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Old 16th October 2012, 02:42 PM   #1
bongo is offline bongo  United States
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Default Forte 1a - little buzzy, runnin' hot.

Greetings sportsfans.

I just started noticing that, on power-up, my Forte 1a is doing a little bit of 60hz buzzing, not over the outputs, but rather the physical case. Presuming its a slightly annoyed transformer? It seems like it goes away after it gets warm. (NB- it's about 21 years old... I should buy it a drink?)

Secondly- I know the rule of thumb is that it's not running 'too hot' if you can still put your hands on the heat sinks... well, I can't. Of course, I could just be wimpy... what with my delicate scientist typing hands and all.

I used my little thermal-measurin'-gun and see that it's running around 54°C/130°F, same on both sides, about 10°F warmer toward the 'front' of the heatsink (toward the faceplate) than the rear.

Thoughts? Everything OK here, nothing to see?
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Old 16th October 2012, 02:55 PM   #2
Zen Mod is offline Zen Mod  Serbia
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well , buzzing as buzzing

some screw tightening or loosing (is it EI or toroid ? ) can maybe sort the thing

regarding temp - put some risers below legs , be sure that airflow isn't disturbed in any way

if that is not helping , then you need to rebias it
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Old 16th October 2012, 03:56 PM   #3
bongo is offline bongo  United States
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Indeed- I'll experiment with varying amounts of torque. Love torque.
I will elevate it a little bit above its current 'height' above the shelf it's in. It's open on all sides, so it's not a matter of circulation I don't think.

I recall seing biasing instructions on here at some point? I'm usually a +5VDC hack, but this is such a beautifully elegant/simple design it seems like I should be able to handle the work without hurting myself, or, more importantly, the amp
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