PL700 series 1 “Tim” repair

AngrySailor

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#1
Hmm... I guess “Tim” is acceptable as he’s destined for sub woofer duty, the “muscle”...

Anyways, I’m tearing into this today, fails DBT with no rail fuses. Outputs don’t seem to show any shorts with my mm. I guess I’ll dig in the power supply end of things.
 

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AngrySailor

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#3
Changed rectifier with the 25a NTE I had. Passed DBT with rail fuses in. Dc offset high with 330mV and 200mV, bias 380 left and 590mV right. Have to stop and help Trever with his daughters car for a few hours now.
 

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AngrySailor

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#5
There are 4 pots to adjust offset on that board....
Yes and the two standing vertically off the board are for bias? I have the manual but haven’t read it yet and also won’t mess with things till I have. Making a ravioli casserole rn listening to Linda
 

laatsch55

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#8
That wasn't my intention al all, I was in complete agreement on you using it. Typing on my phone is a PITA...
 

AngrySailor

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#11
Ok so I’ve read over the manual. I’ve checked bias and can’t get enough on the left channel. The pot has almost no effect. Left bias is 39 mV, right I was able to adjust to 356mV.

R20/R29 seem to be getting hotter on the left than right also. Dc offset is a mess. I can’t seem to get it any better than it was. I can set it With the volume pots up or down but I can’t balance it.
 

AngrySailor

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#13
I can get <50mv with the volume pot up or down, then change the volume pot and it’s anywhere from 500mv to 1v +/- depending on where you set the minimum (volume pot up or down).

It was set around +500mV and would go -500mV with the volume pot down I believe.
 

laatsch55

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#14
And you are using both sets of 5K adjustable pots as in the service manual.
 

AngrySailor

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#15
And you are using both sets of 5K adjustable pots as in the service manual.
Yes, volume pot down, use r7 I think? Then volume pot up, use r17. I’d have to look at the manual again and I’m not infront of the amp rn.
 

AngrySailor

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#19
I would need more, even if all the ones in Linda are ok, I would need 6 more.
 
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