M3500 console meter issue

Discussion in 'TASCAM DIY Repairs and Mods' started by brendanh, Jun 22, 2014.

  1. brendanh

    brendanh New Member

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    Anyone have any ideas what might be causing the meter in channel 13, and also the Peak led on the VU meter to be lit up even when there is no signal going into the console, see attached pic..
    I tried plugging a drum mic into channel 13 and the meter maxed out even with channel input gain turned all the way down and pad switch pressed in. I haven't yet had a chance to test if the audio is ok through this channel. But both meters remain the same even when there is no mic lead plugged in.

    Any ideas or help anyone can offer is appreciated.

    Attached Files:

  2. witzendoz

    witzendoz Active Member

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    From:
    Fremantle, Western Australia
    Gear:
    M3700 MX2424 MSR16S
    Need a bit more info,

    When you plugged the mic in did the channel have noise as well as the pegged meter?
    Need to know if audio is getting through.
    Alan.
  3. brendanh

    brendanh New Member

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    Hi Alan,

    At this point I can't say if there is any noise or not. I bought the console 2nd hand and only just powered it up for the first time. I have channels 1-8 routed into my interface using the direct outs on those channels on the console and the audio through those seems fine. However I'm yet to test the audio through the affected channel by hooking it up to the interface, will do so in the next few days and let you know what I find.
  4. brendanh

    brendanh New Member

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    Hi Alan,

    I've routed the the audio into the channel and out through the direct out into my interface, and it seems to work fine, I can't hear any unexpected noise and seems to be plenty of the audio I want.

    The peak led on the vu meter seems to flicker on and off intermittently bust mostly just stays on, even when there is no signal being input into the console
  5. witzendoz

    witzendoz Active Member

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    From:
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    Gear:
    M3700 MX2424 MSR16S
    Sounds lie it could be a loose/dirty connection on an internal ribbon cable?

    Alan
  6. wkrbee

    wkrbee Active Member

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    Most likely a op-amp in the meter circuit failed,slamming the output to the meter to the power rail
  7. brendanh

    brendanh New Member

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    Thanks mate, any ideas on tracing the issue to find the faulty part?.. Sorry my electronics knowledge is fairly limited.
  8. wkrbee

    wkrbee Active Member

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    A slammed opamp would cause the meter to peak and then fall back on power up.
  9. brendanh

    brendanh New Member

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    Yeah I'm not real sure how to diagnose or find the faulty op amp, so I've just been using that channel for talkback