Enzo, I believe you are on to something with the volume control board on channel A. With the four pin molex plug disconnected to the volume board the voltage to U2 pin 4 does in fact recover to the -15vdc.
Just to confirm I moved my good driver card over to channel A again and with the connector plugged in I was only getting the same low -11.18vdc with that board also. Removed the plug and back to -15vdc.
Investigating the volume control card seems to be the next step. I didn't think I needed to go there because before I had the component failure on the driver board while testing with full power the channel worked.
What is the trick for removing the DDT LED bulb thats mounted to the chassis but connected to the board? I don't want to break it when removing the board.
Thank you again for all your help with this repair.
CS 800 C Series driver board issue
Re: CS 800 C Series driver board issue
I figured out the DDT LED removal. It is just a compression ring on a sleeve, pried off the ring and pushed out the bulb. I removed both Channel A & B volume control boards to compare values. No differences found.
I reinstalled the boards and now I am back to getting -11vdc on driver board with or without the volume board connected. For the heck of it I went ahead and replaced CR 6 zener diode again, no change. Still the -11vdc on the IC.
FYI, the schematic correctly calls out volume control board as a 99309032 and that is what this amp has installed, but the layout drawing of the board attached to the print has components mounted in a different orientation. But I laid the boards side by side and compared each component one by one. Everything measured almost exactly the same.
How does the song go, "One step forward and two steps back".
I reinstalled the boards and now I am back to getting -11vdc on driver board with or without the volume board connected. For the heck of it I went ahead and replaced CR 6 zener diode again, no change. Still the -11vdc on the IC.
FYI, the schematic correctly calls out volume control board as a 99309032 and that is what this amp has installed, but the layout drawing of the board attached to the print has components mounted in a different orientation. But I laid the boards side by side and compared each component one by one. Everything measured almost exactly the same.
How does the song go, "One step forward and two steps back".
Re: CS 800 C Series driver board issue
Um...
Well I WAS going to say one of the ICs on the volume board was likely bad, but if you now get 11v even with that volume board out of circuit, I am not sure what you have.
Well I WAS going to say one of the ICs on the volume board was likely bad, but if you now get 11v even with that volume board out of circuit, I am not sure what you have.
Re: CS 800 C Series driver board issue
Okay Enzo, thanks so much for trying to help me with this. I did confirm once again that the A channel would work by installing the good driver board to that side. If replacement driver boards were available I would have bought many weeks ago. Perhaps I will find someone selling a old amp for parts and revisit this repair in the future.
This forum and I have been so very fortunate to have a guy like you who takes the time working thru problems with strangers. I am aware that you have posted extensively on this site and other boards as well. I have probably read every Peavey CS800 post that had your input, there are many. I am not a religious man, but you sir should qualify for sainthood for you patience and time spent helping others doing something you ought to be paid for.
Thank you, Enzo!
This forum and I have been so very fortunate to have a guy like you who takes the time working thru problems with strangers. I am aware that you have posted extensively on this site and other boards as well. I have probably read every Peavey CS800 post that had your input, there are many. I am not a religious man, but you sir should qualify for sainthood for you patience and time spent helping others doing something you ought to be paid for.
Thank you, Enzo!