verify wiring color scheme before you
install it?
Do you know how to test that bridge rectifier? Seems like you have a
*lot* you could be doing while waiting for the UPS guy.

I'm sorry you feel that I'm not "doing" anything or that I'm leaving
you
hanging, but I'll be making the repairs on my own schedule, as time
permits.
My own place of employ has me working 12 and 16 hour days, so I
can't be
everywhere at once. Plus, the weather here is pleasant and there's
been no
real need to run the air conditioner, and the house has two A/C
units anyway so
I'm in no hurry. I don't have the fuses or fuse holders yet, but the
transformer isn't going in without them, so it will be taken care
of. My
common sense tells me that I really shouldn't *have* to test and
verify the
living daylights out of a new transformer, but I will most certainly
get
bitched out here if I don't, so yes, that will be done. I don't
really recall
the discussion about the bridge rectifier, but I'll look for it. I
will be
reviewing the entire discussion and make a checklist of all the
steps I need to
perform.

Anything else?- Hide quoted text -

- Show quoted text -

After you put it in, measure the current and voltages in both
the primary and secondary. I'd measure them both with the
AC running and with it not running.

Also, not sure if anyone ever covered this, but when the transformers
have failed have they all been in cooling mode, heating, or both?

Yep, I'll do that. It's only in cooling mode that the transformers
have failed, but I'm in Texas and we're long past the point where
we'll be needing the heater for a while, so it's hard to say whether
or not running the heat would also trigger the problem.


Steve, As said before the best thing to do is to fuse both the primary
and secondary windings.

If you have the recommended (original) transformer ratings handy that
should make it easy to figure out. For example, if the secondary (24VAC
as I recall) is rated at 1A, then the primary fuse is 1/5 of that
(24:120 - plus a fudge factor) suggesting that a 0.25A slo-blo should
last fairly well, and a 1A slo-blo on the secondary winding. If the
secondary is rated at 2A, then I'd go with a 0.5A slo-blo on the
primary, along with a 2A slo-blo on the secondary.

Two fuse holders should be fine - one for the 120VAC side and one for
the 24VAC side.

Hope this helps - at least it will reduce the cost of replacing
transformers!

John :-#)#

Hi,
Giving up for real solution? Just band aid fix? VChanging blown x-former
to blown fuse? If I am having problem like that I'd fix it for sure
dragging out all the tools I need. O'scope, clamp ammeter, DVM, etc.
Maybe it is asked already but is happening all of sudden or been like
that since the system got installed? Every symptom has cause.

On Thu, 14 Apr 2011 19:52:52 -0600, Tony Hwang
wrote:



John Robertson wrote:
Steve Turner wrote:
On 4/14/2011 2:54 PM, wrote:
On Apr 14, 2:37 pm, Steve
wrote:
On 4/14/2011 12:06 PM, Smitty Two wrote:





In ,
Steve wrote:

On 4/14/2011 12:41 AM, Smitty Two wrote:
In ,
Steve wrote:

Just mentioned elsewhere that I have a new transformer on order
and I
can't
really do anything until that arrives.

Sure you could. You could open up those other two transformers
and check
for an open thermal fuse. As I recall, you said neither of them
failed
in the same manner as the third. I still say you could have 3
distinct,
unrelated failures.

The design of the first transformer makes it virtually impossible
to open it
up
(remove the tape) without destroying the windings, (which I did)
so there is
no
possibility of "repairing" it by installing a thermal fuse (as some
suggested).
There is evidence of burning at the input contactors just like
there is on
the third transformer (the one I took pictures of), but not quite
as bad. I
wouldn't call it an "explosion". There is no evidence of a thermal
fuse.

On the second transformer (a completely different brand and style)
there was
no
evidence of burning. Again, it too was virtually impossible to
open up with
destroying it, so I didn't bother. However, because everyone has
been so
curious, I just did open it up (destroying it in the process) and
there IS a
thermal fuse on the input side; it is open, which explains why
there is no
burning.

