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Adjusting settings on Kenwood L-07M amp

saabracer23

saabracer23

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Subscriber
So I replaced a couple of the output transistors in the L-07Ms and now its time to adjust all of the settings. In the service manual it states to put the negative probe of my DMM on the number 23 post of the power supply board and then to ground the positive probe and it should measure -63Vdc. I measure and I actually get a +63.3 Vdc. Is it the same as measuring DC offset and it does not matter if its positive or negative or does it matter in this case? I'm fairly certain there isn't enough movement in the potentiometer to swing from -63V to +63V. I'm going to hold off on any other adjustments until I get a response I guess. Thanks!

Dan
 
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The only reason they ask that you ground the positive is because in the service manual they show the adjustment being made with an old analog VOM. Their leads have to be swapped for negative voltages. A modern digital meter measures negative voltages just fine. Kenwood is also misleading novice techs by labeling the adjustment graphic in the manual '-63V'. Their meter can't measure negative voltages without swapping the leads around, so the -63V is disingenuous. Yes, that's the actual voltage we want there. No, you won't measure -63V if you ground the positive meter terminal and connect the neg to #23.

Put the negative lead on a good ground and measure #23 again. Got -63V? Or something close to it? Good...make your adjustment and move on.
 
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