Adjustable inductors on the Onkyo M508?

87turbot

New Member
I recently picked up an Onkyo M508 that had low garbled output from one channel. Unfotunately I read the DC Offset sticky after I messed things up. I was attempting to adjust the idle current and adjusted the L401,402 "coils" instead of the bias pots. They look like little silver silver boxes with black plastic adj. screws on the left side of the power caps. The amp is now in protection mode and does not "wake up". Does anyone know what these adj. coils do and how to get them back to where they should be. If they need to be replaced how do I determine electrical values for new parts? They are listed in the service manual as NCH 4145. Any thoughts or suggestions would be much appreciated.
 

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quick look at the manual and no mention of correct setting ..
i see they are maybe something to do with the servo .. that's only a wild guess though .
hopefully someone else can work out how to get them set correctly .
 
Looks like an odd feedback mechanism to me...I'd imagine that they'd be adjusted for minimum distortion, thus requiring a signal generator, scope, and distortion analyzer. But even grossly misadjusted I can't imagine that they'd cause any seriously objectionable results.

If you've tweaked them a little, try to put them back where you found 'em. If you tweaked them a lot, I'd either put them somewhere near mid-travel, listen to the amp with the coils adjusted at different positions and set 'em where it seems to sound best (if possible), or get the amp to someone with the right equipment and let them take a whack at it.
 
Adjust the value of the coils. Might be you will get the results. Firstly set them into the low value and then increase slowly. You can check the value of these coils using QLR meter if you are looking for the replacement.

Leiterplattenbestückung
 
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