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Thread: Something Different - DECTalk DTC03

  1. #31
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    There isn't much that uses the -12V supply. We know that the 1488 does. I'd have to pull the cover off the unit, but I think the only other parts that could use it are op-amps in the audio processing section. I would think that the digital sections wouldn't know a thing about any problems in the analog audio sections. I still would check the eproms for bit rot first.

    Lou

  2. #32

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    If I can find an eprom burner, I will definitely dump them.

    I have fully confirmed that the other unit makes the DTMF tones upon power up because I connected it to my computer speakers. The only problem is that I cannot seem to get my terminal to communicate with it. I am going to double check the serial lines again. I am using my VT-101, and I can confirm that it is in full working order, loop back tests pass and connections to other devices work.

    Thank you so much for all the advice. I really appreciate it.

  3. #33
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    Forgive me if I am pointing out the obvious, but the VT101 connector on the back is DB25M DTE, and the pinout I showed in my tables for the DTC03 brings the lines out to a DB25M DTE also. One needs a null modem cable to connect the two devices.

    My favorite tool to avoid destroying 1488s is the little box with the LEDs at the far right of this picture: http://www.vintage-computer.com/vcfo...chmentid=11437 (pay no attention to the wiring to the cardedge connector, it's wrong!). I plug it into the ends of the cable (or device) one at a time and see who is transmitting on pin 2 and make sure that the other is transmitting on pin 3.

    Lou

  4. #34

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    I do not know too much about the technical side and terminology of RS-232, so at least for me you are not pointing out the obvious.
    To wire it for DCE would I just swap wires like a null modem cable, like in this picture from Wikipedia? http://upload.wikimedia.org/wikipedi...dem_Wiring.png

    What do you call that box? It sounds like it might be a handy tool to have.

    Thanks.

  5. #35
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    That box is sometimes called a breakout box, or LED box. It's trivially simple. Each line passes through the box, it has a DB25M on one end and F on the other. Pin 1 to 1, 2 to 2, etc. Each line (except grounds on 1 and 7 of course) has two leds connected to it. One lights green on mark, and the other one (red) with opposite polarity to the first, lights on space. The leds are connected to ground through resistors. You could make your own pretty easily. This one was my father's that he carried as a field engineer.

    Perhaps you could/should check out your existing cable with your ohmmeter (test light, bell set...). If pins 2 and 3 don't cross in your cable, then indeed you need a null modem adapter (like the one in your link.)

    Lou

  6. #36
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    Quote Originally Posted by Old Computers View Post
    What do you call that box? It sounds like it might be a handy tool to have.
    Lots of different names: {Serial, RS-232, DB25} {tester, checker, line monitor, breakout box}

    This one is cheap at $4 plus shipping:
    Check Tester ( Green/Red light)
    http://www.monoprice.com/products/product.asp?p_id=1209

    This one looks nicer for $15 shipped:
    Black Box QuickTest RS232 Line Monitor w/ D9/D25 Adapters
    http://www.ebay.com/itm/400388309068

    Oh, just found the same one Lou has in his picture, $20 shipped:
    Datatran MT-41 Mini Tracker Plus DB25 Cable Signal Monitor
    http://www.ebay.com/itm/400388307904

    If you want to be able to use jumpers to custom wire the connection you usually want a breakout box, example $25:
    Pocket-Sized RS-232/Serial Break Out Box
    http://www.ebay.com/itm/280852483299

  7. #37

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    Thanks for all of the info guys. I might actually go with building my own box just for the learning experience, but I might go ahead and buy one of the ones on the internet.

    As for the cable I just checked it, and cardedge pin 2 side A goes to the DB25's pin 2, and cardedge pin 1 side B goes to the DB25's pin 3, so I will need the adaptor. I think that I will probably go ahead and modify the cable. Or would you recomend that I construct a null modem adaptor?

  8. #38
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    That Black Box line monitor looks really sharp for the price. It has a little protective case and nice adapters for the ends. Black Box stuff is always really expensive, so you know that device was way more expensive when it was first bought. If I didn't already have one, I'd get that one!

    As for making your own adapter, or re-wiring your cable, it's all a matter of your time, your skill, and your funds. If you are cheap (and have a well stocked junk box), if you consider that this is a hobby so time is irrelevant, and if have good skill with the soldering iron, then make your own adapter or rewire the cable. If any of the above don't hold true, go to radioshack (frys, microcenter, ...) and buy a null modem adaptor.

    Lou

  9. #39

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    That is a nice piece of equipment. That will probably be the one I will choose if I decide to buy one.

    I am probably going to make my own adaptor. That way I can use it for other things when I am not using it for the DECtalk, and it is more fun than buying a pre-made one. Hopefully I can get the parts tonight and work on it this weekend.

  10. #40

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    I made my own null modem adaptor, and it works. Thank you for all the help! When I make a case for it I will be sure to post some pictures. I think now I might make a program to make the synthesizer easier to use instead of using a terminal.

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