Fosdex multi-tracker / mixer with HDD and CD drive landed on the bench with
the reported fault of "Won't power up. When it last did, smoked"

Once opened, the problem was immediately apparent in that every secondary
side electrolytic on its switchmode power supply, was bulging to a greater
or lesser degree, with a couple of them gone to the point of the top having
split, and spewed electrolyte - the ones behind the reported smoke, I would
guess.

Having noted all the values, I removed them all (13 in total !), in
readiness to do a blanket replacement. Just for sport, I decided to run the
ESR meter over them to see just how bad they were. And this is where it got
odd ...

A couple of them were well out of spec, as you would expect when confronted
by a bulging can, but for the most part, all of them had an acceptable ESR
figure, including the 'exploded' ones. So I got out the capacitance meter
and ran that over them all. This time, almost without exception, all were
low or very low in value, including the two split ones, which were the
better part of open circuit. This was all quite the contrary of what I had
expected. In many cases in the past, I have found electrolytics which
exhibited a very high ESR, but whose value was just about spot on. I don't
recall ever seeing it the other way round though, like this. It's actually
hard to see how a cap can exhibit a perfect ESR, and yet have a value that
has dropped to less than half its marked nominal.

And aside from this, how on earth can every secondary side cap fail in this
way, and all at about the same time? It's not as though most of them are
placed in the designers' favourite spot of next to a heatsink or power
resistor. Neither is the interior of the unit particularly compact. I
wouldn't have thought that the temperature inside the case would get much
above ambient. I can only assume that the caps that have been used, are
either very badly specced, or of extremely poor quality.

Arfa

In article ,
Arfa Daily wrote:

And aside from this, how on earth can every secondary side cap fail in this
way, and all at about the same time? It's not as though most of them are
placed in the designers' favourite spot of next to a heatsink or power
resistor. Neither is the interior of the unit particularly compact. I
wouldn't have thought that the temperature inside the case would get much
above ambient. I can only assume that the caps that have been used, are
either very badly specced, or of extremely poor quality.

Any chance that an upstream failure exposed these caps to excessive
voltage? If the switch regulator's sensing feedback loop were to
fail, the switcher might have "stuck on", and ended up pumping the raw
incoming voltage into the secondary rails?

--
Dave Platt AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

"Arfa Daily" wrote in message
...
Fosdex multi-tracker / mixer with HDD and CD drive landed on the bench
with the reported fault of "Won't power up. When it last did, smoked"

Once opened, the problem was immediately apparent in that every secondary
side electrolytic on its switchmode power supply, was bulging to a greater
or lesser degree, with a couple of them gone to the point of the top
having split, and spewed electrolyte - the ones behind the reported smoke,
I would guess.

Having noted all the values, I removed them all (13 in total !), in
readiness to do a blanket replacement. Just for sport, I decided to run
the ESR meter over them to see just how bad they were. And this is where
it got odd ...

A couple of them were well out of spec, as you would expect when
confronted by a bulging can, but for the most part, all of them had an
acceptable ESR figure, including the 'exploded' ones. So I got out the
capacitance meter and ran that over them all. This time, almost without
exception, all were low or very low in value, including the two split
ones, which were the better part of open circuit. This was all quite the
contrary of what I had expected. In many cases in the past, I have found
electrolytics which exhibited a very high ESR, but whose value was just
about spot on. I don't recall ever seeing it the other way round though,
like this. It's actually hard to see how a cap can exhibit a perfect ESR,
and yet have a value that has dropped to less than half its marked
nominal.

And aside from this, how on earth can every secondary side cap fail in
this way, and all at about the same time? It's not as though most of them
are placed in the designers' favourite spot of next to a heatsink or power
resistor. Neither is the interior of the unit particularly compact. I
wouldn't have thought that the temperature inside the case would get much
above ambient. I can only assume that the caps that have been used, are
either very badly specced, or of extremely poor quality.

