Help with Accuphase E-202 Power Supply voltage

[Joe Kraft]

I need to tap in to some Kenwood/Kensonic/Accuphase gurus. I am restoring a very nice Accuphase E202 integrated amplifier and I am having difficulty getting the proper voltage out of my power supply board. (719-0004-00). I have recapped and replaced all heat stressed resistors. I have replaced most of the transistors on this board and tested all the other components and still am getting strange readings. On the collector side of the regulators Q9 and Q10 I am supposed to have 84 and -84 volts respectively. I am getting 13.1v at the collector of Q9 and -12.8v at the collector of Q10. I have circled these test points on the attached schematic. Note: I do have the expected 87v at the test points just upstream from this. I wish Echowars was still active, I know that he is familiar with this board. Also, I know that R27 and R28 are supposed to get hot but they get REAL hot really fast. I have already replaced them with larger wattage 680 ohm wire wound resistors. Thanks so much for all the help.

 

[clinic-audio]

Hello

I have replaced most of the transistors on this board and tested all the other components why did you replace transistors who are working well ??
Why don't you start by the beginning ?
Do you have the right voltages after D1 and D2 ?
If you have the voltages that you have indicated, probably D1 and D2 are dead . This model after some years get this desease
Double check that and come back to us
Replacing overheated resistors is a good idea but doing a recap like many guy did that is silly before to have made the repair

 

[Tala Mink]

Id start by removing all the preamp boards and seeing if that changes anything voltage wise, the low voltages at the collectors of Q9 and Q10 are because they are sourcing too much current through the 680 ohm resistors.

If the voltages still aren't correct the problem should be on the power supply board.

If the voltages correct themselves you can put each preamp board back in one at a time to see which one is causing the problem.

Did the unit work before you started the restoration?

 

[Joe Kraft]

Thanks for the help. First, to answer clinic-audio, I do have normal voltages out of D1 and D2. I have the +/- 55v and the +/-87 volts. I have the 87v right up to before the split to go to R29/30 and R27/28. To answer Tala Mink, I am currently working a 24 hour shift, but as soon as I get home I will certainly give that a try and see if that helps. Can you please explain why you think it is the preamp boards creating this issue? Thanks so much for the help, both of you.

 

[Tala Mink]

The regulated +/-40v only go to the preamplifier boards, I'm honestly not sure that one of them is the problem but since they all socket in its easy to remove them and know for sure.

Also im assuming the power supply functions properly since you already worked on it.

 

[Joe Kraft]

Well, I was optimistic but alas no improvement. I even pulled some preamp boards from a parts machine and swapped them out just in case it required a positive feedback but no. Thanks for the recommendations. I am about to pull the boards out and try them in a different chassis to see if the issue is somewhere in the chassis parts or connections. Thanks again for your help. Cheers.

 

[Joe Kraft]

Well, there is progress. I pulled all of the restored boards out and put them in a different chassis and I got perfect voltage readings. So now I know it is not something in the boards and I just have to really go over the chassis parts and connections very thoroughly.

 

[Joe Kraft]

I found the culprit. A small wire going to the tone board was pinched by a mounting screw and was shorted out. Thanks guys for keeping me focused. Finally can get this beauty off the bench.