The third transformer is similar to the first in design (except
for the extra
208 and 240 legs, which, per the instructions, I taped off and
ignored). It
is
also virtually impossible to remove the tape to gain access to the
primary
windings without breaking through the wires, but I did, and again
there is no
evidence of a thermal fuse.

I see no reason to conclude there are "3 distinct, unrelated
failures".

Just because you can't fix something, it doesn't mean that failure
analysis is moot. I'd be doing serious exploratory surgery on all 3 of
those transformers to try to understand what the hell happened.

I'm not "concluding" that there are 3 distinct unrelated failures, I'm
suggesting it as a possibility.

The first, OEM transformer lasted 6 years. The second transformer
lasted
a few days, and by your own admission was a cheap knockoff that may
not
have been suited for your application at all.

Others sorta concluded that for me. It was "Made in China" and has a
bit of a
different form factor, but that's the only evidence I have so say it
might not
have been "suitable". The transformer was similarly rated, and
internally it
doesn't look much different from the others, so I still have no real
reason to
believe it shouldn't have worked.

And the 3rd transformer may well have failed due to improper
wiring, or
a loose connection leading to excessive current leading to insulation
breakdown and a hard short, or as has been suggested repeatedly, a
fault
somewhere on the secondary side.

You've also agreed that there are wire color discrepancies and several
respondents have opined that both halves of the primary should,
perhaps,
have been wired in parallel to accommodate the current requirements.

I brought the old transformer to a local HVAC supply house, and the
sales
person (whom I perceived to be at least somewhat of an expert), gave
me the
third transformer as a suitable replacment. I chose to connect the
transformer
according to the instructions, and not according to any speculation
"opined" in
this group.

So, I too am curious, have you acquired some appropriate fuses,
figured
out how to monitor the current, and been able to schedule some time
off
from your other responsibilities so that you can actually work through
this puzzle once the new xformer arrives? Are you equipped to bench
test
the new transformer to verify wiring color scheme before you
install it?
Do you know how to test that bridge rectifier? Seems like you have a
*lot* you could be doing while waiting for the UPS guy.

I'm sorry you feel that I'm not "doing" anything or that I'm leaving
you
hanging, but I'll be making the repairs on my own schedule, as time
permits.
My own place of employ has me working 12 and 16 hour days, so I
can't be
everywhere at once. Plus, the weather here is pleasant and there's
been no
real need to run the air conditioner, and the house has two A/C
units anyway so
I'm in no hurry. I don't have the fuses or fuse holders yet, but the
transformer isn't going in without them, so it will be taken care
of. My
common sense tells me that I really shouldn't *have* to test and
verify the
living daylights out of a new transformer, but I will most certainly
get
bitched out here if I don't, so yes, that will be done. I don't
really recall
the discussion about the bridge rectifier, but I'll look for it. I
will be
reviewing the entire discussion and make a checklist of all the
steps I need to
perform.

Anything else?- Hide quoted text -

- Show quoted text -

After you put it in, measure the current and voltages in both
the primary and secondary. I'd measure them both with the
AC running and with it not running.

Also, not sure if anyone ever covered this, but when the transformers
have failed have they all been in cooling mode, heating, or both?

Yep, I'll do that. It's only in cooling mode that the transformers
have failed, but I'm in Texas and we're long past the point where
we'll be needing the heater for a while, so it's hard to say whether
or not running the heat would also trigger the problem.


Steve, As said before the best thing to do is to fuse both the primary
and secondary windings.

If you have the recommended (original) transformer ratings handy that
should make it easy to figure out. For example, if the secondary (24VAC
as I recall) is rated at 1A, then the primary fuse is 1/5 of that
(24:120 - plus a fudge factor) suggesting that a 0.25A slo-blo should
last fairly well, and a 1A slo-blo on the secondary winding. If the
secondary is rated at 2A, then I'd go with a 0.5A slo-blo on the
primary, along with a 2A slo-blo on the secondary.

