I am repairing a Definitive Technology BP-7004 Super Tower's power supply / amplifier that makes a buzzing noise when it is cold. After it warms up, the buzzing slowly fades away. I've attached an image (link below) identifying four surface mount capacitors. I'd like some further insight in determining their values from the markings: 10 25G 405

I've looked online and found various resources, but none seem to be definitive as each manufacturer seems to have their own marking schemes. Is there a way to determine who manufactured these capacitors?

The capacitor with the scratch (lower left) is the bad one. I "tested" it by applying a low temp soldering iron to the top to heat it up a little. The buzzing would go away, I was then able to cool the cap with an inverted can of "dusting air", once the cap was cooled, the buzz returned. Testing each cap with a soldering iron is time consuming, so I was able to narrow down the bad spot by first directing a heat gun at different parts of the board.

I've seen several postings by other BP-7004 owners looking for a method to solve this buzz. Hopefully these capacitors are the bad point on all of the boards that buzz. Replacing a dollar worth of components is much better than the $140 for a new board from the manufacturer.

Photo of Capacitors

--Edit with new information -- I have a replacement board from the manufacturer and the "new" capacitors are marked a little differently. The new caps read "h1., 10, 25V". I'm hoping that means 10 micro farad and 25 Volts, I have no idea about "h1." though. Photo of new capacitors

  • \$\begingroup\$ why not open up one and measure the capacitance value? through the LCR meter or by RC time constant? \$\endgroup\$ – Umar Jan 13 '17 at 20:27
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    \$\begingroup\$ 10µF, 25V. In the past, there had been markings where the letter indicates the voltage but 25V seems right for that capacitance and size. \$\endgroup\$ – Janka Jan 13 '17 at 20:38
  • \$\begingroup\$ By the way: you should do something against the glue paste on the right boiling on the heatsink. \$\endgroup\$ – Janka Jan 13 '17 at 20:40
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    \$\begingroup\$ Never had such caps which had the voltage first. \$\endgroup\$ – Janka Jan 13 '17 at 20:49
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    \$\begingroup\$ Another hint is the capacitance values usually follow the E-series while the voltage values usually do not. So 25µF is an odd value, should be either 22µF or 24µF or 27µF. \$\endgroup\$ – Janka Jan 13 '17 at 21:00

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