electrolytic audio cap exploded w/ pics - GK 1001RB amp

[Todd H.]

Greetings,

First, for the .components folks, I'd like help IDing the manufacturer
of an electrolytic cap -- what company has a logo that appears to be a
horizontal oval with large block "E" inside with a script "m" (or
could be something else?) next to it. Here's a photo that includes
a sample -- the cap on the left is the same manufacturer as the one
that is...well, no longer with us:
http://www.triplethreatband.com/todd/

For the .repair folks, I'd like to tap the experience of the group as
to possible "why's?" on a recent capacitor explosion in a 2 year old
audio power amplifier (more precisely a bass guitar amp/preamp made by
Gallien Kruger - GK 1001RB).The amplifier is just a little over 2
years old.

The cap that exploded was an electrolytic in the audio path, in the
power amplifier--pretty much in the middle of the power amp circuit
just ahead of a transistor that was tied into the heatsink. Here's a
photo:
http://www.triplethreatband.com/todd/

I don't have the schematic with me, but it was C23 if perchance there
are schematics-armed GK techs lurking about here. I can't recall the
capacitance value...but it was a 50V rated cap. The supply rails of
this power amplifier are +/- 90V if memory serves me.

Thanks in advance for any insights here...the amp is in the hands of
an experienced tech and I'll know more soon, but I'm just curious
about how common such a thing is, and the usual reasons for such a
failure.

Best Regards,
--
Todd H.
http://www.toddh.net/

 

[michael turner]

On Tue, 17 Feb 2004 10:59:29 -0600, Todd H. wrote:

Greetings,

First, for the .components folks, I'd like help IDing the manufacturer
of an electrolytic cap -- what company has a logo that appears to be a
horizontal oval with large block "E" inside with a script "m" (or
could be something else?) next to it. Here's a photo that includes
a sample -- the cap on the left is the same manufacturer as the one
that is...well, no longer with us:
http://www.triplethreatband.com/todd/

For the .repair folks, I'd like to tap the experience of the group as
to possible "why's?" on a recent capacitor explosion in a 2 year old
audio power amplifier (more precisely a bass guitar amp/preamp made by
Gallien Kruger - GK 1001RB).The amplifier is just a little over 2
years old.

The cap that exploded was an electrolytic in the audio path, in the
power amplifier--pretty much in the middle of the power amp circuit
just ahead of a transistor that was tied into the heatsink. Here's a
photo:
http://www.triplethreatband.com/todd/

I don't have the schematic with me, but it was C23 if perchance there
are schematics-armed GK techs lurking about here. I can't recall the
capacitance value...but it was a 50V rated cap. The supply rails of
this power amplifier are +/- 90V if memory serves me.

Thanks in advance for any insights here...the amp is in the hands of
an experienced tech and I'll know more soon, but I'm just curious
about how common such a thing is, and the usual reasons for such a
failure.

This is about dud el. caps. on PC mainboards:
http://www.pcstats.com/articleview.cfm?articleID=195
Possibly related to your exploding caps problem.

--
Michael Turner
Email (ROT13)
zvxr.gheare1963@ivetva.arg

 

[Patch]

"Todd H." <bmiawmb@toddh.net> wrote in message
news:m0eksty74e.fsf@rcn.com...

Greetings,

First, for the .components folks, I'd like help IDing the manufacturer
of an electrolytic cap -- what company has a logo that appears to be a
horizontal oval with large block "E" inside with a script "m" (or
could be something else?) next to it. Here's a photo that includes
a sample -- the cap on the left is the same manufacturer as the one
that is...well, no longer with us:
http://www.triplethreatband.com/todd/

For the .repair folks, I'd like to tap the experience of the group as
to possible "why's?" on a recent capacitor explosion in a 2 year old
audio power amplifier (more precisely a bass guitar amp/preamp made by
Gallien Kruger - GK 1001RB).The amplifier is just a little over 2
years old.

The cap that exploded was an electrolytic in the audio path, in the
power amplifier--pretty much in the middle of the power amp circuit
just ahead of a transistor that was tied into the heatsink. Here's a
photo:
http://www.triplethreatband.com/todd/

I don't have the schematic with me, but it was C23 if perchance there
are schematics-armed GK techs lurking about here. I can't recall the
capacitance value...but it was a 50V rated cap. The supply rails of
this power amplifier are +/- 90V if memory serves me.

Thanks in advance for any insights here...the amp is in the hands of
an experienced tech and I'll know more soon, but I'm just curious
about how common such a thing is, and the usual reasons for such a
failure.

Best Regards,
--
Todd H.
http://www.toddh.net/

The 2 most common causes for exploding electrolytics are supplied voltage
exceeding the rated voltage & hooking one up with the wrong polarity.

 

[Tim Wescott]

I know of four reasons that an electrolytic (aluminum or tantalum) will
explode: reverse voltage on the cap, either at the moment of failure or
before; overvoltage on the cap, at the moment or before; the cap dries out,
or a faulty cap.

