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Thread: TASCAM 688 - group 1 not working

  1. #1
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    TASCAM 688 - group 1 not working

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    Hello everyone, after reading this great forum for quite a while now, it is finally tome for my first post!

    I've bought a Tascam 688 in good condition a week ago on eBay. The seller described it as fully working and proved it with pictures.

    The thing arrived and it does work, except one thing: group 1 is dead. I can neither record from channel 1 to tape nor can I do a mixdown in stereo using the groups 1/2, as only group 2 works, meaning only the right channel of a stereo mixdown.
    If I connect a mic to input 1 and crank the gain up, the peak LED lights, but the VU meter doesn't show anything.

    The thing is, on the eBay pictures, it is clearly visible that it DID work before the seller packed and shipped it.
    So my first guess was that perhaps a plug or something might have become loose during transport. I opened up the machine and reseated/checked every single plug on every board, took me quite a while. Result: no change.

    Now to my question to the 688 pros: does anybody know where it would make sense to search for the problem? Where do the parts in which the routing/switching occurs actually sit?
    Is this a known problem?

    I don't think it can be much, as it worked before shipping. But where to search?

    Thanks in advance for your help!


  2. #2
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    Dec 2013
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    I'm not familier with this specific model, and i'm not entirely sure of how the assignment section functions, but if you have already took apart the machine, get a good print of the schematics, mark the path for group one, and trace this path component after component, using a multimeter. if you got a short at one point, it might contribute to the problem.

  3. #3
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    Apr 2008
    Pacific Northwest, USA
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    @IronWine : the issue with the 688 and 644, all of the buss assigning is handled via complex hard-contact switches...difficult to suss out.

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