I just bought a used Tektronix TM504 power module and would like to test
it before I put any plug-ins in. I plan to first ESR test any caps, then
check the pass transistors with a DMM diode test function, and finally
power it up and make sure all the voltages are in spec. Oh, and then
remove any inter-module jumpers and connector barriers. Is there anything
else I need to do?

I don't have a curve tracer to fully characterize the pass transistors. I
guess if it's necessary I could throw something together with a doorbell
transformer or whatever. I wouldn't be very good at interpreting the
graphs, though.

My DMM also has an hFE mode if that's any use.

Thanks for any assistance!

-- Adam

Adam Goldman wrote:
I just bought a used Tektronix TM504 power module and would like to test
it before I put any plug-ins in. I plan to first ESR test any caps, then
check the pass transistors with a DMM diode test function, and finally
power it up and make sure all the voltages are in spec. Oh, and then
remove any inter-module jumpers and connector barriers. Is there anything
else I need to do?

I don't have a curve tracer to fully characterize the pass transistors. I
guess if it's necessary I could throw something together with a doorbell
transformer or whatever. I wouldn't be very good at interpreting the
graphs, though.

My DMM also has an hFE mode if that's any use.

Thanks for any assistance!

-- Adam

Virtually every TM500 mainframe I've bought used had at least one bad
pass transistor.
Checking them with an ohm meter is definitely better than nothing.
But...they're often overheated for long periods of time.
On a curve tracer at high current, they can look more like resistors
than transistors.
Breakdown voltage can also come way down. Beta can go to hell, then the
driver in the plugin overheats and shorts out blowing up the plugin when
the voltage goes to the rail.

Also reheat all the transistor solder junctions. The heat tends to
crystalize the solder over a long time. Make sure the mounting nuts are
still tight.

I wouldn't sweat the ESR of the caps. Just put on a load and look at the
ripple. IIRC, full load minimum line should have a trough voltage of at
least 22V on the 25V supplies. Don't remember the number for the 11.5V,
but think it was 7V trough. But it's been three decades since I worried
about the numbers.
I've never seen a bad transformer, but expect they exist.

Take a good look at the connectors. Replace the plastic key. You
wouldn't think it important, but it helps guide the plugin so you don't
blow it up when you plug it in hot...at least not as often. Same thing
can happen if the top and bottom of the connector wears on the
fiberglass and lets the plugin slop up and down.

And use your expendable plugin to test the hole for the first time.
mike

--
Return address is VALID but some sites block emails
with links. Delete this sig when replying.
..
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mike wrote in :

Adam Goldman wrote:
I just bought a used Tektronix TM504 power module and would like to
test it before I put any plug-ins in. I plan to first ESR test any
caps, then check the pass transistors with a DMM diode test function,
and finally power it up and make sure all the voltages are in spec.
Oh, and then remove any inter-module jumpers and connector barriers.
Is there anything else I need to do?

I don't have a curve tracer to fully characterize the pass
transistors. I guess if it's necessary I could throw something
together with a doorbell transformer or whatever. I wouldn't be very
good at interpreting the graphs, though.

My DMM also has an hFE mode if that's any use.

Thanks for any assistance!

-- Adam

Virtually every TM500 mainframe I've bought used had at least one bad
pass transistor.
Checking them with an ohm meter is definitely better than nothing.
But...they're often overheated for long periods of time.
On a curve tracer at high current, they can look more like resistors
than transistors.
Breakdown voltage can also come way down. Beta can go to hell, then
the driver in the plugin overheats and shorts out blowing up the
plugin when the voltage goes to the rail.

Also reheat all the transistor solder junctions. The heat tends to
crystalize the solder over a long time. Make sure the mounting nuts
are still tight.

I wouldn't sweat the ESR of the caps. Just put on a load and look at
the ripple. IIRC, full load minimum line should have a trough voltage
of at least 22V on the 25V supplies. Don't remember the number for
the 11.5V, but think it was 7V trough. But it's been three decades
since I worried about the numbers.
I've never seen a bad transformer, but expect they exist.

