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Thread: Studer A807 Motor Problem

  1. #11
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  2. #12
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    By substitution method, I tracked the problematic IC was IC17(TL072). I replaced it and the speed problem is solved but something else is causing problem. At times when I press "play", the capstan is not moving. I have to use something to physical turn the shaft and then it moves. Can it be due to lack of lubrication or the capstan drive IC.

    Thanks

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    I think if the drive IC fails, the motor will stop spinning at all, since it's controlling the phases of the motor. I'd be inclined to suspect one of the drive transistors. Especially if this wasn't happening with the other capstan board.
    Interestingly, the manual shows an additional circuit that some machines have, a 'capstan start control' board (1.727.332.00). If present, Q1 on that is responsible for giving the motor an initial push to start it.

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    Yes, it has a small PCB mounted on the capstan board, it has some resistors and 3 transistors on it. I will check the drive transistors and the 3 transistors on the PCB as well.

    Thanks

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    Quote Originally Posted by carlosraj View Post
    Yes, it has a small PCB mounted on the capstan board, it has some resistors and 3 transistors on it. I will check the drive transistors and the 3 transistors on the PCB as well.
    Thanks
    Yeah, if the starter board is fine, but one of the phases had lost a drive transistor, it would likely be operating at half-power - enough to keep it running, but not enough to start. In that scenario there would be a one-in-three chance of it trying to start on the weakened phase...

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    I took out the board again and checked the 3 start board transistors, the drive transistors and the other transistors as well. They were all OK, so I put back the board and tried again. Now the problem is no more there, tried for a few hours, so far so good. I think it was due to some loose connector while putting back the board earlier. I will keep monitoring.

    Thanks

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    Quote Originally Posted by carlosraj View Post
    I took out the board again and checked the 3 start board transistors, the drive transistors and the other transistors as well. They were all OK, so I put back the board and tried again. Now the problem is no more there, tried for a few hours, so far so good. I think it was due to some loose connector while putting back the board earlier. I will keep monitoring.
    Thanks
    Good luck!

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