Sony F570ES audio amplifier cracks

Hi ser!

My audio amplifier cracks, recently especially on 's' or 'sh' sounds, as if the signal was overdriven. Also there are cracks when the volume knob is adjusted and the left outputs channel mutes occasionally, and it comes back when I turn the volume higher.

Here are some pics:

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I found 2 overheated resistors (1 watt rating, IMO). When I vacuumed the dust some of the lacquer broke away, exposing the resistor material helix, which looks quite ok. The small PCB in picture 4 (dscn7183) fits into the row of holes to the right of the overheated resistors in picture 1 (dscn7174). It contains the volume adjust resistor block.

What do you suggest?

Replace the 2 overheated resistors? Should I use 4 instead of each, two parallel pairs in series, to avoid overheating? Unless I find a

4 W type, if there is such a thing. I don't see any potentiometers nearby so I guess it wouldn't matter much if the value of the new resistors differed within the rated tolerance.

Replace the volume resistor block? I'm afraid that might be hard to get.

Or might the fault be somewhere else?

Thank you, Bernhard

Reply to
Bernhard Kuemel
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Do you think I might successfully test the resistor block by connecting it to the line-in (or mic) input of my sound card in series with a 1.5 V battery and see if there are any discontinuities/cracks when I adjust the resistors?

Bernhard

Reply to
Bernhard Kuemel

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