Take a good look at the connectors. Replace the plastic key. You
wouldn't think it important, but it helps guide the plugin so you
don't blow it up when you plug it in hot...

You are NOT supposed to "hot" plug TM500/5K units.


at least not as often.
Same thing can happen if the top and bottom of the connector wears on
the fiberglass and lets the plugin slop up and down.

And use your expendable plugin to test the hole for the first time.
mike



There's a company that bought out TEK's TM500 product line
TEGAM;www.tegam.com


--
Jim Yanik
jyanik
at
kua.net

Jim Yanik wrote:
mike wrote in :


Adam Goldman wrote:

I just bought a used Tektronix TM504 power module and would like to
test it before I put any plug-ins in. I plan to first ESR test any
caps, then check the pass transistors with a DMM diode test function,
and finally power it up and make sure all the voltages are in spec.
Oh, and then remove any inter-module jumpers and connector barriers.
Is there anything else I need to do?

I don't have a curve tracer to fully characterize the pass
transistors. I guess if it's necessary I could throw something
together with a doorbell transformer or whatever. I wouldn't be very
good at interpreting the graphs, though.

My DMM also has an hFE mode if that's any use.

Thanks for any assistance!

-- Adam

Virtually every TM500 mainframe I've bought used had at least one bad
pass transistor.
Checking them with an ohm meter is definitely better than nothing.
But...they're often overheated for long periods of time.
On a curve tracer at high current, they can look more like resistors
than transistors.
Breakdown voltage can also come way down. Beta can go to hell, then
the driver in the plugin overheats and shorts out blowing up the
plugin when the voltage goes to the rail.

Also reheat all the transistor solder junctions. The heat tends to
crystalize the solder over a long time. Make sure the mounting nuts
are still tight.

I wouldn't sweat the ESR of the caps. Just put on a load and look at
the ripple. IIRC, full load minimum line should have a trough voltage
of at least 22V on the 25V supplies. Don't remember the number for
the 11.5V, but think it was 7V trough. But it's been three decades
since I worried about the numbers.
I've never seen a bad transformer, but expect they exist.

Take a good look at the connectors. Replace the plastic key. You
wouldn't think it important, but it helps guide the plugin so you
don't blow it up when you plug it in hot...


You are NOT supposed to "hot" plug TM500/5K units.

You are NOT supposed to spill coffee on your laptop.
You're NOT supposed to cut yourself shaving.
You're NOT supposed to drive your car into another.
You're NOT supposed...well...you get the point...$#!^ happens...
and having the key in place reduces the carnage when it does.
mike



at least not as often.
Same thing can happen if the top and bottom of the connector wears on
the fiberglass and lets the plugin slop up and down.

And use your expendable plugin to test the hole for the first time.
mike




There's a company that bought out TEK's TM500 product line
TEGAM;www.tegam.com





--
Return address is VALID but some sites block emails
with links. Delete this sig when replying.
..
Wanted, PCMCIA SCSI Card for HP m820 CDRW.
FS 500MHz Tek DSOscilloscope TDS540 Make Offer
Wanted, 12.1" LCD for Gateway Solo 5300. Samsung LT121SU-121
Bunch of stuff For Sale and Wanted at the link below.
MAKE THE OBVIOUS CHANGES TO THE LINK
htremovethistp://www.geocities.com/SiliconValley/Monitor/4710/

mike wrote in :

Jim Yanik wrote:
mike wrote in :


Take a good look at the connectors. Replace the plastic key. You
wouldn't think it important, but it helps guide the plugin so you
don't blow it up when you plug it in hot...


You are NOT supposed to "hot" plug TM500/5K units.

