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Thread: Epson QX-10, need help!

  1. #11
    Join Date
    Oct 2016
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    Dutchess County, New York, USA
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    No idea why. There's the pin out above that should provide a clue if wired differently. I've got a QX-16 and haven't found the correct monitor for it. It appears that monitor is a super rare beast and so I purchased a QX-10 CRT and hope to provide the +12 volts it needs to work via an external pwr supply to see if it will support the QX-16. The 16 doesn't have +12 on the motherboard connector to the CRT since the QX-16 CRT had it built into the monitor itself. Just need the time to play with it. I'm also troubleshooting a S-100 system power supply that smoked 8" floppies and it had/has several problems and no schematic. So I'm hand drawing one. It might have been quicker just to replace all except for the bridge rectifiers - 3 transistors, one zener diode, a 75L05 and a 723 regulator.

  2. #12

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    using the original frayed cable from the cpu, power it on w/o the display and measure the plug to see which pin contains the 12V then see if the new cable has 12V on the same pin and verify the grounds as well. If your 12V is gone, maybe the fuse blew again. The frayed cable could be what popped it the first time or the new cable wired wrong popped it this time. The other signal pins are just TTL and won't matter if they get cross-wired except maybe if they got on the 12V line ...

  3. #13
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    Oct 2016
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    Quote Originally Posted by retrogear View Post
    using the original frayed cable from the cpu, power it on w/o the display and measure the plug to see which pin contains the 12V then see if the new cable has 12V on the same pin and verify the grounds as well. If your 12V is gone, maybe the fuse blew again. The frayed cable could be what popped it the first time or the new cable wired wrong popped it this time. The other signal pins are just TTL and won't matter if they get cross-wired except maybe if they got on the 12V line ...
    Yes, the new one might be be a cable for the QX-16 which as I stated earlier didn't use the +12v's from the computer to power the monitor. For some reason Epson made a new monitor for the QX-16 and built the power supply into this new monitor. Perhaps the QX-10 power supply was found to be overtaxed? I don't know if the cable changed also, could be it did. So do check for 12 vdc on the monitor end of the new cable. If not there then check again at the computer.

  4. #14

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    Do you have a scope? You'd have to confirm the signals coming out of the cable. It might need horizontal sync from the pc to actually produce the green raster. Sometimes the sync IS the horizontal drive for the transistor that drives the high voltage flyback.
    There is a Sams ComputerFact for that computer somewhere which gives full detail on all of it. I'll see if my Google-fu can find it. Fred Kraan's site has diagrams too. He linked to it in here already.

  5. #15

  6. #16

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    Apparently my last response here got deleted, so I'm retyping it. I got my hands on a scope and pinouts for the cable. I determined via the old cbale that it works fine except for the severed video line, which is expected given the physical damage. The new cable is completely wired wrong. 12v is sent down the wrong line, basically nothing is in the right place. I have the option of refunding it and trying to source another. Or fixing it myself. Not sure what is best, I don't know anywhere else that sells these.

    I was horribly afraid they'd wrecked my CRT but it gives the same response with the old cable plugged in as it did before the new one arrived, so I think it survived.

  7. #17

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    Good news! I used a schematic I made for the cable, pulled apart the DIN shell, and rewired it to the correct pinout. I got video!

    https://i.imgur.com/EIqopL6.jpg

    It's not perfect, I think there is some sort of horizontal sync issue I need to start debugging, but it's progress. It also loads disks and the keyboard works. Anyone have any idea where I should start looking for getting this monitor dialed in? My friend says it's possible vram issues, which is another thing to consider.

  8. #18

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    Also, I know I'm triple posting, which I'm sure is frowned upon, but I'm working on Revelations as they come. I visited a standard CPM disk and recorded how it acts when typing. I also reseated all of the vram chips.

    https://streamable.com/mxwuo

    It repeats every 4 characters in an odd pattern, and my friend suggested that since I shuffled the memory chips around, there's likely a 74x series chip at fault. There's also 7 capacitors, most of which are leaking, that I plan to replace. Does anyone have any advice?

  9. #19

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    The problem isn't at the video ram, it's after when it's being converted to analog video stream. I would look at the chips on the Q10 GMS board and see if one is described as a shift register. The technical manual describes the video as clocked in serial via a shift register. You positioning is off by 4 which is a power of 2.shift register.JPG

  10. #20
    Join Date
    Oct 2016
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    Like retrogear said above, not video RAM. RAM issue would show up as strange missing or always on (constant) video dots on the display.

    Repeat characters would be keyboard keys producing two outputs for one press or problems in the keyboard input to video memory conversion. If only some keys repeat then keyboard might need key contacts cleaned. Also, does any of the computer responses to your input have extra or missing characters too? If not, then look at how the keyboard input gets put into video RAM. Good clue above from retrogear (again).

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