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Video output MSX Omega

By alex3331

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03-08-2022, 17:34

Hello,
I want to share my problem. I have built an MSX machine Omega designed by Sergey K. It has a 8-pin DIN standard connector, which has RGBS output. I am using upscalers GBS-8200 and GBS-8220 , but cannot get decent stable picture on any of them. I checked with the scope all signals to make sure there is no wiring error. Synchro signal is clean (TTL level), RGB are somewhat weaker ~ 1 volt peak-to-peak. The picture starts, then every 30-45 sec there is a 'No Signal' message, then it comes back and so on. I tried to pick up RGB directly from V9958 video processor, but it does not change anything. My upscalers work fine with my Sharp MZ-700/800 and Spectrum Nuvo. Does anybody know a practical way of solving this problem? What kind of 15 kHz RGB monitor do you need? Never had such a stubborn machine.

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By Pentarou

Champion (486)

Pentarou's picture

03-08-2022, 18:32

alex3331 wrote:

Synchro signal is clean (TTL level)

Strange, the DIN connector doesn't have TTL sync, only composite :-/

Anyway, your problem seem the same as this: https://www.msx.org/forum/msx-talk/hardware/gbs-8220-loosing-signal-every-18-seconds

Try the solutions posted by ~mk~ at the bottom of the thread.

By alex3331

Supporter (9)

alex3331's picture

03-08-2022, 19:37

Thank you for a good link. Yes, I use composite sync; I take it directly from pin 6 of VDP(CSYNC). I checked it - it is ~15,600 negative + 60 Hz negative
I already installed 100 ohm resistor to synchro.

I will continue this effort, but my question remains - if not GBS8200 - then what are people using for MSX RGB?
Thanks

By Pentarou

Champion (486)

Pentarou's picture

03-08-2022, 20:14

I guess most Europeans use a TV with SCART socket. ¯\_(ツ)_/¯

Do you have an 9938 or 9958 installed?
Have you tried taking the csync from pin10 of the CXA1645 instead? (i.e. after R27)

By alex3331

Supporter (9)

alex3331's picture

03-08-2022, 20:41

9958; Will try (I think I already did). I always prefer RGB over any TV - much crisper picture. When I decided to make an Omega I was not aware of upcoming video problems.