| Electronics > Repair |
| Vintage chip Programmer : " Micropross ROM 3000U " |
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| pcprogrammer:
Hi Vince, I see you are having fun :-+ Did you verify that the polarity of the sync signals is correct. The image of your scope screen shows them as going high for sync, but it might be that they need to go low. Maybe worth a try. Another option might be to use the CGA/EGA connector (the one with the 5 round pins), but for that you have to combine the sync signals like m k wrote about. Cheers, Peter |
| Vince:
From my google, all sites say CGA has separate H and V sync signals, tehy aren't not combined. There is also consensus for plarity and voltage levels : TTL level, positive pulses, so I am good. If I were using the polarity I doubt I would be able to see text being displayed I think, but I do 8) One thing I could try, is to try to get rid of the rounded rising edge. Seeing as the video board came to life when I fixed the amplitude of the signals.... it means it's picky about those signals. So maybe the rounded corner does upset it.... However I am not sure how I can fix that corner.... :-// |
| Vince:
Just done reading the 5 pages of that French forum discussing the 5000 model the bigger brother of my 3000U. It's a gold mine of information. It gets most interesting starting page 4, at this message : https://forum.system-cfg.com/viewtopic.php?p=159652#p159652 Thread was initiated in 2014, then died that same year, al links are dead (images, documentation, disk images... :palm: ) then was resurrected in 2020, not too long ago, by that guy linked above. He clearly is a one of us... maybe he is on EEVblog I don't know... He shows pics of his 5000... and I actually see his pics, the links are not dead yet :phew: It is most interesting... and most disheartening at the same time. As you can see from the pics of the interior and the outside.... it's similar to mine except, the monitor and keyboard.... they are not meant to be plugged into connectors at the back, no... they are BUILT INTO THE FREAKING PROGRAMMER !!!!!! |O Mini CRT built-int, with its own driving board, custom keyboard with custom function keys that line up with the rectangles I saw / described earlier... Custom floppy disk format as well. This thing is just a giant custom thing through and through. So now I can stop wasting my time trying to display an image...unless I can make my own converter, but I am not that good and can't justify the immense amount of time it would require me to do that anyhow. Then I would have to make a custom keyboard as well... not knowing the protocol and details of the H/W interface used by the original one. No... it's time to give up on this thing.... Or almost : a guy in 2020 said there is an MS-DOS software to drive the programmer from the serial port. So that's how my unit was meant to be driven then. So my only hope is to find this S/W. I stand a better chance of winning the lottery or inventing a time travel machine. Ah, also in 2020 there is this guy who says he worked on the development of this programmer, and has still some documentation and also the assembly code for the 6502 CPU. Wow.... maybe he can get hold of the MS-DOS S/W. Unfortunately he does not seem to respond to people... maybe he died. I hope not. Ah yeah, if I can get the documentation for the GPIB port, maybe I could have some fun with that at least. Better than nothing. |
| pcprogrammer:
Might be a bit of a stretch, but I found this site https://www.vandoeselaar.com/tinkering/modding-a-gbs-8200/ which writes about converting the video board to handle 240 pixel video. It could be that the programmer has such a low res signal, and that the video converter as is can't handle it. |
| Vince:
Thanks for the searching ! :-+ ... but it's way too involved for me, not my comfort zone at all. Not worth the time investment for me... need to be reasonable here. IF someone had a video converter that's meant to be universal, where you get a control panel with knobs you can turns to modify every parameter on the fly to see in real time the effet on the screen, so you can quickly figure out what the parameters are.. then tell the converter to use that, then yeah, would be quick. But I doubt such a converter exists. I did what I could with my scope and frequency meter / counter to figure as much as I could about this video signal... in vain. That's as far as I can take it, for now at least. Maybe once I retire and if all other projects are done... yeah maybe digging out that project would kee p me busy 'til I die... But for now I will call it quis on the video side unfortunately. Looking at the pictures I posted above, and trying to count characters on the screen, it looks like it'a got 42 columns and 26 lines... because the usual 40x25, so I guess they used the standard 40x25 timings and modified them a bit. As for interlacing, looking at my scoping of the signal, and the pics of what it represents on the screen... I think we can at least say that it is not interlaced.... so that's a huge plus, makes things much simpler I guess. I guess if the engineer who worked on the project, who posted on that forum, is not dead and starts replying to people... maybe he has info on the details of the video protocol, or maybe I can find that out by studying the assembly source code he said he had, to see what the CPU writes in the CRT controller chip registers. Hopefully the source code is well commented... Worst case I could spy the data bus and control lines of the CRT chip at boot with a logic analyzer to see first hand what the CPU writes to that chip... OK so that's all for now on this project for now, I am stuck. Remains playing with the GPIB which I can't realistically do until my lab construction has been taken to the next level, with more space and a dedicated /permanent space for my vintage computer. Then in //, try to find a copy of that MS-DOS S/W to control the programmer via the serial port, my only hope. So I will register on that forum and add my bit there.... |
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