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Peavey Classic 30 oscillating

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  • Peavey Classic 30 oscillating

    I have Peavey C30 with oscillating problem
    Here is the link
    Peavey C30 oscillating - YouTube

    This oscilating is permanent after turn on the amp. Relatively quiet without anything connected but much louder when I connect guitar cable without guitar. It's same and when I put guitar cable into FX return socket what mined premap section is disconnected (or not?)

  • #2
    normally, cracked soldering connections on the jacks, or the controls. Resolder board.
    Clean all jacks and controls.
    Most of the time, that's all folks.

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    • #3
      No, all connections are right. Yesterday I found the problem is in power transformer. I have been used one headphones amplifier to amplify signal from FX send without power tubes. There were oscillations. The oscillations persist even with C30 turned off with power on/off switch. This oscillations come from the power transformer like induction. Headphone amplifier box was in the chassis of C30 with secondary terminals of the power transformer totally disconnected from the C30 PCB. Same oscillations I was hear in the headphones until I disconnect power mains cable from the wall. This oscillations are almost gone and amp is usable quiet when I power on C30 via transformer with ratio 1:1 (220V/220V). Any idea how to solve this? Some filter modification on the primary side of the power transformer or power line filter can help?
      Last edited by proff; 01-19-2014, 08:11 AM.

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      • #4
        AC line filter doesn't work and doesn't solve this problem. The only thing that works in this case is connection of the amplifier main cable to the voltage regulator 220V/220V without grounding ! In that case C30 looks more powerful and much louder.

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        • #5
          I seem to recall that I have seen this on some Peavey amps that rely on chassis connections to complete an earth connection. Might be worth trying to unscrew the jack connectors or pot screws clean the metal a little, or moved the star washer round and see if there is any improvement.

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          • #6
            I checked all jumpers for more than 3 times. Re solder all points on the pcb but problem is still there. I can't understand why this amp have 3 different ground points because when the pcb is fitted on the chassis all different ground points are on the same potential with input, fx send/return and ext speaker/remote jacks....

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            • #7
              Those different ground circuits may wind up at the same potential, but the arrangement keeps control over WHERE ground currents flow, and so they reduce hum.
              Education is what you're left with after you have forgotten what you have learned.

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              • #8
                Originally posted by proff View Post
                I checked all jumpers for more than 3 times. Re solder all points on the pcb but problem is still there. I can't understand why this amp have 3 different ground points because when the pcb is fitted on the chassis all different ground points are on the same potential with input, fx send/return and ext speaker/remote jacks....
                Few more ideas to try to isolate the issue.

                Bit of a scattergun approach but worth a quick try is to probe the amp with a chopstick/wooden spoon to see if a particular part of the chassis/pcb responds to vibration when you tap the chopstick on the components/PCB/chassis etc. Particularly near the jack sockets but all along the PCB, large components like capacitors. By the way I am assuming that you know what you are doing regarding safety here. If not confident please do not attempt.

                More methodilcally
                Do any of the controls effect the level of the oscillation e.g. does volume, mid, treble etc. increase/decrease the sound of the oscillation?

                If you put a patch cable linking the FX send and return does that effect it.

                Mike

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                • #9
                  Ok, but that can't solve this problem I hate this pcb !!! Worst pcb seen ever... This situation is really annoying me so pls give me some idea where I can find the source of this problem
                  If all solder points are right and no broken jumpers what causes the problem?

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                  • #10
                    This oscillations are controlled from volume potentiometers on both channels. When I increase volume the oscillations are louder. When I put just cable in FX returrn socket oscillations are still there but without changeable level. When I take a signal from FX send socket to another amplifier is the same. Oscillations are tone stack sensitive so maybe the problem is some in preamp part of this amp or oscillations come from the rectifiers when they are always there in all situations ???!!! (only preamp tubes, only power tubes...)
                    I didn't try to link FX send/return but I'll do that
                    Last edited by proff; 01-20-2014, 09:41 AM.

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                    • #11
                      Problem solved.
                      Two wires (6,7 connected to ground) in the ribbon cable from middle pcb to ext speaker/foot switch control sockets were broken on the pcb side.
                      I swap ribbon cable with wires and now everything is fine.

                      Tnx to all of you for your suggestions

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                      • #12
                        It's a great feeling when you get it working again. Well done.

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                        • #13
                          I have a another one problem with my C30. There is some clock noise like a clock in the chorus or delay effect. Tic-tic-tic... one tick per second. It's not a loud noise but I don't like it. Any suggestion pls. This noise is without anything connected to the amp
                          Last edited by proff; 03-31-2015, 08:23 PM.

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                          • #14
                            Is your cell phone sitting on the amp?

                            Does the amp do this somewhere else, like a friend's house? It could be noise in the electrical environment.
                            Education is what you're left with after you have forgotten what you have learned.

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                            • #15
                              Could be a close by electrical fence. They pulse one every second. These can sometimes travel quite far.

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