You are NOT supposed to spill coffee on your laptop.
You're NOT supposed to cut yourself shaving.
You're NOT supposed to drive your car into another.
You're NOT supposed...well...you get the point...$#!^ happens...
and having the key in place reduces the carnage when it does.
mike



Actually,it does not.
It all depends on which contacts are made first.

BTW,I worked for TEK for 21.5 years,testing,calibrating,and repairing TEK
test and measurement and video test equipment.I've worked on plenty of
TM500 items.




at least not as often.
Same thing can happen if the top and bottom of the connector wears on
the fiberglass and lets the plugin slop up and down.

And use your expendable plugin to test the hole for the first time.
mike




There's a company that bought out TEK's TM500 product line
TEGAM;www.tegam.com








--
Jim Yanik
jyanik
at
kua.net

Jim Yanik wrote:
mike wrote in :


Jim Yanik wrote:

mike wrote in :


Take a good look at the connectors. Replace the plastic key. You
wouldn't think it important, but it helps guide the plugin so you
don't blow it up when you plug it in hot...


You are NOT supposed to "hot" plug TM500/5K units.

You are NOT supposed to spill coffee on your laptop.
You're NOT supposed to cut yourself shaving.
You're NOT supposed to drive your car into another.
You're NOT supposed...well...you get the point...$#!^ happens...
and having the key in place reduces the carnage when it does.
mike




Actually,it does not.
It all depends on which contacts are made first.

You are absolutely correct...it depends. And you should ALWAYS turn off
the power before removing/inserting plugins.
The key wasn't designed as an alignment aid, and it doesn't provide much
help, and I didn't intend to overblow it's importance.

Color me conservative...


BTW,I worked for TEK for 21.5 years,testing,calibrating,and repairing TEK
test and measurement and video test equipment.I've worked on plenty of
TM500 items.

I defer to your experience. I was merely the engineering manager for
much of the TM500 stuff that came out in the mid 70's.
mike


--
Return address is VALID but some sites block emails
with links. Delete this sig when replying.
..
Wanted, PCMCIA SCSI Card for HP m820 CDRW.
FS 500MHz Tek DSOscilloscope TDS540 Make Offer
Wanted, 12.1" LCD for Gateway Solo 5300. Samsung LT121SU-121
Bunch of stuff For Sale and Wanted at the link below.
MAKE THE OBVIOUS CHANGES TO THE LINK
htremovethistp://www.geocities.com/SiliconValley/Monitor/4710/

mike wrote in :

Jim Yanik wrote:
mike wrote in
:


Jim Yanik wrote:

mike wrote in
:


Take a good look at the connectors. Replace the plastic key. You
wouldn't think it important, but it helps guide the plugin so you
don't blow it up when you plug it in hot...


You are NOT supposed to "hot" plug TM500/5K units.

You are NOT supposed to spill coffee on your laptop.
You're NOT supposed to cut yourself shaving.
You're NOT supposed to drive your car into another.
You're NOT supposed...well...you get the point...$#!^ happens...


and you're not supposed to use the CDROM tray as a cupholder! 8-)

and having the key in place reduces the carnage when it does.
mike




Actually,it does not.
It all depends on which contacts are made first.

You are absolutely correct...it depends. And you should ALWAYS turn
off the power before removing/inserting plugins.
The key wasn't designed as an alignment aid, and it doesn't provide
much help, and I didn't intend to overblow it's importance.

Color me conservative...


BTW,I worked for TEK for 21.5 years,testing,calibrating,and repairing
TEK test and measurement and video test equipment.I've worked on
plenty of TM500 items.

I defer to your experience. I was merely the engineering manager for
much of the TM500 stuff that came out in the mid 70's.
mike



FWIW,I often used to see those plastic keys crushed or completely missing
from the TM500 mainframes.(ham-handed techs!)

I also liked most of the TM500 line,except for those TM500 scopes;they were
useless,IMO.(displays too small,and lots of noise on the displayed signal.
We almost got stuck with SC504s for BENCH scopes back in the early
1980's,when our early 7K scopes were wearing out.(7504!!)