Arfa

One or two caps develop enough ESR to cause a regulation problem, duty cycle
increases to compensate for the "low" DC level, the actual DC runs away,
caps are exposed to over-voltage, then vent.

Just like old Panasonic VCR's. Often only one line 5 volt for example, is
monitored for regulation purposes.

Mark Z.

"Dave Platt" wrote in message
...
In article ,
Arfa Daily wrote:

And aside from this, how on earth can every secondary side cap fail in
this
way, and all at about the same time? It's not as though most of them are
placed in the designers' favourite spot of next to a heatsink or power
resistor. Neither is the interior of the unit particularly compact. I
wouldn't have thought that the temperature inside the case would get much
above ambient. I can only assume that the caps that have been used, are
either very badly specced, or of extremely poor quality.

Any chance that an upstream failure exposed these caps to excessive
voltage? If the switch regulator's sensing feedback loop were to
fail, the switcher might have "stuck on", and ended up pumping the raw
incoming voltage into the secondary rails?

--


How about loss of a single diode, short or open and the resulting AC applied
to the caps.

"Mark Zacharias" wrote in message
.com...
"Arfa Daily" wrote in message
...
Fosdex multi-tracker / mixer with HDD and CD drive landed on the bench
with the reported fault of "Won't power up. When it last did, smoked"

Once opened, the problem was immediately apparent in that every secondary
side electrolytic on its switchmode power supply, was bulging to a
greater or lesser degree, with a couple of them gone to the point of the
top having split, and spewed electrolyte - the ones behind the reported
smoke, I would guess.

Having noted all the values, I removed them all (13 in total !), in
readiness to do a blanket replacement. Just for sport, I decided to run
the ESR meter over them to see just how bad they were. And this is where
it got odd ...

A couple of them were well out of spec, as you would expect when
confronted by a bulging can, but for the most part, all of them had an
acceptable ESR figure, including the 'exploded' ones. So I got out the
capacitance meter and ran that over them all. This time, almost without
exception, all were low or very low in value, including the two split
ones, which were the better part of open circuit. This was all quite the
contrary of what I had expected. In many cases in the past, I have found
electrolytics which exhibited a very high ESR, but whose value was just
about spot on. I don't recall ever seeing it the other way round though,
like this. It's actually hard to see how a cap can exhibit a perfect ESR,
and yet have a value that has dropped to less than half its marked
nominal.

And aside from this, how on earth can every secondary side cap fail in
this way, and all at about the same time? It's not as though most of them
are placed in the designers' favourite spot of next to a heatsink or
power resistor. Neither is the interior of the unit particularly compact.
I wouldn't have thought that the temperature inside the case would get
much above ambient. I can only assume that the caps that have been used,
are either very badly specced, or of extremely poor quality.

Arfa

One or two caps develop enough ESR to cause a regulation problem, duty
cycle increases to compensate for the "low" DC level, the actual DC runs
away, caps are exposed to over-voltage, then vent.

Just like old Panasonic VCR's. Often only one line 5 volt for example, is
monitored for regulation purposes.

Mark Z.

All good points from everyone. I will find out later today if any additional
probs, as I did not have enough 470uF caps in stock, so had to order some
more. I'm leaning towards Mark's theory, because I've seen it before now I
come to think about it, and interestingly, the caps that had failed most
badly, were a pair of parallelled 1200uF's on the main rail, which is
probably the one used as the reference for the control loop. If that is the
case, then here's hoping that the rest of the rails didn't go too wild
before it all fell over completely. I have seen downstream circuitry damaged
beyond sensible rescue, by this kind of failure in cheapo supermarket DVD
players employing really cheap and nasty power supplies ... :-\

I'll let y'all know ...

Arfa

On Tue, 26 Oct 2010 22:24:05 -0400, "tm"
wrote:


"Dave Platt" wrote in message
...
...

Any chance that an upstream failure exposed these caps to excessive
voltage? If the switch regulator's sensing feedback loop were to
fail, the switcher might have "stuck on", and ended up pumping the raw
incoming voltage into the secondary rails?

