A-1020 Amplifier heat

4seatPilot

"Broker"
I'm repairing an A-1020 for someone, and now that I've got it working, I notice that it puts out some crazy heat. Particularly the 8 big grey resistors near the middle of the board... It's obvious that they are expected to get somewhat warm, as they are mounted well off the board and vent holes are found in the board underneath them.

But how hot is too hot? They got over 70 deg C... and that wasn't in Class A. Things really got warm in Class A - with the outputs and main heat-sink also rising over 70 deg C.

Should I be looking to find a way to reduce the temp of these resistors? Or perhaps put in parts that may dissipate the heat better without getting so hot?
 
ya they do get really warm. I would just not even bother with using it in class A. If you give it enough ventilation it should be fine, but you could add a fan if you wanted.
 
This model is very similar to the A-1000. In this model you there are pots to adjust bias and dc offset. The manual for this is in the ak database, the A-1020 could be in there too.
 
Can you change the bias?

This model is very similar to the A-1000. In this model you there are pots to adjust bias and dc offset. The manual for this is in the ak database, the A-1020 could be in there too.

I have a service manual (I just printed it) and it would appear that idle current can be adjusted. I'll try that... but I'd really like to do something about those resistors - change them to something I could heat-sink or something.
 
I've determined that there is room above the heatsink to mount a couple fans - just have to figure out how to supply them with power. I think that's going to be the best solution - I still can't believe the heat even with the cover off - it must be pretty toasty with it on.
 
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