Soundhaspriority wrote:
"Tiger Luck" wrote in message
...
For the record, the amp is in an Advent 300, which I refuse to let die.

Here's a PDF of the schematics:

http://www.davidreaton.com/PDFs/Adve..._schematic.pdf

The cap that blows is C313. It is a 100mfd 35volt cap It is the filter cap
connecting the negative rail in the lower channel to ground. It is on the
far lower right of the schematic, just above the separate, isolated
schematic of the 15 volt regulator circuit.

The voltage on the negative rail is as it should be. The polarity of the
cap was correct. The corresponding cap in the other channel does not blow.
Both caps have the negative connected to the same source from the power
supply and both have their positives connected to ground. In other words,
the negs of both caps are connected together to the negative rail from the
power supply and both positives are grounded, yet one cap blows and the
other doesn't. The cap blew with a sharp crack and the rubber plug at the
bottom blew out. The cap that blew is not shorted. It still acts like a
cap should when measured with an analog ohm meter. I installed another,
new cap of equal value and it started heating up, so I cut the power.

I'm not a pro tech, but fairly knowledgeable and good at logic and such.

Any insights?

Take a look at the points where the + and - caps are grounded. If that part
of the ground bus is intact, but the bus is broken on the way to the supply
ground, so that it is isolated, that point could float up towards +22 volts,
making the total voltage over the cap that blows 44 volts. Which cap blows
is whichever leaks less, just a matter of chance. So check that ground bus
very carefully for integrity.

Bob Morein
(310) 237-6511


Hi,Bob and thanks

The grounds are intact. By that I mean to say that point in the CB where
electrolytic caps C312 and C313 are grounded is continuous with the ground at the
power supply filter caps. Chassis is the same. All points which are supposed to be
grounded are continuous as read by an ohm meter.


--
Einstein forgot to carry the two