I worked in the Indy and Orlando field offices.
--
Jim Yanik
jyanik
at
kua.net

Jim Yanik wrote:
mike wrote in :


Jim Yanik wrote:

mike wrote in
:



Jim Yanik wrote:


mike wrote in
:

Take a good look at the connectors. Replace the plastic key. You
wouldn't think it important, but it helps guide the plugin so you
don't blow it up when you plug it in hot...


You are NOT supposed to "hot" plug TM500/5K units.

You are NOT supposed to spill coffee on your laptop.
You're NOT supposed to cut yourself shaving.
You're NOT supposed to drive your car into another.
You're NOT supposed...well...you get the point...$#!^ happens...



and you're not supposed to use the CDROM tray as a cupholder! 8-)


and having the key in place reduces the carnage when it does.
mike




Actually,it does not.
It all depends on which contacts are made first.

You are absolutely correct...it depends. And you should ALWAYS turn
off the power before removing/inserting plugins.
The key wasn't designed as an alignment aid, and it doesn't provide
much help, and I didn't intend to overblow it's importance.

Color me conservative...


BTW,I worked for TEK for 21.5 years,testing,calibrating,and repairing
TEK test and measurement and video test equipment.I've worked on
plenty of TM500 items.

I defer to your experience. I was merely the engineering manager for
much of the TM500 stuff that came out in the mid 70's.
mike




FWIW,I often used to see those plastic keys crushed or completely missing
from the TM500 mainframes.(ham-handed techs!)

Rough fiberglass edges wear out the key rapidly. More of a bad design
than user abuse.


I also liked most of the TM500 line,except for those TM500 scopes;they were
useless,IMO.(displays too small,and lots of noise on the displayed signal.
We almost got stuck with SC504s for BENCH scopes back in the early
1980's,when our early 7K scopes were wearing out.(7504!!)

I worked in the Indy and Orlando field offices.

The decisions were handed down from WAY up the chain.
It was always 10 pounds in a five pound sack. Compromises be darned.

But it was fun while it lasted.
mike
--
Return address is VALID but some sites block emails
with links. Delete this sig when replying.
..
Wanted, PCMCIA SCSI Card for HP m820 CDRW.
FS 500MHz Tek DSOscilloscope TDS540 Make Offer
Wanted, 12.1" LCD for Gateway Solo 5300. Samsung LT121SU-121
Bunch of stuff For Sale and Wanted at the link below.
MAKE THE OBVIOUS CHANGES TO THE LINK
htremovethistp://www.geocities.com/SiliconValley/Monitor/4710/

In article , mike wrote:
Virtually every TM500 mainframe I've bought used had at least one bad
pass transistor.
Checking them with an ohm meter is definitely better than nothing.
But...they're often overheated for long periods of time.
On a curve tracer at high current, they can look more like resistors
than transistors.
Breakdown voltage can also come way down. Beta can go to hell, then the
driver in the plugin overheats and shorts out blowing up the plugin when
the voltage goes to the rail.

Thanks for all the info!

The transistor junctions all measure about .54V drop one way and open the
other, on diode test. The high-power NPN is a little lower than the others.
I guess I'll still look into rigging up a curve tracer. How much
current/voltage do you usually have to put into them to make the problem
show?

There's not a cheap sub for these transistors if I just wanted to replace
them all preemptively, is there?

I wouldn't sweat the ESR of the caps.

I think you're right because on the two I checked it was too low to measure.
(No, the caps aren't shorted.) I still haven't gotten at the board to check
the others and reflow the solder. It looks like I'll have to remove half the
fasteners and panels in the unit?!

Just put on a load and look at the
ripple. IIRC, full load minimum line should have a trough voltage of at
least 22V on the 25V supplies. Don't remember the number for the 11.5V,
but think it was 7V trough. But it's been three decades since I worried
about the numbers.