Two fuse holders should be fine - one for the 120VAC side and one for
the 24VAC side.

Hope this helps - at least it will reduce the cost of replacing
transformers!

John :-#)#

Hi,
Giving up for real solution? Just band aid fix? VChanging blown x-former
to blown fuse? If I am having problem like that I'd fix it for sure
dragging out all the tools I need. O'scope, clamp ammeter, DVM, etc.
Maybe it is asked already but is happening all of sudden or been like
that since the system got installed? Every symptom has cause.
The fuse is not being put forward as a solution - just to avoid
blowing the transformer while finding the real problem.

First transformer apparently lasted several years - 6 I think from
what I remember of the post. - so no, it was not a problem from the
first install.

The fuse is not being put forward as a solution - just to avoid
blowing the transformer while finding the real problem.


** The fuse will actually help you diagnose the problem.

If the fuse opens soon as AC power is applied - the tranny is being
overloaded.

If the fuse opens after some time because insulation in the primary side has
failed, replacement fuses will open immediately despite the secondary being
disconnected.



....Phil

Phil Allison wrote:


The fuse is not being put forward as a solution - just to avoid
blowing the transformer while finding the real problem.


** The fuse will actually help you diagnose the problem.

If the fuse opens soon as AC power is applied - the tranny is being
overloaded.

If the fuse opens after some time because insulation in the primary side has
failed, replacement fuses will open immediately despite the secondary being
disconnected.



...Phil


Hmm,
This isunthinkab;e crazy idea but is the x-former being put in backward?
Rgwew i a such thing as current limiting x-formers. One thig I'd try
then I'd put in proper Wattage low value resister to lower the primary
voltage.

Phil Allison wrote:


The fuse is not being put forward as a solution - just to avoid
blowing the transformer while finding the real problem.


** The fuse will actually help you diagnose the problem.

If the fuse opens soon as AC power is applied - the tranny is being
overloaded.

If the fuse opens after some time because insulation in the primary side has
failed, replacement fuses will open immediately despite the secondary being
disconnected.



...Phil



Hi,
Another question, does he keep buying same x-former over and over or
something different little havier one? Along with fuse I'd put in series
a low value proper Wattage resistor to lower the primmary voltage little
bit. Crazy thinking but hope the x-former is not put in backward.

"Tony Hwang"


This isunthinkab;e crazy idea but is the x-former being put in backward?

** You must be totally schizo.

In ,
wrote:

SNIP stuff previously said

After you put it in, measure the current and voltages in both
the primary and secondary. I'd measure them both with the
AC running and with it not running.

Also, not sure if anyone ever covered this, but when the transformers
have failed have they all been in cooling mode, heating, or both?

Measure both AC and DC current through the secondary of the transformer.
If putting a multimeter into DC current mode gets a reading around or over
50 milliamps (,05 amp), then something is wrong with the load.
If DC secondary current is near or over 200 milliamps, then,
"Houston, we have a problem"! Probably with one of the recently-mentioned
discrete diodes in a board's bridge rectifier.

Ideally, DC current through transformer windings should be zero. With
exception to specialty cases, typically involving special transformers
that use DC-handling means such as gapped cores.

If this tranny is running into problems related to DC, look for DC
through the secondary. If that turns up substantially, then the
already-mentioned 4-discrete-diode bridge rectifier on the board is
likely to be the culprit. Look for solder joints there that need touching
up, or else replace the bad diode if one is found to be bad (or all 4 of
them), or the whole board.

Depending on ability and willingness to use a soldering iron and to
troubleshoot and repair a board to component level, even with pointers
to a suspect identified set of components on the board...
It may be more practical to get a replacement board if the existing one
causes substantial DC to flow through the secondary of the transformer
that is prone to failing.

--
- Don Klipstein )