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  • C3 fault

    Hi all,

    New member here from the UK. I have been told I should join to hopefully gain some insight into my issue with my C3

    i have a crackling noise that sounds cyclic, the volume which can be modulated by the expression pedal and also normal and soft tab. The scanner sounds fine and the noise does not stop when turning scanner upper and lower tabs to off. So I'm assuming it isn't that. I haven't pulled the back off yet to start fault finding so would welcome any advice to help shorten the fault finding process. My head says the issue lies in the preamp area. Included here is a video I took last week showing the issue.

    Thanks for reading
    Last edited by UKC375; 01-29-2019, 04:58 PM.

  • #2
    The scanner is always in circuit, whether the tabs are on or off - the tabs merely direct signal to the _input_ of the scanner; while the output is always connected.

    Your problem sounds like a typical scanner short.
    Current organs: AV, M-3, A-100
    Current Leslies: 22H, 122, 770

    Comment


    • #3
      I've had a similar symptom in the past. It turned out to be a dirty slipring in the scanner.
      Hammond B3 (55), B3 (70), B3 (72), B2 (51) conversion, A100 (61) chop, A100 (62), A105 (75), Northern BC (39) empty.
      Pile of Leslies of various flavours, Minimoog, ARP Odyssey, MaxiKorg, Hohner D6, Rhodes 54, Rhodes 73, Wurlitzer A200, Wurlitzer A203W

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      • #4
        It sounds like a mechanical noise to me ,can't tell from the video where it's coming from, but if your sure i's the scanner, then disassembly and rebuild, is the only option .

        There is a bobman video on Youtube showing how to do this.

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        • #5
          It's not mechanical, it sounds like an electrical crackle like a spark. In the short term I'm presuming I can put a voltage across the scanner to temporarily clear the dendrites. It's interesting to note the scanner is not disabled in the audio path. I have seen the disassembly video of the scanner, looks quite precarious. But maybe the only option I have to fully clear it.

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          • geoffbrown
            geoffbrown commented
            Editing a comment
            Your there I'm not but that does sound like metal hitting metal

        • #6
          If it comes out the speaker, scanner
          C2 1953, as old as I am and 760 rebuilt, Custom M3 1955, custom HX3, Hohner OAB, Ventilator, Service for friends on A100, B3, BV, M100 and some Leslies

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          • #7
            Yes it's coming out of the Leslie, not noticeable otherwise.

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            • #8
              I don´t know the rpm of the scanner, but it should be same frequency
              C2 1953, as old as I am and 760 rebuilt, Custom M3 1955, custom HX3, Hohner OAB, Ventilator, Service for friends on A100, B3, BV, M100 and some Leslies

              Comment


              • #9
                I had something similar once AFTER rebuilding a scanner, because I had mistakenly gotten the rotor slightly misaligned, it was running a bit too close to the stators (not properly centered between the stator "laminations".
                Current organs: AV, M-3, A-100
                Current Leslies: 22H, 122, 770

                Comment


                • #10
                  to be sure, I would desolder the vibrato input ,I suppose Terminal D, on the AO 28, if the noise is gone, it must be the scanner
                  C2 1953, as old as I am and 760 rebuilt, Custom M3 1955, custom HX3, Hohner OAB, Ventilator, Service for friends on A100, B3, BV, M100 and some Leslies

                  Comment


                  • #11
                    Originally posted by Hoaxel View Post
                    I don´t know the rpm of the scanner, but it should be same frequency
                    412 rpm, about 7 undulations per second.
                    Current organs: AV, M-3, A-100
                    Current Leslies: 22H, 122, 770

                    Comment

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