--


How about loss of a single diode, short or open and the resulting AC applied
to the caps.


I'm reminded of the brain dead day I had a modem with a blown bridge
in the powersupply. Was four individual diodes, and I grabbed what I
thought were four standard Si diodes with the right current ratings.

To teach me to not think, fate substituted 5.1 volt zener diodes for
what I thought were rectifiers, and the results were, shall we say,
unexpected!

The only good thing was that once I replaced the zeners with regular
diodes, replaced the now blown regulator with a new one, it all came
back to life--but you can be sure I don't use poorly marked parts
without carefully checking to see what they are.

I have to agree, I think something other than just defective
capacitors is at work here--likely either an overvoltage or A/C is
getting into the caps and killing 'em.

On Tue, 26 Oct 2010 20:46:19 -0500, Mark Zacharias wrote:

Just like old Panasonic VCR's. Often only one line 5 volt for example,
is monitored for regulation purposes.

Mark Z.

Thanks for reminding me of those. Well not really thanks but more like
DAMMIT! Turned me off from Panasonic electronics for a long time.



--
Live Fast, Die Young and Leave a Pretty Corpse

Arfa Daily wrote:
Fosdex multi-tracker / mixer with HDD and CD drive landed on the bench with
the reported fault of "Won't power up. When it last did, smoked"

Once opened, the problem was immediately apparent in that every secondary
side electrolytic on its switchmode power supply, was bulging to a greater
or lesser degree, with a couple of them gone to the point of the top having
split, and spewed electrolyte - the ones behind the reported smoke, I would
guess.

Having noted all the values, I removed them all (13 in total !), in
readiness to do a blanket replacement. Just for sport, I decided to run the
ESR meter over them to see just how bad they were. And this is where it got
odd ...

I recently repaired a couple of powerline LAN adapters with about the same
defect, secondary SMPS electrolytics bulging (and SMPS not working anymore
however).
I always test for low ESR all electrolytics and all tested good, including
the bulging ones.
Replacing them however revived the SMPS.
I didn't test them for capacity, I just remember I was surprised by this
result.
Indeed the first time a bad electrolytic tests good with the ESR meter with
me.
I tend to believe the original capacitor were of very low quality (and/or
the design of the device was indeed bad) as both the units failed about
in the same week in their first summer of life (T 30C here in the summer).

Regards

Frank IZ8DWF

"Arfa Daily" wrote in
:

Fosdex multi-tracker / mixer with HDD and CD drive landed on the bench
with the reported fault of "Won't power up. When it last did, smoked"

Once opened, the problem was immediately apparent in that every
secondary side electrolytic on its switchmode power supply, was
bulging to a greater or lesser degree, with a couple of them gone to
the point of the top having split, and spewed electrolyte - the ones
behind the reported smoke, I would guess.

Having noted all the values, I removed them all (13 in total !), in
readiness to do a blanket replacement. Just for sport, I decided to
run the ESR meter over them to see just how bad they were. And this is
where it got odd ...

A couple of them were well out of spec, as you would expect when
confronted by a bulging can, but for the most part, all of them had an
acceptable ESR figure, including the 'exploded' ones. So I got out the
capacitance meter and ran that over them all. This time, almost
without exception, all were low or very low in value, including the
two split ones, which were the better part of open circuit. This was
all quite the contrary of what I had expected. In many cases in the
past, I have found electrolytics which exhibited a very high ESR, but
whose value was just about spot on. I don't recall ever seeing it the
other way round though, like this. It's actually hard to see how a cap
can exhibit a perfect ESR, and yet have a value that has dropped to
less than half its marked nominal.

And aside from this, how on earth can every secondary side cap fail in
this way, and all at about the same time? It's not as though most of
them are placed in the designers' favourite spot of next to a heatsink
or power resistor. Neither is the interior of the unit particularly
compact. I wouldn't have thought that the temperature inside the case
would get much above ambient. I can only assume that the caps that
have been used, are either very badly specced, or of extremely poor
quality.

