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Troubleshooting crackly channel

D

DoktaDave

New Member
Hi. I need some help diagnosing a problem. I have a Kenwood KA-3500, which has developed a problem with one of the channels crackling. The crackle doesn't start immediately when the amp is turned on, and takes at least a minute to get going. The channel still plays, but does seem to be down on volume when the crackle is loud, although I'm not certain of that. It isn't affected by moving any of the controls on the amp, and it still happens through different speakers. I've tried the second output of the amp, and again, the crackle comes through the left channel. I've had the unit apart, but can't find any dry/loose looking solder connections.
Any ideas on what this could be and how to fix it?
 
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It is probably a noisy transistor. Buy a can of freeze spray. Connect a set of speakers you don't care about. Spray a small amount of coolant on each of the small transistors in the power amp section one by one. The one that makes the noise worse or better is the bad one.
 
My restored KA-3500 has developed a similar issue in at least one channel, it is back with a fellow AKer who did the restoration work on it to diagnose. It had been suggested that this could be a power supply diode issue rather than transistors. Anyone with other advice or experience on this amp/issue? Other than the crackle, which after the amp warms up occurs every couple of minutes, the amp works great...
 
J English said:
My restored KA-3500 has developed a similar issue in at least one channel, it is back with a fellow AKer who did the restoration work on it to diagnose. It had been suggested that this could be a power supply diode issue rather than transistors. Anyone with other advice or experience on this amp/issue? Other than the crackle, which after the amp warms up occurs every couple of minutes, the amp works great...
Click to expand...
It's transistors. It uses 2SC458 transistors. They become noisy. There may be others.
 
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