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Onkyo M-508. A couple of questions for the experts

Well, I checked the suggested areas and could not get consistent readings, so the amp is all boxed up and on its way to BK Precision Audio to fix my mistakes. Silly me, I though replacing the electrolytic caps would be a simple job.. as Clint Eastwood once said "a man has got to know his limitations" !

 
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The old M-508 is up and running fine. Minor problems caused by my "old guy eyes" not seeing a couple things. BK audio says:

"I redid the output caps solder pads, then I found a bridged solder joint from the R channel + rail to ground. It fired up then, but still no bias in the R channel. After some investigation I found one leg of Q426 was not quite reaching the solder joint. Bias is back and it's working good now"
 
skinnypuppy said:
Yay awesome!!! It’s always the little details that will bite you.
Click to expand...

I feel a lot better about my upcoming recap of my M-506RS that I got from my brother-- it works fine right now, but the caps are almost 40 years old and should be replaced before they go bad and take out other parts. I have all new caps & outputs for it, I'm just waiting on the four big 22,000uF filter caps to come in (due in from Mouser in in late October). The 506RS is a lot easier to work on than the 508...

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Got the M-508 back yesterday, running cool and even and sounding sweeter than she has in years (new capacitors and outputs will do that for you!)
 
I have been running the 508 for 6-8 hours a day to "break in" the new capacitors using a set of Dynaco A25's... it's amazing how much better it sounds now than it did before the recap, the bass is now deep, strong and smooth where before it was severely lacking and boomy.. the old Dynaco's are marvelous once again.
 
I made a cooling fan unit for the M-508 today: I used four 2 3/4" fans and an 82 degree (F) thermostat right above the warmest spot in the interior. The fans are centered over the heat sinks above the output transistors, they should keep the big filter caps.at a reasonable temperature for long life.

I have the Parasound stuff driving my Infinity RS4b speakers, while the Onkyo stuff is running the Dynaco A-25s

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