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Thanks Joe, this one was working fine until I messed up and allowed the meter to touch the grounding bar. I'm thinking a new bias transistor might fix the low bias issue. Here are the pics. You can see in the picture the bias pot is turned all the way clockwise, and it is running at .32 bias...

Alright, the WOPL 400 is up and running nicely, but for one small issue. The left channel bias is at .34. The trim pot works, but won't take it any higher. The right channel has a full range of adjustment. I searched the site, but did not find an example of this low bias. Any ideas? It has the...

Do you eat any of your 40 cows?

Back at it. Took it back to the recommended startup procedure. I was able to determine the back plane is fine. Pretty much isolated the issue to the right channel of the control board. Further testing to follow.

indeed. I was surprised.

I replaced the transformer in my wopl pl400 today. Powered up great. Well, almost great. The left channel is working perfect, the right channel bias and output test points are showing 82V on the bias test points as well as the output test point. I think I'll take a break and tackle that next. I...

I'm not one to ask for help, follow the recommendations, fix the problem, and never report back. after trying and replacing just about everything, I still kept coming up with the left channel working perfectly, and the right channel with 0 bias. So I threw it off the back of a truck... Nah, I...

I use Dielectric grease on motorcycles...

Awesomeville!

mr joe, am I in the que for those boards I ordered? :)

Did you replace the the 10 Ohm resistors -YES What is the voltage on R25 - AROUND 7V, however, tough to get a measurement given i have about 4 seconds to work with. If you lift on leg of D12, does R25 still get hot? - N0 LONGER GETS HOT Remove the yellow wire on the control board for the Right...

Thank you sirs! I'll get going on those tests and get back.

I replaced Q7 and Q10, the bias remains at .550 and r 25 is still getting hot as a pistol.

I swapped all the transistors from side to side, and there is no change. Also took bias readings from both 10ohm resistors on the right channel. The one closest to the end of the cabinet reads .550, the one on the other side reads .07. Neither respond to adjustment of the pot.

OK, R41 checks out at .21...

here is the impacted R25. Thanks for the help!

Well, I'm back, did you miss me? hahaha. So here is where I am at. The PL400 with PL14 board. I have now replaced the transistors with new 96's, (bottom row are 410's). My DC offset on both channels is almost undetectable. The Bias on the left channel is set at .360, however the right channel...

Good going Gene. Did you go with white? PS I think I have this pl400 tamed after going through and replacing all the 10W resistors, and the .001 capacitor. I went ahead and installed the WA output relay, and the DBT has quit lighting up. My final challenge is the right channel has .350 bias...

3V bridge rectifier? Smarty pants! LOL

The part by part testing will resume this evening while watching NCAA basketball. For now, it's 60 degrees outside, and I have a 71 Norton Commando that needs some road time.