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Thread: Epson QX-10, need help!

  1. #21

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    Thank you so much for this information! The computer responds completely normally, i was able to run a dir command and type normally, if i ignored the garbled output. It seems to solely be a video problem. I have a copy of the schematics for the video board and can look for information about the shift registers. I'm using this one:

    http://web.archive.org/web/201412300...X-10%20GGS.pdf

    Is there anything else you would recommend to help me troubleshoot thing? I know my link is for a "GGS" board (as mine is labeled), how does that differ from the GMS? It has two shift registers (9E and 10E) so should I start there? Thanks again for your help
    Last edited by username1; November 7th, 2019 at 08:47 AM.

  2. #22

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    since you have a scope, even better if it's a dual trace or external sync input to the scope, you need to sync the scope to the video output at the horizontal sync rate and see where the 2nd delayed ghost image starts then walk around those waveforms on that GGS board and see what pulses line up horizontally with the ghost and follow it back to it's origin. Hard to explain what I mean with just words, say H is horizontal sync, Y is normal character Z is ghost. In a horizontal line it's HY...Z sync on H so Y is on the left then see with another scope trace what pulse lines up with Z, then follow that path back to source. Best to see on scope if you just clear the screen by pressing enter a bunch of times so only prompt (Y) char on left side up/down the screen and one ghost (Z) prompt.

  3. #23

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    Retrogear, thanks for the advice. I tried my best to follow what you said but I don't think I get it. This is my first time using a scope for any real work so maybe you need to dumb it down a bit. It is dual trace, but I couldn't work out how to sync the waveforms like you said. However, I did recap the video board, but it changed nothing. I used the diagrams I have in the schematic book to check as many waveforms as I could and they looked pretty ok. I'm not entirely sure what I'm looking at, though...

    https://imgur.com/a/pZzOTdR

    This is the video waveform here. Along with a photo of the display on booting CPM. The waveform does look kinda funky, even though I only used one probe, it kinda looks like I have two, which I don't understand. Maybe that's part of the issue. This might be a bit out of my depth so if you know anyone I can ship this board to and have it repaired I'd possibly be interested in that too. Otherwise, any light you have on this would be much appreciated!

  4. #24

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    We'll see how far we get with this. Can you get access to connector CN10 on the GGS board while it's running? Pin 18 has the horizontal sync pulse, positive going. See if you can get your scope to show a positive pulse on your trace like it shows. Set your scope to + slope. If you show me the face of your scope I can point a few things out. Do you have an input called EXT SYNC or a second channel? You will need to get that sync pulse on there and set your scope to sync on that. Probably tack a wire on it so the scope can be clipped to it for a reference. Then you need another probe to walk around and test some points. I've highlighted video on CN10 pin 6. If you scope is locked on the sync, then looking at the video you should see video pulses with a ghost of it to the right. I'm on vacation right now so may or may not get back to you right away.sync and video.jpg

  5. #25

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    Thanks again for your incredibly helpful information. For now I will post a picture of my oscilloscope that I am borrowing. It does have a BNC plug on the back labeled (EXT TRIGGER) https://i.imgur.com/QrzHlzd.jpg. until you get back to me on the scope I'll see what I can work out in the mean time
    Last edited by username1; November 13th, 2019 at 09:38 AM. Reason: Additional info

  6. #26

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    that's a nice scope and more features then I've ever used. I'm looking at the manual. It's a dual trace scope so you will need 2 probes to do what I'm suggesting.
    You would select Edge Triggering, positive going edge, trigger on analog channel 1 connect to pin 18 then look at channel 2 with the other probe on pin 6edge trigger.jpg

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