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  1. falter

    Homebrew Z80 No. 3

    Z80 A0 -> CTC Pin 18 -> SIO Pin 34 and to Both PIOs Pin 6 Z80 A1 -> CTC Pin 19 -> SIO Pin 33 and to Both PIOs Pin 5 And that's SIO Pin 33 not Pin 32. Hope that helps!
  2. falter

    Homebrew Z80 No. 3

    So far for the 74LS139: Pin 9 -> Right side PIO Pin 4 Pin 10 -> Left side PIO Pin 4 Pin 11 -> SIO Pin 35 (not 33) Pin 12 -> CTC Pin 16
  3. falter

    Homebrew Z80 No. 3

    I will trace these out tonight. Thanks so much for doing this... love seeing the detective work happening! I've shown it off in a video in my youtube channel and about 90% of comments think it's something phone related.
  4. falter

    Homebrew Z80 No. 3

    I can take more detailed pictures of the inside of the keypad box if it helps. I had originally suspected the phone cable wiring going into the keypad box connected to the power supply and that the power supply in the keypad box powered the computer. Wasn't an unreasonable guess I figure as...
  5. falter

    Homebrew Z80 No. 3

    I feel pretty confident the keypad and computer go together. But I think the keypad was used before the computer came along with something else. I'd power it up but without the computer being functional it's pointless.
  6. falter

    Homebrew Z80 No. 3

    One other question.. the EPROM this computer has, has a gold strap that runs from the EPROM window and looks like it connected to a gold leaf in the middle of the chip. Does that have any impact on performance of the chip? I assume no.. I've seen other chips where this link is broken. I...
  7. falter

    Homebrew Z80 No. 3

    Thanks for your thoughts! I did get some better pics of the mainboard. They are here. So my suspicion about the EPROM socket on the far left being the place the EPROM originally was is likely correct. The second socket from the left is full of dust, indicating nothing was installed there for...
  8. falter

    Homebrew Z80 No. 3

    Man this thing is strange. So I think I was wrong about the connections between the computer and keypad. There is a power supply in the keypad housing. But it doesn't appear to supply power to the computer. That's accomplished by some loose wires. I think, anyway. They keypad actually has...
  9. falter

    Xerox 820 boards

    Very cool to have you here. I have both an 820 and a Big Board II. I've never gotten around to using it unfortunately. I keep hoping to find the original Big Board but they're quite scarce.
  10. falter

    Tandy 2500xl that just keeps getting worse

    Stupid question.. is there anything other than a fault in the switch that tells the floppy drive that a disk is inserted that would cause a 'Drive Not Ready Error'? Also, can I use a drive from another model of Tandy to test? Ie say a 720k from a TL (this, like the 1.4 mb in the SX, has the...
  11. falter

    Computerland BC286 Hard Drive issues

    Thank you. I wonder why copros get so hot but not the CPU. I plugged it back in.. computer works fine..Autocad loaded up (it depends on having a copro). Really glad this machine is all working again with its original hardware.
  12. falter

    Computerland BC286 Hard Drive issues

    I got it! Borrowing from Adrian's Digital Basement, I took the Miniscribe and tested out the movement of the stepper motor and it was quite stiff. I added some 3 in 1 oil, just a little bit, and then worked it in... noticed it was spinning much more freely, and then put it back together and...
  13. falter

    Lightbulb based scoreboards?

    Man I forgot the name of the Jumbotron until now! I remember the fuss over that when the then Skydome in Toronto opened. I think it was the largest in the world at that moment. The one in my blurry pic that was at the old Ex stadium wasn't that I don't think. It was all shades of yellows, and...
  14. falter

    Lightbulb based scoreboards?

    Going to sound like a strange question maybe. When I was younger and I'd go to a ballgame at Exhibition Stadium in Toronto, at the far end of the field they had this screen - I'm pretty sure it was composed entirely of light bulbs, I think, and basically it could do full on video, pictures...
  15. falter

    Homebrew Z80 No. 3

    Nah it's a new GQ-4x4. So far it's been pretty reliable. I guess there's no way to unscramble things.. too many possibilities?
  16. falter

    Homebrew Z80 No. 3

    It's a 2716... I think they're different electrically aren't they? My GQ-4x4 can read 2716s but not 2708s.
  17. falter

    Homebrew Z80 No. 3

    I've covered it.. but unfortunately it came uncovered. And it's reading the same no matter what I do.. sigh.
  18. falter

    Homebrew Z80 No. 3

    Thanks guys! Yeah I'll check the contacts on the EPROM. It's a 2716, the window has been exposed, which in my experience usually isn't a problem, even after years.. but with the FFs sprinkled around I was worried. Hopefully the chip itself isn't damaged. I'll try cleaning the pins, repeating...
  19. falter

    Homebrew Z80 No. 3

    This is my 3rd Z80 homebrew and kind of unusual at that. It has a numeric keypad and I think they built the power supply into the case for it. And then they have an old school 4 conductor telephone plug, which adapts into a modern telephone plug, and I'm not sure but I'm guessing the power...
  20. falter

    Computerland BC286 Hard Drive issues

    Dumb question.. how long should an LLF take on an 40mb drive like this? It's been going over 25 minutes.. and it seems like it's bringing up the same bad sectors over again. Like "bad cyl = 01A7, hd = 02, sec = 0B". it'll hit something like that, it'll carry on ticking away, and then it'll...
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