baronep

New Member
I have a Pioneer Elite VSX-49 (just 49, not TX or TXi) which I have had for several years. All of a sudden I started getting a cracking out of a single channel. Here are the symptoms ...

1. The cracking is only one in one channel
2. The cracking is independent of any control on the front panel & input source
3. The crackling occurs even when the volume is turned all the way down
4. The crackling usually is delayed from turning on the amplifier. It takes anywhere from 2 to 10 minutes before the crackling starts.

I have tried pressing on the circuit board with the rubber end of a pencil to try and tease out a correlation (thinking that a bad solder joint may be the problem) but to no avail.

Does anyone have any idea of what it may be and/or some tests which could prove insightful?
 
Random crackling noises in an old amp usually point to the differential pair transistors going bad, but I repaired 2 amps recently with that same problem and the guilty parts were small signal transistors at the preamp board, before that differential pair. I replaced all in both channels and the differential pair too. If some transistors failed the other are in the same condition. .

A freeze spray will confirm that, freezing the bad transistors will start to do more noise.

Try to clean all the switches and controls, and then I'd replace the transistors.

Replacing the differential pair includes re adjust dc offset. You need a matched pair of transistors for this application. Not for the preamp.

If you have "pre out" connectors you could isolate the problem disconnecting the jumper. If the noise persist, point to the differential pair. If it stops, it's generated at the preamp.
 
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