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Re: [korg_mono-poly] Re: Mono/Poly doesn't turn on. (Transformer gets really hot)

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  • Alan Dicker
    Cool.  Thanks Florain ... From: Florian Anwander Subject: Re: [korg_mono-poly] Re: Mono/Poly doesn t turn on. (Transformer gets
    Message 1 of 11 , Dec 2, 2009
      Cool.  Thanks Florain

      --- On Wed, 2/12/09, Florian Anwander <fanwander@...> wrote:

      From: Florian Anwander <fanwander@...>
      Subject: Re: [korg_mono-poly] Re: Mono/Poly doesn't turn on. (Transformer gets really hot)
      To: korg_mono-poly@yahoogroups.com
      Date: Wednesday, 2 December, 2009, 10:11

       
      Alan Dicker schrieb:
      >
      >
      > It could maybe be a Op Amp on that is leaking some timer data in to the
      > signel path. Haven't get scimatics or anything in front of me now

      http://fa.utfs. org/diy/korg_ monopoly/ index.html

      > but could be worth checking the outputs on any Op Amp assoctiated with the Arp.
      There are two connections from/to the arpeggiator (which is +5V
      circuitry) to the OpAmp-World (which is +/-15V circuitry): The
      arpeggiator resets the MG1.
      MG1 feeds the Arpeggio Trigger in and the Arpeggio-Switche reset the MG1.
      Since the signal at the osci is described like an cyclic enabled adress
      line, I think the second option should be the suspected one. It might be
      worth to interrupt this connection. It is the wire from LFO-Board
      connector 6 pin 10 to uP-board connector 23 pin 10.

      Btw: this is a modification I'd recommend anyway, if you do not want to
      reset the arp-Clock with every new chord, that you play.

      Florian

      >
      > --- On *Wed, 2/12/09, plus_321 /<plus_321@yahoo. com>/* wrote:
      >
      >
      > From: plus_321 <plus_321@yahoo. com>
      > Subject: [korg_mono-poly] Re: Mono/Poly doesn't turn on.
      > (Transformer gets really hot)
      > To: korg_mono-poly@ yahoogroups. com
      > Date: Wednesday, 2 December, 2009, 8:23
      >
      >
      >
      >
      > I tried to use an oscilloscope today to check the power rails. I
      > check them on the 356 board, but the seemed fine and I could see any
      > significant fluctuations.
      >
      > I realize that when I unplug the VCA out connector or power input on
      > the VCF board then the noise becomes much louder. So I was able to
      > put the scope on the output and see what it looks like. It appears
      > to be a constant frequency pulse wave with a small cycle length,
      > like 5-10%. The noise doesn't go through the filter so it isn't
      > oscillator bleed and it doesn't track the keyboard. The only thing
      > that really affects it is moving the arp switches.
      >
      > I've found the noise goes away completely if I unplug the arp
      > connector from the 356 board, but if I unplug the same cable from
      > the other end, the noise remains, but is reduced in volume. I
      > checked the cable and it seems good.
      >
      > So I am thinking that either there is something wrong with my 356
      > board that is causing this noise or perhaps their is an issue with
      > the cable routing (perhaps maybe it shouldn't be bundled with a
      > power cable or something).
      >
      > Thanks,
      > Chase
      >
      >
      >
      >
      >


    • Alain
      Just a short (late) reply to tell everyone that the transfo used in most MP4 is running quite hot after a an hour or more of use. It is the result of Korg
      Message 2 of 11 , Feb 8, 2010
        Just a short (late) reply to tell everyone that the transfo used in most MP4 is running quite hot after a an hour or more of use. It is the result of Korg putting a 1.2 amp tranfo in a synth that consumes... 1.2 amps! So that part is working in the proximity of its maximum tolerance, and thus dissipates about 30 watts of heat. But that transfo is of high quality and should be able to handle that kind of heat easily. So I wouldn't worry about that. But no part is infallible and it could still fail.

        Alain.


        --- In korg_mono-poly@yahoogroups.com, "plus_321" <plus_321@...> wrote:
        >
        > Hello.
        >
        > Just a few moments ago I was playing some music and all of a sudden my mono/poly stopped working. I tried to flip the switch and nothing happens; no lights or sound. (I didn't see or smell smoke)
        >
        > I opened it up and the fuses are all fine, but the transformer was so hot that I couldn't keep my finger on it for more than a moment (even now, 15 minutes later it is still very warm).
        > I used the service manual and checked on board 356 for voltages and none of them registered(5, 15, or -15).
        >
        > I'm not sure what to do now. I'm guessing the transformer died, but how can I know for sure? What would cause the transformer to just go out like that? If it is the transformer, does anyone here have a spare or know where to find one?
        >
        > Thanks,
        > Chase
        >
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