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Thread: Otari smoking (literally....)

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    Otari smoking (literally....)

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    OK, so on a lark I bought a MX5050BIIB (Ebay...) . Not too expensive. As is, so didn't expect much and figured worst case could use as a parts machine anyway. So, transport doesn't engage at all. It was sort of ff and rew, but not playing at all, and then froze up with just buzzing. Reels were stiff to move by hand even. Finally a pop and puff of smoke from the left reel table. Anyway, suggestions? I am getting a manual with schematics, for the other Otari I have. Figured I'd take it apart and have a look.
    Last edited by Blue Jinn; 02-21-2009 at 12:03.

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    Check for tape that got wound up under the reel table, that maybe got tangled in the shuffle. Just a thought?

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    Check if the reel-tables got pushed in during shipping.
    They shouldn't be stiff and if you tried playmode and reel-motors stuck, the fuse or in worst case motor went dead

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    The tables would spin though in FF and REW. (Altenately, and only on one side, so it seems both motors were engaging, with the opposite very tight.) It almost appears as though the breaking mechanism is locked somehow. Before the buzz/pop/smoke, it would play and then slow down and stop. (This was only holding the tape guides, and not with any tape wound.) Wouldn't budge with some tape threaded. I'll look at the tables though, have another exact model to compare with.

    I'm wondering if it may be a selenoid. Am I correct in guessing that this would be how the breaks are engaged?

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    The more I look into this, I'm thinking a selonoid. There is a piece connected to a spring on the back of the motor, which connects to a square box. If I hold that up the table spins freely. I took a quick glance at a blow up diagram and it would appear that is a selenoid. So either the selenoid is bad, or the control circuit. However, given the buzzing and the puff of smoke originally in the vicinity of the reel hub, what do you think?

    Otherwise the reel table is a little bit off balance as I look at it spinning, but I am not sure if that can either either be compensated for, (assuming I get this thing working) or if it will matter (assuming the wow/flutter isn't too much an issue)

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    Took the cover off. Neither solenoid fires. Also, the motors both turn, at the same speed and in the same direction no matter whether in REW FF or PLAY. So, it's not as easy as the solenoid, it must be electronic now. If anyone can tell me where the motor control circuitry is, maybe it's an obvious problem. I recall a thread here about a small 2pf capacitor going bad, will have to search that thread....

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    Well, found a fuse missing on the main board, replaced that, but no difference. The motors all turn (left clockwise, right counter-clockwise) if play engaged. The right will go if FF/ left if REW. None of the solenoids will engage either. Motors turn at same speed no matter what function engaged, and regardless of the L-H switch setting. (That is they look to be going same speed, eyeballing it.) So more digging...

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    So, got a schematic. Fuse number f701 keeps blowing. This segment provides power to all the solenoids. The fuse is on the 0AC side, there are two "postive" AC's going to a relay prior to the bridge rectifier. This segment of power supply seems to be fairly isolated, the solenoids all connect via a plug and the AC appears (as best I can follow the spaghetti) directly to the transformer. (Don't have that part of the schematic.) Any way, seems to me the fault must be in this pwr supply segment, unless I am missing something. The only other connection to any part of hte main control board is the coil on the relay. Disconnected the connector fo rthe solenoid, fuse blows. Replaced the cap on the other side of the rectifier, fuse blows. The relay seemed to have some leakage in the coil not quite shorts in it but not infinite resistance either. (I am not sure if normal) so going to replace that next and the bridge rectifier. Will keep updating here, but as always, open to suggestions.

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    In case anyone is following this thread. Replaced the bridge rectifier on the pwe supply for the solenoids. They now fire and that seems to have fixed teh transport issue. It was iffy at first, but last few times no problems. Not sure if the relay is sticking in there or not. So for now, seems to be fixed... Having a schematic makes all the difference... Have not tested the deck further yet.

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    Don't know what the smoke was from originally... Hasn't smoked since, and I'm guessing that maybe there was some dust or something, or maybe some friction on the brake. Apparently teh machine had sat for quite some time. Don't know its pedigree at all. Looks really good on the outside however, although some evidence of wear on the heads and lifters.

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