[sdiy] Very OT: direct drive turntable troubles...

[Grant Richter]

Sounds like you have a shorted transistor in the multiphase linear motor
drive circuit.

> From: Trevor Page <trevor at resonance.fsnet.co.uk>
> Reply-To: owner-synth-diy at node12b53.a2000.nl
> Date: Mon, 2 Apr 2001 10:01:39 +0100 (GMT+01:00)
> To: synth-diy at node12b53.a2000.nl
> Subject: [sdiy] Very OT: direct drive turntable troubles...
> 
> Hi all,
> 
> Sorry for being OT - suggest that any replies are off-list. I'm a bit stuck
> with a problem I have with a direct-drive turntable and there may be someone
> on this list who knows a thing or two about turntables and can help me!
> 
> It's a Toshiba turntable. Massive motor on the underside (why do they stick
> washing machine motors on these things anway? :-). Problem is - the motor just
> seems to take ages to get to the correct speed (well a few seconds) and if you
> even touch it very, *very* slightly - it will slow, and needs a small time to
> get to speed again. Seems that there are no gears inside (like with some DD
> turntables) because you can effortlessly stop the platter or even spin it in
> the opposite direction while the motor is running. Seems that the motor does
> not have the torque it should have.
> 
> Another odd thing is the strobe lamp on the side. This lamp actually dims when
> the platter is speeding up and then instantly brightens when the platter has
> reached the correct speed. The stroble lamp therefore instantly dims slightly
> when you touch the platter lightly. This even occurs when I touch the record
> that has been placed upon a slipmat.
> 
> Both the strobe lamp and motor are AC driven from a mains transformer inside.
> Seems that when the motor is spinning up, it draws excess current from the
> transformer resulting in the voltage drop that causes the strobe lamp to dim.
> This doesn't seem right: maybe the transformer is a dud? Where should I go
> from here?
> 
> The deck is totally usable if you just want to play records - but no good for
> mixing, which is what I'm using it for.
> 
> Could the speed control circuit be to blame at all here?
> 
> Many thanks in advance for any help on this matter!
> 
> ~ Trev
> 
> 
> 
> 
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