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Unique S-100 computer (Z-80/Vector Graphic/Micropolis)

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  • nullvalue
    replied
    Originally posted by deramp5113 View Post
    Measure the system supplies (-16v, +16v, +8v) and see where they are. If they look fine, then look on the boards and check the voltage of any onboard negative supplies and see if they're correct.
    I checked the rail voltage and it does not appear that I have a stable -16v on pin 52. I'll check it one moment and it's fine (like -18v) and the next it's gone. Guess I'm going to have to replace the power supply or at least part of it? What's the current best approach for doing this?

    Leave a comment:


  • deramp5113
    replied
    Originally posted by nullvalue View Post
    Good tip - I'll check that out. However, the cap was on the Bit Streamer board. The system is not booting even without the Bit Streamer installed. Since I do have some (uninitialized) video, wouldn't that point to a problem being on the 12K PROM/RAM or Z80 CPU?
    It really doesn't matter on what board you cause a power supply short if that short, in turn, damages the system power supply. Though with a 7912 in between the short and the system -16v supply, it would not be typical to get past the regulator in a catastrophic way. The short may have damaged the negative supply on another board.

    Measure the system supplies (-16v, +16v, +8v) and see where they are. If they look fine, then look on the boards and check the voltage of any onboard negative supplies and see if they're correct.

    Mike

    Leave a comment:


  • nullvalue
    replied
    Traced what I hooked up to. The negative end runs to the VEE pin of a 1488P chip. It's carrying -12v.

    Leave a comment:


  • nullvalue
    replied
    Good tip - I'll check that out. However, the cap was on the Bit Streamer board. The system is not booting even without the Bit Streamer installed. Since I do have some (uninitialized) video, wouldn't that point to a problem being on the 12K PROM/RAM or Z80 CPU?
    Last edited by nullvalue; April 30, 2020, 08:11 AM.

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  • deramp5113
    replied
    Look on the schematic for the cap you attached to so you can determine what shorted to what. Is the negative side of that cap actually ground or is it possibly a negative supply? I've done that before with an older scope for which the probe ground is a hard ground and shorted out the negative supply.

    Mike

    Leave a comment:


  • nullvalue
    replied
    Well, crap. Not sure what just happened but I busted something. Just was hooking up the scope to the Bit Streamer. Put the ground lead on the negative side of a cap, tapped the probe to the positive side and the screen went to random characters. Now the machine won't boot to the monitor anymore. Just uninitialized garbage screen. Same results with or without the Bit Streamer. There was no pop/smoke or anything like that. I know I didn't touch anything else on accident. Ugh what have I done...

    Edit: retraced my steps... There's a via just above the negative end of the cap - that via runs to +5. My alligator clip must have shorted the two. Have just the Flash Writer, 12K PROM/RAM, and Z80 CPU boards installed. All regulators check out. What else can I check?
    Last edited by nullvalue; April 28, 2020, 05:34 PM.

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  • nullvalue
    replied
    At the S100 end, should I be following DB25 pin 2 or 3? I always get the 2 confused.

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  • deramp5113
    replied
    I've had very inconsistent results with USB serial adapters at 110 and 300 baud. I'd set the Bitstreamer to 9600 baud.

    Mike

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  • deramp5113
    replied
    That is why I am asking about a terminal versus a PC. Since a modem provides all handshake lines, it's quite possible that a terminal works fine with a modem but that same terminal may not work with a computer that is not asserting the required handshake lines on the required pins. I have seen you refer to it as a "terminal" in these recent posts, so I needed to know what your terminal actually is.

    Since your terminal is a PC running Teraterm, and Teraterm is happy in three-wire mode, we can rule out an improperly driven or wired handshake line as the issue for data not reaching the Bitstreamer. That information helps. I'd now use a scope to probe the data-in path from the DB-25 connector, through the ribbon cable, DIP socket, jumpers, receiver, and to the 8251 in order to pinpoint where reception fails.

    Mike

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  • nullvalue
    replied
    I was also able to verify the ribbon cable bringing the signal from the DB25 port to the 24-pin DIP socket works for all pins/lines.

    Leave a comment:


  • nullvalue
    replied
    Using a PC w/ TeraTerm with a USB to Serial converter. DB9 to DB25 cable. Tested the same adapter & cable by plugging in an external modem and am able to read/write to it - so I don't think the problem is on the terminal end or with the cable.
    Last edited by nullvalue; April 28, 2020, 10:42 AM.

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  • deramp5113
    replied
    We have to know more about what you're using for a terminal and the data cable in order to determine where the problem may be.

    If you are using an actual terminal, it is quite possible the terminal is not transmitting if it's not seeing a handshake line it requires. Or are you using a PC and terminal emulator? How is your data cable wired from end to end?

    Mike

    Leave a comment:


  • nullvalue
    replied
    Originally posted by deramp5113 View Post
    Actually, this will be easier...
    Type "O"UT 06 31 and you should see a "1" show up on the terminal.
    Type a "1" on the terminal keyboard and then do an "I"N 06 and you should see a 31.
    Ok this looks like progress.. "O" 06 31 does produce a "1" on the terminal! However after typing the "1" on the terminal, and an "I" 06, I only get "00".. So I'm able to transmit but not receive at the moment. Terminal settings are baud: 300, data: 8 bit, parity: none, stop: 1 bit, flow: none. I tested the terminal/cable is transmitting fine by talking to a modem. Should I run some continuity tests on the the S100 side or could this be software related?
    Last edited by nullvalue; April 28, 2020, 08:47 AM.

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  • deramp5113
    replied
    Originally posted by MikeS View Post
    Both the 4.0 and 4.1 monitors actually contain a minimal terminal program (E command) that makes this sort of troubleshooting a little easier (at least it helped me sort out the com ports on the Bitstreamer II and ZCB
    The E command did not work for him because it uses the serial port at I/O address 4/5 and there is not an easy way to put the serial port on the Bitstreamer-I card at address 4/5.

    Mike

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  • MikeS
    replied
    Both the 4.0 and 4.1 monitors actually contain a minimal terminal program (E command) that makes this sort of troubleshooting a little easier (at least it helped me sort out the com ports on the Bitstreamer II and ZCB

    Leave a comment:

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