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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36 thoughts on “Mitsubishi LT-70 Linear Tracking Turntable

  1. Where on earth do you find schematics for an esoteric piece of electronics like that linear turntable? I have an elderly Sansui QRX-3500 Quadraphonic receiver I would like to rejuvenate. If I get that working, I have some quad LP’s along with a 4 channel Shibata cartridge for my Dual turntable.

    I also have a Tektronics 310A and can’t find squat for it. I had a glimmer of hope, but Your link in your scope section has died.

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  2. Just had an idle thought about your “turntable”. I think I have a grip on the concept, linear tracking & all that, I remember seeing them in their day. My question is how were the original grooves on the vinyl cut? Did they use a linearly operated tone arm or one that pivots? If the latter, wouldn’t a tone arm on a pivot be closer to the original?

    I do have a question on my Tektronix 310A, but can’t find anyway to contact you other than by posting a comment – which probably evaporates into the ether 🙂

    BTW old chap, at the risk of being cheeky I can’t resist: birds have wings, cars have fenders 🙂 And besides, your 911 mirrors are on the doors. Now my 1959 AH Sprite has them on the “wings” LOL as did my Honda back in Japan. Does your SLK have the V6?

    Oh well, to use other idioms, its time to take my MX5 out and rev the engine up to its “valve crash speed”.

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  3. Did you ever get the LT-70 turntable working? I have a LT-90 and need the schematic for it and thought the lt-70 would probably work.

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      1. Thank you for your off, JB, but I have found a download online for a reasonable price. They may be the same, but I can get the right one. Glad to hear you got yours working well. Do you mind If I pick your brain if I don’t understand something when I get it?

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  4. Hi guys.
    I have an LT70 and for the life of me, I can’t get the platter off to change the belt. I easily removed the retainer ring, but there is still resistance in terms of completely removing the platter. Any thoughts would be great appreciated.
    Ken

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  5. Hello Julian,

    My name is Pierre and I have a similar turntable ( Mitsubishi LT-90) with the same plug. Did you sort out your TT and does it work now? If so, how did you do? Where did you connect the 8 wires? ( by the way, my plug has 9 wires, one of them soldered to the metallic part) .Did you use 2 power supplies? Thanks in advance.

    Pierre

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    1. Hi Pierre, it’s been a while since I looked at this, so need to look again to refresh my memory. My recollection is that I used two wal-warts back to back to power it.

      Julian

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  6. Hello Julian,
    Thank you for your your fast reply! Yes, it would be great if you could have a look. I am especially interested in reviving the tonearm mechanism ( maybe to transplant it on another TT eventually), but it would be interesting to try the whole turntable. I am not familiar with the technical terminology; when you say “two walwarts back to back”, do you mean two different power supplies? At what voltage / amperes?
    Thanks in advance,

    Pierre

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  7. Hey Julian,
    I am trying to accomplish the exact same thing you have done here for my Mitsubishi lt90 turntable. If you have some free time could you elaborate more on how you rigged yours up to work? Did you ever figure out how to get the turntable to spin? How did you wire the wall warts to provide proper power to the turntable. Maybe you could post some updated pics if you have time. Thanks for any help you can provide me. Take care..

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    1. I’ll take a look this evening. I used two back to back wall warts to give me -12-0-12 supply, IIRC. Once power was supplied, all the front panel controls worked as marked, again IIRC!

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  8. hey Julian,
    just wondering can you give more info or pictures or drawning on the two power supplies you connected.( the way you did it) not sure what you mean or how you connected two wall warts. does this mean you needed 24 volts DC? or did you use two 6v power supply to give you the 12 v ?
    thanks Shawn

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    1. Hi Shawn,

      I used two 12 volt wall warts connected together, to give me a +12V / 0V / -12V supply. Take the first wall wart, and connect the negative wire to the positive wire of the second wall wart: that pair of connected wires will be your Zero volt (ground) terminal, which you connect to the LT70 connector’s ground pin. Then connect the positive wire on the first wall wart to the positive pin on the LT70 connector, and finally the negative wire on the second wall wart to the negative pin on the LT70 connector. OK?

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      1. No, I’m afraid not – you need a ground, to make 12-0-12. You could try wiring two resistors in series across the 24V output, and take the middle of the pair as ground, but it’s unlikely to work properly.

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  9. Hi, JB!
    I have the same story as your one. I own LT-70 but I cannot figure out the pins. So maybe you could make a conclusion about your progress. My questions are:
    1) have you made this device working standalone
    2) what exactly have you made to achieve this result

    BR

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  10. Julian,
    I understand what you did with the two 12vdc power supplies–and which pins to connect them to–but did that make the unit work? I tried to follow the other posts about about the STP (‘stop?’) pin, and some kind of faulty switch beneath the platter, but I still don’t understand if you actually made it WORK! I’m like trojanp in the above post–I have access to one of these, and I’ll buy it, IF it can be rigged to operate as a stand-alone unit with MY receiver….not the Mitsubishi one that it was designed for.

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    1. It’s been a few years since I worked on it. My recollection is that with power supplied as I described, it works. If I get motivated again I’ll pull it out of its box and check!

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      1. Thanks for getting back to me on this–that’s too nice of a TT to just throw it away, because nobody has the proper Misubishi unit to hook it up to….I need another TT like I need another hole in my head–but I look at this as a challenge, if I can buy it cheap enough….

        Liked by 1 person

      2. Hello,
        I have the same turntable as the LT-70, I also plugged two power supplies + 12v 0 -12v (400ma on + and 200ma on the -), but I have the same symptom as you first, This means that everything works except when the tray is switched on.
        I also tried to set to 0v on J106 / 24, it’s the same, at + 12v the deck does not work (stop)
        For now it is disassembled, could it be that an optical sensor blocks the plate if the chassis is opened?

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  11. Plz, any links to service manual? got mine working thanks to this page! I would like to do some maintenance and cal. and I could only get a German version.

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  12. Hello JB, your work here is outstanding and thank you for your efforts.

    I do however have one question, does this turntable use an actual phono input or is the output already amplified so you can use it in any auxiliary input.

    If it requires a phono and put, how did you ground the table to stop noise like majority of the other normal turntables out there usually have a ground cable that connects next to the photo input.

    I just picked one of these LT-70’s up and would like to use it!

    Again thank you for all you’ve done!

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  13. Hello ! I have bought a DA – L90 cassett changer with european contact ( 220 – 240 v ? ) and also bought ( ebay ) LT – 70 ‘s automatic turntable. Can I use the LT – 70 in the L90 cassette changer ? On the LT – 70 there is 8 pin contact and the same on the cassette player. I am also worried about the electrics , 220 – 240 volt in to the cassette changer ( fully working ) and LT – 70 ‘s 120 v or ? It also say only to connect with LT – 70 ‘s system.

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  14. Because I only bought the turntable (LT 70), I wonder if you need the screws that you need to remove when moving on top and bottom. They were not included at the time of purchase. Is it possible to play the turntable disc anyway? Can you find the same size and tighten.

    Thanks ! Because you shared your knowledge with us so we can use this turntable again.

    Stefan / Malmoe / Sweden

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  15. Hello again ! Did not work with the DA – L90 cassette changer / reciver.
    How can i get this to work on its own with out the system DA – L70 ???
    ( Mitsubishi LT – 70 )

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