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Thread: TASCAM M-600 Meter Bridge VU lights turn off / on

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    TASCAM M-600 Meter Bridge VU lights turn off / on

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    Hi there

    I have recently restored a TASCAM M-600. All is running pretty well but an unusual issue has just popped up.

    I noticed that the lights in the VUs (all 16 PGM and the Master VUs) occasionally go dim for about 1/2 a second then come back on. The audio is not affected during this time, i.e. it does not drop out - just the VU lights go off/on very briefly. I dont know if the actual VU meters stop or its just the lights cause it is very random and only occasionally so I really only notice it out the corner of my eye then they are back again. So I think its juts the lights but it may be the actual meters stop working as well. I will try to clarify but I can, but as I said it is only occasionally and at random, so hard to actually check.


    I am not sure were to start looking to troubleshoot this issue? I assume on the EXT METER PCB ASSY? I believe from the circuit diagrams that is were the power for the VUs comes in?

    I though maybe the meter bridge wiring but the fact they all go off/on at the same time makes me think its something that affects them all from one source (ie the meter PCB)

    Any advice would be super...


    EDIT - It is only the lights that go out - the VU meters still work and audio is not disrupted - if that helps point to a place to start looking


    UPDATE - I seem to have resolved the issue (for now at least). I changed the capacitors in the 8v circuit on the PSU and also notice the fan was not working - the PSU was getting VERY hot. I replaced the fan and it now runs pretty cool and I have not had the VUs dim since. Not sure if it was the caps or the fan or both but it seems to have fixed the issue for now!

    Thanks
    Last edited by pelagos; 09-11-2020 at 17:01. Reason: update

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    The VU meter lamps run off of A/C. A/C line voltage sagging, like when a refrigerator, Air conditioner unit turns on?

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    Quote Originally Posted by wkrbee View Post
    The VU meter lamps run off of A/C. A/C line voltage sagging, like when a refrigerator, Air conditioner unit turns on?

    Thanks for the info..

    I don't think that is effecting it as the circuit that my studio is on is seperate to the rest of the house.


    From the PSU is it the 8v power that feeds the VU's? There seems to be +/- 16V, Phantom and 8V supplied from the PSU? Im not really all over the power supply thing! I did change the caps in the 8v section of the PSU to see if that will make a difference. Have not tested since changed but will report back if it helps.

    I did notice the other day that it seemed to get worse (i.e. VU's dimming more) when I had a lot of channels working (i.e. mixing 18 channels at once) as opposed to just 1 or 2 channels. Not sure if this was just coincidence, or the more 'power drain' on the system the worse it got??

    thanks

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    Most meters lamps are run off their own secondary winding. I would suspect a connection issue. Have any lamps been changed and the wrong one put in? Automotive .25A lamps are entirely wrong for meter lamps.
    Lamps are commonly wired in parallel. At 55mA a lamp you can add up what they will need. JKL DA513 is what I use most of the time.
    Best regards,
    Skywave Tape Deck Repair, Chicago area

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