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Pitch bend not working and a few other problems.

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  • eric justin
    Hey Gang I have a Poly 800 first generation mkI that is giving me some problems. The pitch bend doesn t seem to work at all, though VCF/DCO mods(up and down)
    Message 1 of 2 , May 6, 2013
      Hey Gang
      I have a Poly 800 first generation mkI that is giving me some problems. The pitch bend doesn't seem to work at all, though VCF/DCO mods(up and down) work fine. I sprayed some deoxit in the bend range slider but it didn't help. Next, there is a problem with the sequencer. I put the p800 is sequencer enable mode and was able to program a sequence. The start/stop button worked fine in this mode but once I disabled the sequencer and pushed start, nothing happened. The sequencer started up fine when I synced it to my MPC, just wouldn't start with the internal clock. I'm not sure if this is a problem with the start/stop button or something deeper. My suspicion is that something is wrong on the little board that contains the sliders, but I'm not sure where to start looking.

      Eric
    • synth.surfer
      Hi Eric, I just joined the group. I repaired a badly acid damaged Mk1 yesterday, and one of its final issues was the same as you are seeing with the step
      Message 2 of 2 , May 8, 2013
        Hi Eric,

        I just joined the group. I repaired a badly acid damaged Mk1 yesterday, and one of its final issues was the same as you are seeing with the step sequencer. You know that it is reading the start/stop switch correctly from your sequence recording mode. I used a scope on mine and found that the ES5.5 clock on pin 9 of the CPU was missing. Further tracing showed the input on pin 3 of IC28 40H(C)74 was good and varied with the sequence rate slider, and it was not being held in reset. Replacing IC28 (I used a 74LS74) was the cure.

        This does not explain your bend issue, and your bugs may be completely different. If you have access to a scope then you can check the signals through the circuitry.

        Chris

        --- In korgpolyex@yahoogroups.com, "eric justin" <djericjustin@...> wrote:
        >
        > Hey Gang
        > I have a Poly 800 first generation mkI that is giving me some problems. The pitch bend doesn't seem to work at all, though VCF/DCO mods(up and down) work fine. I sprayed some deoxit in the bend range slider but it didn't help. Next, there is a problem with the sequencer. I put the p800 is sequencer enable mode and was able to program a sequence. The start/stop button worked fine in this mode but once I disabled the sequencer and pushed start, nothing happened. The sequencer started up fine when I synced it to my MPC, just wouldn't start with the internal clock. I'm not sure if this is a problem with the start/stop button or something deeper. My suspicion is that something is wrong on the little board that contains the sliders, but I'm not sure where to start looking.
        >
        > Eric
        >
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