AMP repair Help- crackle or static noise

[ffury10]

I have a Dual XPE 2700 car amp. It still works and plays. removed from car and bench tested.

When bench tested with power with 1 speaker bridged with no rca or unbalanced input,

There is a crackle or static sound intermittently. It happens periodically every 10 to 20 seconds and last 2 to 5 seconds.

I have narrowed it down to the left channel.

I have opened the case up and see no scorched marks or bad caps etc.

Twisting the gain and frequency switches back and forth reveals no reaction or static response.

I have a digital thermometer and have looked for hot spots.

I find some 2N5401 Transistors running at 55-60 Celsius or 130-140 Fahrenheit?

I find a single 101 thermistor running at 60 Celsius.

What is the normal temperature of internal components?

How hot is to hot?

Any suggestions on what to look for to eliminate crackle???

Any suggestions

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