My only direct experiences with reverse voltage were both very dramatic (and
entertaining, in the case of the student who, when I asked him if he'd
hooked the cap up with the correct polarity said "polarity?"). Both of
these events resulted in the capacitors directly entering trans-dimensional
space warps, with no pieces but the leads to be found. I've heard that you
can cause latent damage to a cap with low-voltage polarity reversals that
will show up later as capacitors blowing up.

Overvoltage on the cap does the same things (from the outside-the-case view)
as reverse voltage. I haven't made this experament.

Aluminum electrolytics are "wet" -- they actually have a water-based
electrolytic solution that makes one of the electrodes. If this
electrolytic dries out the capacitor fails, either open or short. If it
fails short it explodes. This is why aluminum electrlytics have altitude
ratings -- without atmospheric pressure to help the seal they leak and dry
out. I have been told (don't know the truth of it) that bending the leads
of the cap right at the rubber seal will create a leak and cause the cap to
dry out, as will elevated temperatures.

"Todd H." <bmiawmb@toddh.net> wrote in message
news:m0eksty74e.fsf@rcn.com...

Greetings,

First, for the .components folks, I'd like help IDing the manufacturer
of an electrolytic cap -- what company has a logo that appears to be a
horizontal oval with large block "E" inside with a script "m" (or
could be something else?) next to it. Here's a photo that includes
a sample -- the cap on the left is the same manufacturer as the one
that is...well, no longer with us:
http://www.triplethreatband.com/todd/

For the .repair folks, I'd like to tap the experience of the group as
to possible "why's?" on a recent capacitor explosion in a 2 year old
audio power amplifier (more precisely a bass guitar amp/preamp made by
Gallien Kruger - GK 1001RB).The amplifier is just a little over 2
years old.

The cap that exploded was an electrolytic in the audio path, in the
power amplifier--pretty much in the middle of the power amp circuit
just ahead of a transistor that was tied into the heatsink. Here's a
photo:
http://www.triplethreatband.com/todd/

I don't have the schematic with me, but it was C23 if perchance there
are schematics-armed GK techs lurking about here. I can't recall the
capacitance value...but it was a 50V rated cap. The supply rails of
this power amplifier are +/- 90V if memory serves me.

Thanks in advance for any insights here...the amp is in the hands of
an experienced tech and I'll know more soon, but I'm just curious
about how common such a thing is, and the usual reasons for such a
failure.

Best Regards,
--
Todd H.
http://www.toddh.net/

 

[Todd H.]

"Patch" <bob_acord@hotmail.com> writes:

The 2 most common causes for exploding electrolytics are supplied
voltage exceeding the rated voltage & hooking one up with the wrong
polarity.

Given that the amp worked for 2 years without so much as a glitch,
reversed polarity is probably something I can safely rule out.

Overvoltage is certainly a possibility..say if a transistor shorted
somewhere. It's a 50V cap, and the supply rails are + and - 90V.

But... does anyone know -- could a defective cap short itself, and the
resulting current from the short cause it to vaporize its electrolyte
and blow its pressure vent? And then the next time it's powered up,
explode? I think I witnessed this progression (in one powre cycle I
saw the smoke, and curiosity didn't prevent me from trying it one more
time to see if the speaker protection circuitry was being activated or
not--that's when I witnessed the sound and light show of the cap
exploding).

So...this warning: "If the capacitor vent used in an electrical product is
triggered and the gas is visible, immediately unplug the power cord or
turn off the main switch to the equipment." from
http://www.elna.co.jp/en/ct/c314_inde.htm is something I witnessed
first hand!

Best Regards,
--
Todd H.
http://www.toddh.net/

 

[Walter Harley]

"Todd H." <bmiawmb@toddh.net> wrote in message
news:m0eksty74e.fsf@rcn.com...

The cap that exploded was an electrolytic in the audio path, in the
power amplifier--pretty much in the middle of the power amp circuit
just ahead of a transistor that was tied into the heatsink. Here's a
photo:

If it's in the audio path, it's possible that it doesn't have DC bias on
it - that is, it's being called to function as a nonpolarized cap. That can
be bad. I've heard it's more a problem with tantalums than Al's. Maybe GK
figured they could get away with a polarized Al?

If another component value drifted, or an opamp drifted, a DC-coupled stage
could develop an offset voltage which was in the wrong direction from the
unfortunately-not-nonpolarized cap. That might account for why it took 2
years to blow.

Just guesses.

 

[Peter de Vroomen]

Last year a lot of capacitors on computer mainboards started to fail. There
was talk of trade-secrets having been stolen, but incorrect, resulting in
some manufacturers creating batches of bad quality capacitors.

This is a mainboard of mine:
http://home.wanadoo.nl/p.vroomen/gfx/miscpics/ecs_condensators.jpg. The
mainboard was about 2 years old when it failed a year ago. Most of the
capacitors have bulged, and a few had leaked. The result was that one of the
power-mosfets developed a hole, through which it's smoke was released. And
components don't work anymore when they lost their smoke :+).
http://home.wanadoo.nl/p.vroomen/gfx/miscpics/ecs_mosfet.jpg. If you look
closely at the picture, you'll also see that the small transistor in the
middle-left of the picture (Q21) has developed a pimple.

