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Thread: Help With Tascam M-512

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    Help With Tascam M-512

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    Hello everyone, long time reader first time poster.

    I have used the search function but haven't found this problem before.

    I was doing some recording with my band on the weekend, I have the M512 recording onto a Tascam 38. Everything was going great until,,,,, set everything up for a vocal overdub, hit record and there was no sound. Looked up at the board and all the overload LED's were on all 12 channels even though I was only using one mic input and four tape inputs.
    Turned the desk off for about an hour, turned back on, was still lit up. Turned of again, unplugged everything, waited an hour, turned back on, still all overload LED's stay on. I also noticed that when I press the solo or PFL that light doesn,t come on.

    What has happened!!!!

    Aaron

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    i suspect that one of the op-amps supply rails is toasted... is it fused maybe... sweetbeats put up a schemo for the supply awhile back... check it out... iirc the first opamps are run from an +/-18V ... most likely a voltage regulator...
    37.8% of all statistics are made up on the spot...

    hey give a guy some room... people are trying to evolve here... for crying out loud...

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    dementedchord,

    I was relieved to see you respond!

    The schematics I put up were all M-520 based tho', and the PSU is external on the M-520 and internal on the M-512...

    azza, do you have the manual for your M-512? If not I can scan and post schematics for whatever you need.

    Yeah, there are +/-18V and +/-15V supply rails and I'm sure you are right, dementedchord that the 18V rail supplies those opamps.

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    Quote Originally Posted by sweetbeats View Post
    dementedchord,

    I was relieved to see you respond!

    The schematics I put up were all M-520 based tho', and the PSU is external on the M-520 and internal on the M-512...

    azza, do you have the manual for your M-512? If not I can scan and post schematics for whatever you need.

    Yeah, there are +/-18V and +/-15V supply rails and I'm sure you are right, dementedchord that the 18V rail supplies those opamps.

    Just from memory the +-18 volt rails drive the output opamps so as to get full balanced headroom. All the internal opamps and the peak circuit are on the +-15 volt rails. (nice feature which allows a reduced number of higher cost opamps for the outputs....)

    I vote for a failed supply rail.

    -=Ethan
    No if only I had a 520 .....
    In Sunny Vancouver ..... (Washington)

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    Yep...yer right, Ethan. Your post triggered my memory of a post you submitted in my M-520 thread. You had already done that research.

    The 18V rails are indeed for the output stage, and the 15V are for the internals. Thanks for redirecting that.

    Can't help you with the whole M-520, Ethan, but I'll give you a channel card to mod and keep if you show me what you do to it...

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    Hi, thanks for the responses. I was lucky enough to get the original manual when I bought it. I had a look at last night, but I'll check out the power supply.

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    my bad... i pictured it as an external... figured the 512 was the samw frame just short loaded... and couldnt remember... but i thought the first stage op-amps were the special ones... that's where i woulda put them....lol... i would think the extra swing wouldn't help in a driver stage... usually they are about current handling...
    37.8% of all statistics are made up on the spot...

    hey give a guy some room... people are trying to evolve here... for crying out loud...

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    Yeah...dunno.

    Ethan might/would likely have more to say on that, but the M-500 mixer's outputs are all unbalanced, except for an independent -10 to +4 or +8 balance amp/convertor...8 channel. Its accessible on the back. Just 8 RCA's in and 8 XLR's out and that's all it does. It is not connected internally to anything so you can patch any of the multitude of outputs to it to suit whatever the needs are and maybe that's part of the choice in the 18V rail on the output side...? Speaking outside my scope of knowledge on that...blah-blah.

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    ALL GOOD!!!!!!!!!!

    Stopped of at Dick Smiths on the way home and bought 2 new 15V +/- regulators. Just put them in and everything is back to normal.

    2 new regs-$2.40

    getting back to sweet, sweet analog recording- PRICELESS!!!

    Thanks for the help, you guys are legends.

    Now I have to fix my DBX 128. Has the same problem with the overload staying on. Back to Dick Smiths with another $2.40

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