Arfa



I had a TEK 1700 switcher supply that regulated on the +5V rail,and when
the +5V filter cap's ESR went high,the other rails drove up,for example the
+40 went to +63,and then the HV osc xstr running off the +40 began cooking
the PCB around it's leads until it because a short and caused the PS to
current limit(burst mode).Many of the secondary PS electrolytics were
cooked to some degree.

Some other TEK instruments had similar problems.(all switchers)

--
Jim Yanik
jyanik
at
localnet
dot com

"tm" wrote in
:


"Dave Platt" wrote in message
...
In article ,
Arfa Daily wrote:

And aside from this, how on earth can every secondary side cap fail
in this
way, and all at about the same time? It's not as though most of them
are placed in the designers' favourite spot of next to a heatsink or
power resistor. Neither is the interior of the unit particularly
compact. I wouldn't have thought that the temperature inside the case
would get much above ambient. I can only assume that the caps that
have been used, are either very badly specced, or of extremely poor
quality.

Any chance that an upstream failure exposed these caps to excessive
voltage? If the switch regulator's sensing feedback loop were to
fail, the switcher might have "stuck on", and ended up pumping the
raw incoming voltage into the secondary rails?

--


How about loss of a single diode, short or open and the resulting AC
applied to the caps.



usually a shorted diode causes a current limit problem.
(burst,"click" or "chirp" mode)
I haven't seem many open secondary rect. diodes in switchers.

--
Jim Yanik
jyanik
at
localnet
dot com

On Thu, 28 Oct 2010 02:25:28 +0100, "Arfa Daily"
wrote:

The one
originally fitted to the unit is a 40 GB Western Digital. Of the drives I
had, the three very old ones were all much smaller than that, and the newer
one, much bigger at 250 GB.

What model? My guess would be MR8HD.
http://pro-audio.musiciansfriend.com/product/Fostex-MR8HD-CD-8Track-Recorder-with-CDR?sku=247120
If so, it's FAT32 and the internal formatter should work. Just plop
in a drive, do the format, and you're done. There's probably an upper
limit to the size drive it will handle. 250GB is probably too new and
too much.

But the question now is, does the unit require a
specific make and size of drive in it ?

No. Nothing specific. Find the model number on the blown WD drive
and see if it's some kind of special.

Keep going, you're doing nicely. However, I hate to see the bill for
this repair.


--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

"Jeff Liebermann" wrote in message
...
On Thu, 28 Oct 2010 02:25:28 +0100, "Arfa Daily"
wrote:

The one
originally fitted to the unit is a 40 GB Western Digital. Of the drives I
had, the three very old ones were all much smaller than that, and the
newer
one, much bigger at 250 GB.

What model? My guess would be MR8HD.
http://pro-audio.musiciansfriend.com/product/Fostex-MR8HD-CD-8Track-Recorder-with-CDR?sku=247120
If so, it's FAT32 and the internal formatter should work. Just plop
in a drive, do the format, and you're done. There's probably an upper
limit to the size drive it will handle. 250GB is probably too new and
too much.

But the question now is, does the unit require a
specific make and size of drive in it ?

No. Nothing specific. Find the model number on the blown WD drive
and see if it's some kind of special.

Keep going, you're doing nicely. However, I hate to see the bill for
this repair.


--
Jeff Liebermann


Yes Jeff. All my thoughts exactly. The original drive is definitely bad. I
unscrewed its board, and a pinhole is blown in the top of what is probably
the platen motor drive chip. The foam padding above it has a nice burn mark
....

It's a "Caviar" series, specifically model WD400BB. My mate's shop should
be open now. I'll call him in a minute, and see what he's got.

