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Thread: Microkit 8/16

  1. #21
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    Thanks Dave. I'll check those pins out.. when you say 'boot' are you referring to the load switch?

    I wonder if this bootstrap leader is just like my digital group 8080 loader... minus the message to insert tape. I really gotta get a reader put together here. C8702 is identical to c1702 right? Nothing modified between them?

  2. #22
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    Yes. Boot == load.

    I have just edited my previous post, so worth re-reading...

    Time for bed in the UK so I will catch up with developments tomorrow morning...

    Dave

  3. #23
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    Hi Dave,

    I actually posted a youtube video showing everything but what happens if the memory boards are removed in a previous post.. hopefully it is easy enough to follow. On power up, there is a screen of random characters, often ? marks. On reset, this changes to a ful screen of 9090s repeating over and over again. Also on reset, the enabled light goes off. Run is always lit no matter what. On hitting load, the screen does not change but the enabled light comes on. Hitting reset again, enabled goes off, screen does not change. I'll pull the ram and see what that does.

  4. #24
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    With all cards out, I get a screen full of question marks. The enabled button still turns off on reset, but there's no action on the screen. I added in the RAM cards one by one, same thing, until I got to the last one - the one with the two jumpers at 4 and 6. As soon as that was installed, we were able to get the 9090 etc screen back again. If that is the only board installed in the machine, same thing.

    I tried, just for an experiment, configuring one of the other boards the same way, putting it in by itself, but same thing - 9090s.. no change in behavior.

  5. #25
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    I tried another experiment - removing the bootstrap ROM entirely. The first time I powered up, I got ? marks, and on reset got random stuff being automagically 'typed' onscreen. Second and third time, ? marks, no reset possible.

    So then I thought, ah what the heck.. and I borrowed the 1702 from one of my spare digital group 8080 boards. I wasn't expecting anything to happen, but I think it actually *was* trying to run the code... you can sort of make out the '8080 Initialize Cassette' message the dg machine would normally come up with. I'm not sure if the garbling is the differences in video cards, or indicative of a RAM problem.. but yeah.. that's kinda interesting.

    Pic here.

  6. #26
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    Question - this Microkit has DIN ports on the back for connecting the tape drives... were these connections for tape recorders standardized way back when? Or am I gonna have to figure out which pin is which and then try to find or wire up a specific cable?

  7. #27
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    They were pretty standard back in the day. Even my SW radio has one.

  8. #28
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    Yes, there was a DIN 180 degrees standard for stereo. GND, left and right record and left and right playback.

    There should be some way of controlling the cassette motor I should have thought as well. Any signs of any 1/8” jack plugs anywhere?

    I have done a bit of ‘digging’ today. I need to look a few things up further tomorrow before I do my next post though.

    Dave

  9. #29
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    In one of my photos on google drive there is what looks like an earphone plug. It is attached to the keyboard cable. I thought it was for video.. maybe that is what it is for?

  10. #30
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    Nevermind.. just got a note back from the seller. I had asked them about that plug attached to the keyboard and apparently that *is* for composite video out, not tape. So scratch that.

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