I didn't see those numbers in the TM504 manual. Are they given in the
custom plugin kit manual or something?

Take a good look at the connectors. Replace the plastic key. You
wouldn't think it important, but it helps guide the plugin so you don't
blow it up when you plug it in hot...at least not as often. Same thing
can happen if the top and bottom of the connector wears on the
fiberglass and lets the plugin slop up and down.

The barriers appear to be in decent shape. Are replacements readily
available, anyway?

And use your expendable plugin to test the hole for the first time.

Uh-oh. I guess the DC504 will have to be the guinea pig.

BTW, my unit is too old to have the two 600V/1A anti polarity reversal
diodes shown in the manual addendum, so I'm going to put in 1N4007s
where they're shown in the schematic.

Thanks again for sharing your experience with me.

-- Adam

In article , mike wrote:
Jim Yanik wrote:
BTW,I worked for TEK for 21.5 years,testing,calibrating,and repairing TEK
test and measurement and video test equipment.I've worked on plenty of
TM500 items.
I defer to your experience. I was merely the engineering manager for
much of the TM500 stuff that came out in the mid 70's.
mike

Out of curiosity, do any of you Tek guys recognize the following initials,
from the "tested by" stickers in my plugins?

p. kelbey mw emf
jim mf emc
bob l es
gjs dt bjy
sm/dg bic elh

-- Adam

OSPAM (Adam Goldman) wrote in
:


Out of curiosity, do any of you Tek guys recognize the following
initials, from the "tested by" stickers in my plugins?

p. kelbey mw emf
jim mf emc
bob l es
gjs dt bjy
sm/dg bic elh

-- Adam


Sorry,no.

--
Jim Yanik
jyanik
at
kua.net

Adam Goldman wrote:
In article , mike wrote:

Virtually every TM500 mainframe I've bought used had at least one bad
pass transistor.
Checking them with an ohm meter is definitely better than nothing.
But...they're often overheated for long periods of time.
On a curve tracer at high current, they can look more like resistors
than transistors.
Breakdown voltage can also come way down. Beta can go to hell, then the
driver in the plugin overheats and shorts out blowing up the plugin when
the voltage goes to the rail.


Thanks for all the info!

The transistor junctions all measure about .54V drop one way and open the
other, on diode test. The high-power NPN is a little lower than the others.
I guess I'll still look into rigging up a curve tracer. How much
current/voltage do you usually have to put into them to make the problem
show?

There's not a cheap sub for these transistors if I just wanted to replace
them all preemptively, is there?


I wouldn't sweat the ESR of the caps.


I think you're right because on the two I checked it was too low to measure.
(No, the caps aren't shorted.) I still haven't gotten at the board to check
the others and reflow the solder. It looks like I'll have to remove half the
fasteners and panels in the unit?!


Just put on a load and look at the
ripple. IIRC, full load minimum line should have a trough voltage of at
least 22V on the 25V supplies. Don't remember the number for the 11.5V,
but think it was 7V trough. But it's been three decades since I worried
about the numbers.





I didn't see those numbers in the TM504 manual. Are they given in the
custom plugin kit manual or something?

Nope. You won't find 'em published, cause if you believe them, you'd
also have to believe that some of the early plugins won't always work.
Those numbers, assuming I remembered them correctly after 30 years,
are VERY conservative and very unlikely to occur in practice with a
random selection of plugins, but they guarantee everything will work and
were the guidelines for my design teams...IIRC.

mike


Take a good look at the connectors. Replace the plastic key. You
wouldn't think it important, but it helps guide the plugin so you don't
blow it up when you plug it in hot...at least not as often. Same thing
can happen if the top and bottom of the connector wears on the
fiberglass and lets the plugin slop up and down.


The barriers appear to be in decent shape. Are replacements readily
available, anyway?


And use your expendable plugin to test the hole for the first time.


