Mitsubishi LT-70 Linear Tracking Turntable

This is an LT-70 that at one time was part of the Mitsubishi “Audio Intelligent System Model DA-L70/LT-70”. I am trying to get it to work standalone.

LT-70

On the back panel, there are phono outputs for the cartridge, and an 8-pin DIN plug that connected to the rest of the system.

DIN plug

The wiring is as follows:

  1. Pin 1: Yellow -12V
  2. Pin 2:  N/C
  3. Pin 3: White (“AF”?)
  4. Pin 4: Orange +12V
  5. Pin 5: Black (“SYNC”?)
  6. Pin 6: Braid 0V
  7. Pin 7: Red (“STP”?)
  8. Pin 8: N/C

This plug is marked “TO CACEIVER” J106 on the following schematic for the turntable:

LT-70 schematic (part)

The same plug is marked “PL CONT” on the schematic for the main unit:

DA-L70 Schematic (part)

Working from the schematics, I saw that the turntable uses a -12 0 +12 power supply, which I’ve duly connected to pins 1-6-4 on the plug (29,28,27 on the turntable schematic). Sure enough, the unit powers up, the track indicator 7seg LED lights up, and I can operate the tray using the “Open” button on it, the fwd/rev buttons that move the cartridge left/right, and the various programming buttons on the tray (track select, program, etc.)

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).

Two of these three pins (24 & 25) are connected to IC151, a BA612 quad driver, on the turntable circuit board: 24 seems to be an input signal to the turntable (since it goes to a BA612 driver input, pin 2). The other, 25, looks like an output signal from the turntable to the main unit, and measures +12V when the turntable is powered up. Finally, pin 26 also looks like an output, some sort of current source from Q221?

EDIT (April 2016): I don’t know what I was doing wrong above, but I just checked three years later, and the unit works fine using the connections specified above. I was able to play and listen to an LP without problem.

Summary: open the DIN plug connector on the cable coming out of the unit, and connect the following wires to a 12-0-12 power supply.

  • Yellow to -ve 12V
  • Orange to +ve 12V
  • Braid to Ground

Connect the RCA plugs (left and right) to your amplifier.

The red wire, if touched to +12V, will stop playback, but it’s not required.

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