Off the topic- what to do solid state stereo

[9 volts]

Oh no. my old harmon karmon solid state stereo amp has suddenly got a buzz (loud) when I turn it on. Volume does nothing to alter it. To me it sounds like maybe ac on the speaker line in the final stage of the circuit. (maybe a leaky cap?)I was thinking of measuring for ac on the speaker line with a multimeter using a dummy load. Does this sound like I'm on the right track? I know it's off the topic but I know there is alot people on the forum with alot of wisdom. Thanks

[sed]

If you want to measure, I think you should measure for DC on the speaker line.

[9 volts]

whoops, thats the one (not thinking), a leaky coupling capacitor maybe, loss ground connection......I've built some valve amps and am trying to apply that knowledge.  Thanks again

[Mark Hammer]

Chances are pretty good that the big power-supply caps have their best years behind them.

[petemoore]

  Thinking of replacing all caps deemed "Possibly Wierd", starting with filter caps and testing from there...on these varied 'filled with other guts" chassis units:
  Sounds like my ONKYO, making occasional PoP starting last week.
  Before that it'd take like 1 minute to 'slow start' occasionally.
  The POP comes through but only once in a while.
  My 2006 CCI Re-Issue has waterfall tone accompanying the amplifications...I've replaced the speaker, OT, PT, Tubes...everything expect the resistors, hopefully they haven't figured out a way to mess resistors up.
  For the ONKYO, it's super nice, all kinda fancy preamp inputs, slow start [no-pop turn on], big, loud, sweet sounding...useless for me, I'm not subjecting my speakers to the 'unload' tone of cap-pop.
  The VoX...yea, I replaced all else, why stop at the junko capacitros, maybe build a new amp out of the rest of the 'stamp built' style chassis innards.
  TV needs new caps too.
 

[JDoyle]

I agree with Mark - it's almost certainly a power supply cap failure. If you are going to replace one, I'd replace both (one for each polarity, and there may be more than one, though the chance of that is low). Make sure the voltage rating is equal to or great than (preferable, but gets costly quick) that of the original caps and I would highly recommend increasing the value as well. Though don't go too crazy as the higher the value, the higher the surge currents, which will stress the diodes in the bridge and the transformer, possibly beyond their ability to handle such currents (2x-3x the original value is the max I would use).

Good luck!

Regards,

Jay Doyle

[9 volts]

Thanks everyone. I'll start with the filtering caps (power) and take it from there (this weekend). I've downloaded a schem of the harmon kardon so fingers crossed I'll get it sorted out. Thanks again

[9 volts]

Well... so far....not so good. The amp has a duel power supply. (four big caps- two per side) one power supply per channel. The tests I've done indicate that
1) Right channel has the problem
2) Measuring the voltage (bipolar) indicates about 44+- on both power supplies. Won't this indicate that the caps are ok? I've disconnected the preamp and the noise is still on the right channel.
As to what to look for next..........
Thanks again