The bill for this repair is a bit of a tricky one. The phone number that the
shop took down for the owner is wrong, so they can't get hold of him, and he
hasn't rung chasing it yet. Based on the value of the unit (not huge, but
enough that you wouldn't want to have to replace it from new again if you
could help it) and also what appeared on the surface to be wrong with it,
the shop have already made an 'executive' decision and given me an 'up to'
price. If I can pick up a second hand drive that works in it from my mate,
then I can probably still scrape into that figure, but it's gonna be close.
I'm sure with all your experience in the service field, that like me, you
come across situations like this all the time where it's a case of gritting
your teeth and carrying on for 'just a few more minutes ... ' The trick is
to determine when you really are swimming against a retreating tide. This
one is getting close to that :-|

Arfa

On Thu, 28 Oct 2010 09:17:08 +0100 "Arfa Daily"
wrote in Message id: :



"Jeff Liebermann" wrote in message
.. .
On Thu, 28 Oct 2010 02:25:28 +0100, "Arfa Daily"
wrote:

The one
originally fitted to the unit is a 40 GB Western Digital. Of the drives I
had, the three very old ones were all much smaller than that, and the
newer
one, much bigger at 250 GB.

What model? My guess would be MR8HD.
http://pro-audio.musiciansfriend.com/product/Fostex-MR8HD-CD-8Track-Recorder-with-CDR?sku=247120
If so, it's FAT32 and the internal formatter should work. Just plop
in a drive, do the format, and you're done. There's probably an upper
limit to the size drive it will handle. 250GB is probably too new and
too much.

But the question now is, does the unit require a
specific make and size of drive in it ?

No. Nothing specific. Find the model number on the blown WD drive
and see if it's some kind of special.

Keep going, you're doing nicely. However, I hate to see the bill for
this repair.


--
Jeff Liebermann


Yes Jeff. All my thoughts exactly. The original drive is definitely bad. I
unscrewed its board, and a pinhole is blown in the top of what is probably
the platen motor drive chip. The foam padding above it has a nice burn mark
...

It's a "Caviar" series, specifically model WD400BB. My mate's shop should
be open now. I'll call him in a minute, and see what he's got.

Just guessing of course, but I would think a hard drive limitation of
137GB (Greater than this requires LBA48 support) might be where the
ceiling is on the piece you're working on. If you can't get the exact
model you need, try using any drive between 20GB and 120GB. Also, see if
the 250GB drive you have has a capacity limit jumper.

snip


Arfa

The IDE controller and the BIOS of the unit probably doesn't do 48 bit LBA
so you might try to jumper a drive to limit its size to 137 GB or less.
My Fostex D90 won't see anything past 4.3GB even with a 10GB installed
but it still operates at 4.3GB. But then there is no limitation of 48 BIT
translation as the old drives less that 137 GB use 28 bit logical block
addressing. Just a thought.



--
Live Fast, Die Young and Leave a Pretty Corpse

Well, it's all a bit academic now ... My mate had just had a huge clearout,
and dumped all his 'recovered' drives, but he rang another friend who is a
PC recycler, and he said that he had 40 gig drives coming out of his ears,
and I was welcome to one for free, if I wanted to go over to his place to
pick one up. So I made the 20 mile round trip, and picked a drive up. I hung
it in the unit, got the error message with a request to format the drive,
started that going, and Lo ! - it did it in about 2 seconds flat. Result ! I
thought ...

However, with an input on any channel, there was no response - no signal
presence light, no peak light, no dancing segments in the display. A few
voltage measurements determined that the PSU was not outputting any +15v to
the analogue input board, so back out it came. 4R7 sm resistor in the feed
to the +15v regulator transistor was open. The transistor itself was also
short circuit, and the zener. After replacing these, the +15v was back, but
still no response from the analogue board, so I guess that the opamps on
there had probably been ****ted as the psu failed. This brought me to the
point of serious debate as to whether it was worth carrying on. This issue
was promptly resolved by a slip of the meter probe when the phone rang and
startled me. The +48v phantom feed goes up to the analogue board, along with
+ / - 15v and +5v. Guess which pin the 48v is right next to ...? Yep, the
5v, and the very next place it goes is the hard drive. "Squeal - squeal -
squeal " goes the replacement HDD, as the mouse that runs it inside, is
electrocuted ...