Uh-oh. I guess the DC504 will have to be the guinea pig.

BTW, my unit is too old to have the two 600V/1A anti polarity reversal
diodes shown in the manual addendum, so I'm going to put in 1N4007s
where they're shown in the schematic.

Thanks again for sharing your experience with me.

-- Adam



--
Return address is VALID but some sites block emails
with links. Delete this sig when replying.
..
Wanted, PCMCIA SCSI Card for HP m820 CDRW.
FS 500MHz Tek DSOscilloscope TDS540 Make Offer
Wanted, 12.1" LCD for Gateway Solo 5300. Samsung LT121SU-121
Bunch of stuff For Sale and Wanted at the link below.
MAKE THE OBVIOUS CHANGES TO THE LINK
htremovethistp://www.geocities.com/SiliconValley/Monitor/4710/

mike wrote in :

Adam Goldman wrote:
In article , mike wrote:

Virtually every TM500 mainframe I've bought used had at least one bad
pass transistor.
Checking them with an ohm meter is definitely better than nothing.
But...they're often overheated for long periods of time.
On a curve tracer at high current, they can look more like resistors
than transistors.
Breakdown voltage can also come way down. Beta can go to hell, then
the driver in the plugin overheats and shorts out blowing up the
plugin when the voltage goes to the rail.


Thanks for all the info!

The transistor junctions all measure about .54V drop one way and open
the other, on diode test. The high-power NPN is a little lower than
the others. I guess I'll still look into rigging up a curve tracer.
How much current/voltage do you usually have to put into them to make
the problem show?

There's not a cheap sub for these transistors if I just wanted to
replace them all preemptively, is there?


I wouldn't sweat the ESR of the caps.


I think you're right because on the two I checked it was too low to
measure. (No, the caps aren't shorted.) I still haven't gotten at the
board to check the others and reflow the solder. It looks like I'll
have to remove half the fasteners and panels in the unit?!


Just put on a load and look at the
ripple. IIRC, full load minimum line should have a trough voltage of
at least 22V on the 25V supplies. Don't remember the number for the
11.5V, but think it was 7V trough. But it's been three decades since
I worried about the numbers.





I didn't see those numbers in the TM504 manual. Are they given in the
custom plugin kit manual or something?

Nope. You won't find 'em published, cause if you believe them, you'd
also have to believe that some of the early plugins won't always work.
Those numbers, assuming I remembered them correctly after 30 years,
are VERY conservative and very unlikely to occur in practice with a
random selection of plugins, but they guarantee everything will work
and were the guidelines for my design teams...IIRC.

mike


Take a good look at the connectors. Replace the plastic key. You
wouldn't think it important, but it helps guide the plugin so you
don't blow it up when you plug it in hot...at least not as often.
Same thing can happen if the top and bottom of the connector wears on
the fiberglass and lets the plugin slop up and down.


The barriers appear to be in decent shape. Are replacements readily
available, anyway?


And use your expendable plugin to test the hole for the first time.


Uh-oh. I guess the DC504 will have to be the guinea pig.

BTW, my unit is too old to have the two 600V/1A anti polarity
reversal diodes shown in the manual addendum, so I'm going to put in
1N4007s where they're shown in the schematic.

Thanks again for sharing your experience with me.

-- Adam




TEK actually made an 067-xxxx-99 fixture for testing TM500 mainframes,it
checked each slot individually,measured load and no-load voltages and
ripple using a DMM,scope,and external load resistors.It came with a brief
pamphlet with procedure and voltage/ripple charts for each TM500
mainframe(1-wide,3-wide,4 wide,5-wide,6-wide),measured the transistors
beta.It was never sold outside of TEK.(It also was not ISO-9000 compliant)

I suspect the remaining TEK service centers(Factory and DC) have several of
them,and the data sheet,and still use them.I know Orlando's was shipped to
DC.

--
Jim Yanik
jyanik
at
kua.net