So it's most likely down to bad quality capacitors.

In this case, the mainboard is a cheap ECS K7S5A, and it's not worth
repairing it.

PeterV

 

[FoxyRick]

On Wed, 18 Feb 2004 10:30:02 +0100, "Peter de Vroomen"
<peterv@ditweghaluh.jaytown.com> wrote:

Last year a lot of capacitors on computer mainboards started to fail. There
was talk of trade-secrets having been stolen, but incorrect, resulting in
some manufacturers creating batches of bad quality capacitors.

This is a mainboard of mine:
http://home.wanadoo.nl/p.vroomen/gfx/miscpics/ecs_condensators.jpg. The
mainboard was about 2 years old when it failed a year ago. Most of the
capacitors have bulged, and a few had leaked. The result was that one of the
power-mosfets developed a hole, through which it's smoke was released. And
components don't work anymore when they lost their smoke :+).
http://home.wanadoo.nl/p.vroomen/gfx/miscpics/ecs_mosfet.jpg. If you look
closely at the picture, you'll also see that the small transistor in the
middle-left of the picture (Q21) has developed a pimple.

So it's most likely down to bad quality capacitors.

In this case, the mainboard is a cheap ECS K7S5A, and it's not worth
repairing it.

PeterV

Hey, I (well, my wife) had one of those MB's do exactly the same

thing, about six months after a much more expensive Abit board did it.
It explained the continued data corruption I had been seeing on the
Abit PC for 6 months. I repaired the Abit (getting capacitors small
enough to fit was the problem). It still works perfectly now!

I didn't bother with the ECS either, just told my wife we needed to
spend yet more money on PC stuff ;-). The board around the MOSFET was
badly burned.

Cheers,
FoxyRick.

 

[John]

Abit MB same here, lost 2 PSU's and a RAM stick.

"FoxyRick" <KilledBySpam.com> wrote in message
news:gdt630tnet6g7mbrou8s5lofo3p8u2hmfo@4ax.com...

On Wed, 18 Feb 2004 10:30:02 +0100, "Peter de Vroomen"
peterv@ditweghaluh.jaytown.com> wrote:

Last year a lot of capacitors on computer mainboards started to fail.
There
was talk of trade-secrets having been stolen, but incorrect, resulting in
some manufacturers creating batches of bad quality capacitors.

This is a mainboard of mine:
http://home.wanadoo.nl/p.vroomen/gfx/miscpics/ecs_condensators.jpg. The
mainboard was about 2 years old when it failed a year ago. Most of the
capacitors have bulged, and a few had leaked. The result was that one of
the
power-mosfets developed a hole, through which it's smoke was released.
And
components don't work anymore when they lost their smoke :+).
http://home.wanadoo.nl/p.vroomen/gfx/miscpics/ecs_mosfet.jpg. If you look
closely at the picture, you'll also see that the small transistor in the
middle-left of the picture (Q21) has developed a pimple.

So it's most likely down to bad quality capacitors.

In this case, the mainboard is a cheap ECS K7S5A, and it's not worth
repairing it.

PeterV

Hey, I (well, my wife) had one of those MB's do exactly the same
thing, about six months after a much more expensive Abit board did it.
It explained the continued data corruption I had been seeing on the
Abit PC for 6 months. I repaired the Abit (getting capacitors small
enough to fit was the problem). It still works perfectly now!

I didn't bother with the ECS either, just told my wife we needed to
spend yet more money on PC stuff ;-). The board around the MOSFET was
badly burned.

Cheers,
FoxyRick.

 

It looks like there would be less than 20vdc across this cap under normal
conditions. It probably was not a cap failure initially - but more likely
the cap reacting to some other component failure. I would guess a failure of
Q17 or Q18. If one of these went "shorted" you would likely get full supply
at one end of this cap - severely over-voltaging it. Unfortunately when one
transistor fails there can be a pretty severe domino effect. Perhaps one or
more of your outputs shorted and this is part of the colateral damage.
Hopefully this is not the case with your amp but I would get ready for not
so good news if I was you. . The rest of your board is pretty good looking
but your tech will be smart to check every single silicon component on that
board not to mention emitter resistors & low voltage supplies in the
vicinity before powering up. This is not an easy amp to service because of a
top mounted heatsink and the way it all goes together. If you have more than
a few shorted outputs & etc, you would probably be best served by replacing
the entire output board as it is probably cheaper to do that than pay the
parts & labor required to troubleshoot & fix. Good luck - hope my guesses
are wrong!
Todd

please visit our website:
www.amprepair.com

 

[Michael]

"Todd H." wrote:

Given that the amp worked for 2 years without so much as a glitch,
reversed polarity is probably something I can safely rule out.
(snip)

No! Never assume such a thing. It's pretty easy to check.
In my work life I used 18 identical black boxes to verify I/O data
throughput of mainframe computers. Each black box had its logic on a
dozen or so cards that plugged into a backplane. After about ten years
of using these test vehicles, they began failing one by one. My
technician finally traced the problem to two electrolytic caps. that had
been installed backwards when the cards were manufactured ..... 12 years
before.