With a sigh, I reached for the pot of screws, and put it all back together.
Some faults are just not intended to be repaired. To be honest, I had
reservations about this right from the start, but when work is quiet, and
you are presented with what looks like a straightforward problem, it's easy
to get sucked in. Note to myself. Trust your instincts, boy ... :-(

Arfa

"Arfa Daily" wrote in message
...

snip


Arfa

The IDE controller and the BIOS of the unit probably doesn't do 48 bit
LBA
so you might try to jumper a drive to limit its size to 137 GB or less.
My Fostex D90 won't see anything past 4.3GB even with a 10GB installed
but it still operates at 4.3GB. But then there is no limitation of 48 BIT
translation as the old drives less that 137 GB use 28 bit logical block
addressing. Just a thought.



--
Live Fast, Die Young and Leave a Pretty Corpse

Well, it's all a bit academic now ... My mate had just had a huge
clearout, and dumped all his 'recovered' drives, but he rang another
friend who is a PC recycler, and he said that he had 40 gig drives coming
out of his ears, and I was welcome to one for free, if I wanted to go over
to his place to pick one up. So I made the 20 mile round trip, and picked
a drive up. I hung it in the unit, got the error message with a request to
format the drive, started that going, and Lo ! - it did it in about 2
seconds flat. Result ! I thought ...

However, with an input on any channel, there was no response - no signal
presence light, no peak light, no dancing segments in the display. A few
voltage measurements determined that the PSU was not outputting any +15v
to the analogue input board, so back out it came. 4R7 sm resistor in the
feed to the +15v regulator transistor was open. The transistor itself was
also short circuit, and the zener. After replacing these, the +15v was
back, but still no response from the analogue board, so I guess that the
opamps on there had probably been ****ted as the psu failed. This brought
me to the point of serious debate as to whether it was worth carrying on.
This issue was promptly resolved by a slip of the meter probe when the
phone rang and startled me. The +48v phantom feed goes up to the analogue
board, along with + / - 15v and +5v. Guess which pin the 48v is right next
to ...? Yep, the 5v, and the very next place it goes is the hard drive.
"Squeal - squeal - squeal " goes the replacement HDD, as the mouse that
runs it inside, is electrocuted ...

With a sigh, I reached for the pot of screws, and put it all back
together. Some faults are just not intended to be repaired. To be honest,
I had reservations about this right from the start, but when work is
quiet, and you are presented with what looks like a straightforward
problem, it's easy to get sucked in. Note to myself. Trust your instincts,
boy ... :-(

Arfa


Wow. Like you said, it seems some repairs are just not meant to be...

I once traced down a bad resistor in a Yamaha protection circuit voltage
divider, which had resulted in falsely triggering the protect circuit. Lots
of time and labor expense.

A couple weeks later, the customer's house had a lightning strike, the
receiver was severely damaged.

Just not meant to be...


Mark Z.

On Fri, 29 Oct 2010 02:36:06 +0100, Arfa Daily wrote:

snip


Arfa

The IDE controller and the BIOS of the unit probably doesn't do 48 bit
LBA so you might try to jumper a drive to limit its size to 137 GB or
less. My Fostex D90 won't see anything past 4.3GB even with a 10GB
installed but it still operates at 4.3GB. But then there is no
limitation of 48 BIT translation as the old drives less that 137 GB use
28 bit logical block addressing. Just a thought.



