Today, I go to check it out to see what's going on. I turn down the master volume, turn it on, I hear the usual power up capacitor charging hum, and when the protection circuitry turns off, instead of the usual quiet, I hear strange humming/noise/hiss after a loud, unusual turn-on thump. I power it off and power it on again to the same humming of power up, and a very big thump hits the speakers when the protection circuitry clicks off, I hear the same hissing/humming loud noise so I power down immediately...and watch a little puff of smoke emerges from the front panel. Ah she-ite. Well, we know it's not my guitar jack anymore--we have a confirmed amp head problem. I unplug the speakers, and endeavor to see if the protection circuitry is being engaged at all. I power the unloaded amp up again...power-on hum of capacitors charging up, protection circuit clicks off after the usual 5 seconds, and SNAP CRACKLE POP I hear from inside the head along with a sparking lighting show visible from the cooling holes. I power down immediately, and unplug the unit from the wall. I check warranty status--and am treated with the news that the warranty expired 2 months ago. But in every cloud there's a silver lining--this means I get to dissect! I even have schematics. 8-)
Well, here's what's left of the capacitor C23's innards--notice the
brown paper like goop blown all over on the neighboring components,
and the two little plates that are bent over....kinda neat. Here's
how to find the capacitor: At the top of the picture you see the side
of the large heatsink. On the left of this photo, you see a large
black intact capacitor, following that row of components to the right,
you see 3 little resistors running vertically, then a bigger resistor,
and then, a brown intact capacitor, and then a bunch of papery lookin
brown capacitor guts covering several components--I believe that's
what's known as "electrolytic paper" which separates the anode and
cathode of aluminum electrolytic capacitors. In nearly the dead
center of the picture you see a silver metallic lookin thingee that
is laying vertically... it appears to have 2 holes on it. I believe that's one
of the two contact plates of the blown capacitor. The one visible is
bent over (upward in picture) from it's black round base. The base of
the capacitor below that contact in the photo, just above the white
blasted out circular item in the middle of the picture (which is
actually a trim pot to set the bias in the poweramp). Now, the white
stuff that appears to extend north of the metallic contact plate of
the capacitor is actually a
very shiny reflective gray foil like material--if my recent reading on
aluminum electrolytic capacitors is accurate, this would be one of
the aluminum foil electrodes of the capacitor. I _think_ the papery
crap we see might be exploded electrolytic paper. What I can't
figure out is where the electrolyte itself is, unless I'm wrong about
how much electrolyte fluid is actually in such capacitors.
Below is what was left of the capacitor
shell that got launched upwards and was found rolling around the
inside of the amp after the little lightning show I saw:
But I'll be damned--the rest of the board (below) looks okay. Hopefully the
capacitor blowing and the very limited time the unit was under power
kept the failure confined to one component. I hope so since this
thing is just 2 months out of factory warranty, and I'm not interested
in a multi-hundred dollar repair bill.
My take? Capacitors blow...this isn't yet an affront to GK quality, but more so the quality of their capacitor manufacturer. Unless of course, some other issue caused an overvoltage condition to cause this capacitor failure. Time will tell and I'll keep you posted.
--Todd H 15Feb 2004