Re: Power and control of Mistubishi LT-70 Linear Turntable

Julian, I have a Danish language copy of the service manual for the system. Schematic seems to be complete; you should be able to figure out everything from that.

I can send it to you if your gmail address is capable of accepting attachments. If not, send me another address that does and I'll send it to you.

Dave M

Julian Bunn wrote:

This turntable was part of an integrated system: I only have the > turntable and am trying to figure out how to make it work standalone. > > However, the turntable never spins, the "Start" button has no effect. > I think this is because I am not providing the correct signals on the > pins marked "SYNC", "AF" and "STP" (shown on the main unit schematic). > > Finally, pin 26 also looks like an output, some sort of current source > from Q221?

Pretty sure that pin 26 is just digital; IC152 (CPU?) outputs a signal, IC151 inverts it, and Q221 inverts it again.

I'm at the limit of my expertise with this - can anyone suggest how to > connect pins 24,25,26?

My guess: Let 25 and 26 float.

Ground pin 24 to power supply ground in an easily-disconnectible way, and press the "Start" button on the turntable. If nothing happens right away, disconnect pin 24 from ground.

If grounding pin 24 didn't do anything, connect it to +12 V in an easily-disconnectible way, and press the "Start" button on the turntable. If nothing happens right away, disconnect pin 24 from

+12 V.

Any ideas about what "SYNC", "AF", and "STP" might mean in this
> context?

I bet "STP" means "Stop". On the receiver schematic, it seems to be a diode-OR of three things, one of which is labeled "TUNER" on IC702. The receiver may have used this to stop the turntable when some other source (tuner, tape) was selected. My guess is that this would have shown up on pin 24 of J106 at the turntable.

"SYNC" may be a way for the turntable to tell the receiver that it was ready to go, so the receiver could unmute, start a tape deck, or something like that. On the receiver schematic, the "SYNC" line goes (among other places) into the "muting" block, through diode D7B3. My guess is that this is either pin 25 or 26 on the turntable.

"AF" I'm not sure of. On the receiver, it goes to "A in PLAYER" on IC702, and also seems to be an input to a diode-OR. It may tell the receiver that the turntable is present and on, whether or not a record is currently playing. My guess is that this is either pin 26 or 25 on the turntable - whichever one SYNC isn't.

Matt Roberds