--
Live Fast, Die Young and Leave a Pretty Corpse

Well, it's all a bit academic now ... My mate had just had a huge
clearout, and dumped all his 'recovered' drives, but he rang another
friend who is a PC recycler, and he said that he had 40 gig drives
coming out of his ears, and I was welcome to one for free, if I wanted
to go over to his place to pick one up. So I made the 20 mile round
trip, and picked a drive up. I hung it in the unit, got the error
message with a request to format the drive, started that going, and Lo !
- it did it in about 2 seconds flat. Result ! I thought ...

However, with an input on any channel, there was no response - no signal
presence light, no peak light, no dancing segments in the display. A few
voltage measurements determined that the PSU was not outputting any +15v
to the analogue input board, so back out it came. 4R7 sm resistor in the
feed to the +15v regulator transistor was open. The transistor itself
was also short circuit, and the zener. After replacing these, the +15v
was back, but still no response from the analogue board, so I guess that
the opamps on there had probably been ****ted as the psu failed. This
brought me to the point of serious debate as to whether it was worth
carrying on. This issue was promptly resolved by a slip of the meter
probe when the phone rang and startled me. The +48v phantom feed goes up
to the analogue board, along with + / - 15v and +5v. Guess which pin the
48v is right next to ...? Yep, the 5v, and the very next place it goes
is the hard drive. "Squeal - squeal - squeal " goes the replacement HDD,
as the mouse that runs it inside, is electrocuted ...

With a sigh, I reached for the pot of screws, and put it all back
together. Some faults are just not intended to be repaired. To be
honest, I had reservations about this right from the start, but when
work is quiet, and you are presented with what looks like a
straightforward problem, it's easy to get sucked in. Note to myself.
Trust your instincts, boy ... :-(

Arfa

I'm sure we've all experienced the same situation. Multiple times. One
in recent past for me was a Yaesu FT847 HF/VHF/UHF amateur transceiver.
Suffered a proximity lightning strike down the antenna. The diplexer
taking the single downlead combo vertical VHF/UHF antenna splitting it
to a UHF N and SO239 on the set took most of the charge. However the
set had no VHF RX. I spent what seemed like weeks trying to repair all
the damaged components. I did manage to get about half of the RX
sensitivity back though before giving up and putting the mess back
together. We ended up sending it back to Yaesu-Vertex where obviously
they could just replace the whole VHF RX innards. ****ed me off to spend
all that time and only get half the receive back. And back then I had
some decent test equipment including a Marconi 2955. I was pretty popular
with the local amateur radio community repair-wise. Just renewed my FCC
Tech ticket. Into year 21 now



--
Live Fast, Die Young and Leave a Pretty Corpse

In article , Jim Yanik
writes

I had a TEK 1700 switcher supply that regulated on the +5V rail,and when
the +5V filter cap's ESR went high,the other rails drove up,for example the
+40 went to +63

Had the same problem with a Compaq DLT7000 drive. The PSU's attempts to
maintain the 5V line with a leaky cap resulted in the 12V line reaching
22V and cooked the drive.

--
Mike Tomlinson

"Mike Tomlinson" wrote in message
...
In article , Jim Yanik
writes

I had a TEK 1700 switcher supply that regulated on the +5V rail,and when
the +5V filter cap's ESR went high,the other rails drove up,for example
the
+40 went to +63

Had the same problem with a Compaq DLT7000 drive. The PSU's attempts to
maintain the 5V line with a leaky cap resulted in the 12V line reaching
22V and cooked the drive.

--
Mike Tomlinson

Yep. Just as you think that you've got the measure of switchers, and the
downstream problems that faults on them can cause, along comes one like this
to slap you back down ...

Still, the rest of the week wasn't actually too bad in terms of number of
items fixed, the repair values of them all, and cash in as a result. And to
get next week off to a good start, yesterday a box of boards from a company
that I do repairs for, turned up out of the blue, so that's a half day's
work for about a day and a half's money, and then today, I picked up enough
repairs from the shops that I do work for, to fill the back of the car, plus
the back seat, plus the front passenger seat, and the foot wells in front of
both. Now all I've gotta do, is unload it all, and book it all in ...
d:~}

Arfa