KA-8100 operating temperature - how cool/warm/hot does yours run?

Seeking observations from anyone who has experience with a KA-8100. I am working on one presently and am curious.

What types of operating temperatures have you observed with your KA-8100? Were bias settings for the amp known when you made your observations regarding operating temperature?

Thanks in advance :)



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I have a dialed in 8100 I could run some temps on with my infrared thermometer. What/where specifically is concerning you?
 
It is not so much a concern, as it is something I am curious about. Hopefully we can collect a few data points in this thread and see whether there is any trend.

If you could tell me please, your impression of what is going on at the main heatsinks as compared to other amps you have experience with. No measurements necessary.
 
IIMO, it's a warm running amp. Besides the 2 regulators on the front board, there are a couple of resistors that run hot on the main board. And the TO-3 outputs also seem to run warm even at idle. Bias on mine is spot on and I've never stressed the amp enough to see much change in operating temp. Ventilation seems adequate....
 
Ok @roger2 I ran the amp for a couple of hours at a low background volume. Feeling all the areas of the top of the case It's no warmer than I'd expect it to be. Warmest spot was right of center, slightly closer to the rear. The left side where the transformer is definitely cooler. I've regreased the T0-3s on this one so that should be noted. It certainly runs cooler than the 9600 does and I'd say equivalent if only slightly warmer than the 7100. Adding some low profile heatsinks to the regulators, couldn't hurt. Hope this is of some help.
 
thanks hopjohn. yes very helpful we have two data points now, woohoo! just a simple poll...

interesting that the side nearer to the transformers in your amp is cooler. would have thought the opposite


for future posters, my main area of curiosity is the main heatsinks and TO-3's, and whether the bias settings are known to be factory spec (14mv) or not
 
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Mine - all original with bias adjusted to 14mv - runs warmest on the left heatsink, considerably warmer than the right.
 
Thanks gort69.

The main outputs/heatsinks of the 8100 I have here run unusually cool. Bias is at 14mV and outputs have new mica and thermal compound. The left heatsink is warmer than the right side. But I think that is because of the heat coming off of the transformers adding to the heat generated by the outputs.

The regulator transistors on the control board of my sample do run hot. I would think that all KA-8100s would be the same.

@hopjohn I don't understand what you meant when you said: "Adding some low profile heatsinks to the regulators..." . How could this be done? The two main regulator transistors are already mounted on either side of a U-shaped heatsink. How could you add another heatsink?
 
@roger2 At the time of writing I was probably thinking the regulators were located on the main board as the 7100, but I'm assuming they are on the control board instead. In that case, just a simple cleaning and replacement of the thermal compound would be all that was needed.

I have only dug into a few of these so I don't have them devoted to memory as I do some other KA models.

hop
 
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If you caught a glimpse of that last post, ooops!!! wrong unit. you this read wrong
 
Mine as always run warm. Got it brand new too. Was my daily driver for
yearsssssssss. The regulators, on the control board always run hot.
Just re-capped the whole thing, re-greased all regulators and TO-3's.
Adjusted Offset and Bias, still run's warm. I even used it as a pre-amp
for a while and the outputs still run warm...
Great amp!, has been bulletproof for me for 38 years!. The pre-amp section
is awesome, sounds better then the power amp section, to me.
 
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