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Amp started buzzing - cap replacement?

post #1 of 3
Thread Starter 

I have a pair of active monitors that are 10 years old.  Until recently, they had been working perfectly.  Suddenly they both started buzzing.  I've eliminated the electrical in the home or nearby interference by trying a variety of locations within the house.  This particular set of monitors has a single (2ch) amp in the right speaker that drives both speakers (speaker cable connects them).  I'm thinking a capacitor in the amp's power supply died causing the sudden buzzing.  I plan to open it up and look for any obvious signs of distress (bulging caps, etc.).  Is there anything else that I might look at to debug the problem if the caps aren't the problem?

 

I'm comfortable working with power supplies; I've replaced caps in a few computer power supplies and a few Tivos.

post #2 of 3
Quote:
Originally Posted by Greg_R View Post

I'm thinking a capacitor in the amp's power supply died causing the sudden buzzing.  I plan to open it up and look for any obvious signs of distress (bulging caps, etc.).

 

That's a good thought, something common to both channels. It could be something as simple as a failed solder joint though, due to thermal stress.

 

The starting point with any fault finding exercise is to use your eyes. Just inspect the assembly for anything that looks wrong. Burnt, loose... 

 

w

post #3 of 3

Yeah or maybe corrosion ate away a ground wire. Or the circuit board itself...

 

As wakibaki said, the first thing to do it a visual inspection. The problem may be obvious once you open the enclosure. Check for disconnected or broken wires.

 

If everything seems alright, here's what I'd do: Turn the thing on while it's open, and use a non-conductive stick to push or press down on components. If you're lucky, you should find a broken joint that way.

 

10 years is considerable. It's probable that the capacitors are drying up. Even if you find the problem to be something else, I'd change them anyways. But then I try to find myself reasons to solder stuff, especially when I'm bored...

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