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Need help with Allen ADC 2000 - Unwanted sustain/chiff-pop

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  • Need help with Allen ADC 2000 - Unwanted sustain/chiff-pop

    Over the last few years my ADC 2000 started to crackle and volume drop out on one of the two channels, so an electrical engineer friend loaned me some contact cleaner to try on the amplifiers' gain controls. I took both amps out, cleaned the control with the Chemtronics 2000 and the problem seems to be fixed. Now I'm noticing the swell voices seem to have a slight sustain and chiff/pop that increases gradually from mid-keyboard to the lowest C. The great manual does not have this problem. I've taken out all the boards, cleaned the contacts, and replaced them. I've also loosened and tightened all the flathead screws easily accessible in the console to no avail. Any ideas what could be causing these added unwanted "features"? Thnx.

  • #2
    Have you tried reseating all of the EPROM chips? (They are large integrated circuits with glass windows on the tops of the packages, usually with Allen part number stickers covering the windows.) Your problem is often caused by poor contact between the EPROMs and their sockets. The systems-level cause is something amiss in the keying or envelope generator circuitry.

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    • #3
      Don60, thanks for the suggestion. I've reset all the Eproms and no change. I ended up swapping a couple of the "equivalent boards" and when I got to the two TG-6 voice boards, I pulled the Eproms and kept the same voices for each manual. Surprisingly, the chiff/pop/slight distortion moved from the swell to the great. So, if logic prevails, I have a bad TG-6 board. Next, I went to ebay and found a replacement board. However, I received a message from the seller saying upon testing they discovered an issue, so I'm back to square one trying to find a replacement TG-6 ADC/MADC board. Anyone out there know where I can find one? Thanks.

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      • #4
        Originally posted by OldAg View Post
        ...so I'm back to square one trying to find a replacement TG-6 ADC/MADC board. Anyone out there know where I can find one? Thanks.
        OldAg,

        Welcome to the Forum! I hope you continue participating here.

        One other source I'm aware of is Daffer Organs' Electronic Organ Parts. However, they have up to the TG-5 in stock, but alas, no TG-6. So I guess you need to keep a close eye on *Bay, as various people are parting out ADC and MADC organs now. Not sure why. I guess the sum of the parts is worth more than the whole.:'( I feel your pain, as you can see by my signature. I favor the ADC technology.

        Best of luck finding a replacement.

        Michael
        Way too many organs to list, but I do have 5 Allens:
        • MOS-2 Model 505-B / ADC-4300-DK / ADC-5400 / ADC-6000 (Symphony) / ADC-8000DKC
        • Lowrey Heritage (DSO-1)
        • 11 Pump Organs, 1 Pipe Organ & 7 Pianos

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