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Problem with +/- 15 supply to op amps

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  • Problem with +/- 15 supply to op amps

    My X100B has a 15 volt +/- supply that works the op amps and the 4049.I am getting +10 where I should be getting -15.I have replaced all components and its still getting +10.When I hook up the foot switch the switching functions work like its getting a ground it needs from the switch connection but it still has the 10 volts.It has a bridge rectifier from the transformer and at the diodes and caps after it the -15 is there.Checked the tranny and it is fine.It seems there may be a 0 earth ground getting into the - 15 rail but after tracing it many times I still cant find where.I use this amp a LOT.I really need it up and running so any help would be greatly appreciated.

    Schematic is here

  • #2
    I wonder if D11 and/or D14 are in backwards. That would tend to make the negative rail not be negative.

    Hope this helps!


    • #3
      Try pulling the op-amps out and see if the voltage comes back. If one is shorted it will do that. If it gets shorted to ground it will read zero not 10 volts and it will show 0 all the way back to the rectifier. Something is loading it down and you may have to go 1 op-amp at a time until you find the culprit. Usually there is also either a 15volt zener or a voltage regulator TO-220 package type for regulation.


      • #4
        I moved some things around and now I have a low volume all the way up.The effects boost is switching the channels but the channel switch is working.I put the new transistors in by the diagram of the circuit board but I will double check if my replacements have the same pin out.THe D's are all in the right way.

        It only comes on when I have the switch plugged in the back.I also soldered a jumper to a pot ground and when I connect it to the switch jack ground that works so I have a bad ground some where.You can hear both channels at once so basically my update is:

        Bad Ground,Low Power,and Both Channels on at once.

        I havent done much with logic ICs so I am learning about this switching system as I go.It seems like a whole lot of crap just to switch channels.

        I also posted the wrong schematic,mine is the previous revision HERE

        Its almost the same,except mine has 6L6s


        • #5
          Got a little further.There was a bad op amp.They were all new so I didnt expect something so obvious as a new part being bad.Now I have both channels at a good volume but its both channels at once.A4 (op amp for loop and reverb) pulls the signal way down but it may be a bad part as well,going after some new ones today.Im just glad my output transformer is good.This thing took a good jolt,which is what hurt it in the first place.My logic may be bad too making the channels go at once so I getting a new one and trying that.


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