Newly assemble pl14 rev G bias trimmers do not work correctly

George S. said:
Ivan, you have a early 400 that was built with a quasi complementary point to point wired back wall, then the output transistors where selected and installed specifically for that quasi complementary back wall.
If you've not modified the back wall by rebuilding it full comp and installed the different output transistor configuration, then you need to build the control board quasi complementary to match it.
Also check your fuses for correct type and value. Some of these amps have had automotive fuses from the old Pontiac behind the barn or straight pieces of heavy copper wire.
Ask any question and we'll try to help. Nice job on the board!
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Ok thank you, I will go back and rebuild it Quasi comp. I appreciate the help.
 
CrazyIvan said:
I will try to get back to this tomorrow, thank you all for your help. I will keep you posted.
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Good Luck! Also make sure you change some diodes also,,,,,, you still need power to the RT board Pins 11 and 12
 
Looks like your amp has blown before, you have at least 3 different date codes on the output transistors. You may want to check and make sure none are open or shorted
 
CrazyIvan said:
Hello, I recently added the DC protection, then new power caps from WO. I just assembled the pl14 rev G board. Started on a DBT no issues. went to adjust bias and my DMM readings are -.019 DC on both sides. Bias trimmers turned full CCW to start. Turning CW has no effect on the DMM. I am using board test points and white and red speaker outputs as test points. If I read between white and black or white and red I get .003 VDC. It doesn't seem normal to not get any bias adjustment. Any help is appreciated.
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Did this PL 400 II work before the Upgrade?
 
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Ivan, also, as WOPL Sniffer said " please check the polarity of the caps on the DCP board".
Here's, a photo. Note the negative marks on the cap and the positive marking on the board.
 

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If you did power these caps installed backwards do not use them as that can possibly unwind the cap and open up all sorts of issues
 
CrazyIvan said:
yes it worked before the upgrade. it worked after the DC protection upgrade, it worked after the cap upgrade, the pl14 board was the next upgrade.
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That's a good way to do it , One step at a time , just fix the board and let us know what you changed , as a double check. Make sure you fix
the DOP board "Cap" like WOPL Sniffer pointed out and look at George pic. Also make sure you save all the Components you take out so if you do decide to got Full-c, you will have saved all the parts. Good luck
 
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Quasi appears to be working now. redid board as required. Anyone know how decent Watts is to deal with? I bought the DCP board prebuilt. In trying to switch the cap, it took the trace out of the board when removing.
 

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CrazyIvan said:
Quasi appears to be working now. redid board as required. Anyone know how decent Watts is to deal with? I bought the DCP board prebuilt. In trying to switch the cap, it took the trace out of the board when removing.
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He will make it right, he stands behind his boards
 
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