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Thread: Otari MX80 remote shenanigans

  1. #21
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    Quote Originally Posted by ecc83 View Post
    Just short out the trimmer. The voltage will be low but you can 'tack in' various values until you hit 5V +-say 5%. In fact the only reason a trimmer was used I guess was to save this process in production? Much better to find a fixed value. Try 3 values, do a graph!
    Dave.
    The trimmer seems to be working correctly. However, pin 2 of the STK772B just popped off the solder pad. Whether it was intermittent before and that has caused it to go screwy, or whether it has just broken from being handled too much over the last few days, I couldn't say. The chip is weighed down by a massive heatsink and is just dangling off the pins and I was afraid something like this might happen. I already have a DC-DC converter due to arrive, so at this point I'm more interested in replacing it, though it might make an interesting project for the future.

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    OK. Update for those who are interested. As part of my project to design and implement a replacement PSU board, I got a miniature DC-DC converter and components to make a simple crowbar circuit using a thyristor. The other purchase was a bench power supply, because until recently I've not done enough electronics work to merit having one.

    Long story short, my replacement board did not work. Probably something slightly wrong with my understanding of the pinouts from the deck, because it works perfectly on the lab supply, but absolutely nothing happens when it's installed in the remote. So, for the last few weeks I've been chugging along with the remote powered by USB.

    Tonight I had the bright idea of plugging the original Otari PSU board into the lab supply to see what it did. And by doing this I managed to get it to output a stable 5.0 volts from a 24v input, so the original PSU is now back in the remote and after some repairs it appears to be working nicely again, without blowing the fuse. This is with the transport control plugged back in too - I had to disconnect it when using USB power because the lamps were overloading it, I think.

    Anyway - the cause of the problem is that some of the pins on the STK772B were making intermittent contact - a knock would disconnect them and at some point it received a hard enough knock to disconnect it permanently but about 0.5mm from the solder pad so that you can't see it was broken. My guess is that it was one of the feedback pins, and as a result it was outputting some incorrect voltage and tripping the crowbar. Having reconnected and reflowed the solder joints to the regulator chip, it outputs a suitable voltage and the remote is working. Or seems to be - I haven't yet done a recording so I guess I'll find out in a few weeks. I can set it back to USB power if necessary.

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  4. #23
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    Long road to get back to the same place......but sometimes that's what it takes.
    Glad you seem to have it sorted out...but post back after you use it for awhile.
    It's certainly something to keep in mind for the rest of us MX-80 users.
    Thanks for the update!

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    Question Cable type - some specification

    Please can you help me? Which cable is used to connect an OTARI MX-80 to a remote OTARI CB-124?
    thanks,

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    Please can you help me? Which cable is used to connect an OTARI MX-80 to a remote OTARI CB-124?

  7. #26
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    Quote Originally Posted by fabrizio iorio View Post
    Please can you help me? Which cable is used to connect an OTARI MX-80 to a remote OTARI CB-124?
    thanks,
    Hopefully Miroslav can comment because I think he has one, but my understanding is that it's an RS422 serial interface. Rumour has it that it might need two cables, but that may only be for 32-channel operation or something.
    On the CB140 I think it uses a 25-pin serial cable, and they might be wired 1:1 with the tape deck, but I wouldn't risk it without checking, because some of those pins are 24v power lines and will likely destroy the serial transceiver chip in the remote if they go into the wrong place.

    The pinout for the CB140 is this:
    1. Frame GND
    8. GND
    9. GND
    10. Transmit common
    11. Transmit A
    12. Receive B
    13. Receive common
    14. Frame GND
    16. POWER (24V)
    17. POWER (24V)
    19. Tach pulse
    21. FWD/DEV
    24. Transmit B
    25. Receive A
    ...the unlisted pins are not used, and may not even be present.

    Oh, and here's a photo of the actual connector on the CB140:
    https://www.revoxremotes.com/Images/Otari/CB-140_c.jpg

    ...does it look the same on yours? I can check my cable tonight and see if it's 1:1 or not, but as mentioned, there's no guarantee the CB124 uses the same pinout.

    EDIT EDIT: I knew there was something I forgot. The Otari remotes have DIP switches inside which tell it what kind of deck it's being connected to. If the remote wasn't already set up for the MX80, it may not work. It may even be different depending on whether the MX80 is 16/24/32 track. I have no idea, since I haven't yet found a list of DIP switch values online.

    EDIT: And for those wondering, yes, the remote control has been working perfectly since the PSU fix.

  8. #27
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    I usually hijack when tape remotes are under discussion!

    Teac A3440 12 pin rectangular plug please?

    Dave.

  9. #28
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    Quote Originally Posted by jpmorris View Post
    Hopefully Miroslav can comment because I think he has one...
    Pretty much all the info you gave looks to be correct...though TBH, I haven't check against my deck or my manual/schematics because I too busy right now with major floor installation at my house to sit down and go through everything like you did.

    Not sure about the dip switches though...I thought it just depends on the EPROM data. I just can't sit right now to review all that.

    At any rate, the cable can probably be made pretty easily. The connectors are easy to find, and most any decent multi-wire cable would be fine.

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