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  • Joined: 30 Mar 2018
  • Posts: 6
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Sega mark 3 color issues
Post Posted: Sun Jul 12, 2020 12:11 am
Hello,

I'm hoping anyone on here may have an idea of what to look at next for this strange color issue I've been having with my sega mark 3 that I have been trying to repair.

I got this system a while back as-is and found that the only issue is a weird color issue that I at the time assumed was just a capacitor issue.

So at this point I have done the following

-checked video with RF and A/V
-tried different power supplies
-different tvs
-reflowed every solder point on the board
-replaced every capacitor
-replaced the BA7230LS chip

But this weird color issue still persists on the system with the two games I have of Phantasy star and Hang-on. The games play and sound completely fine but sometimes it seems like the system isn't sure what color to use for a specific portion of the screen. Like in Hang-On the sky flashes between white and black for the first stage, but the player bike and the other racers seem to look fine.

I was also wondering if it could be an issue with a one of the RGB colors, but the system is still capable of showing reds, blues and greens.

Any advice would be greatly appreciated!
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  • Joined: 01 Feb 2014
  • Posts: 529
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Post Posted: Sun Jul 12, 2020 6:35 am
Have you tried it on a different screen? Also, does the sky colour go instantly to white/black or does it sort of quickly fade there?

I had a similar issue once with an old CRT screen of mine. Everything worked just fine, but in games that used the 'bluest' blue 0000FF (e.g. the sky in Alex Kidd or Hang-On) it weirdly flashed between black and white. Other screens did not have this issue and using an RGB cable with some resistors in it eventually fixed it for the one in question, too. Apparently, the SMS produces a very strong RGB signal some screens have difficulty to cope with.
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  • Joined: 30 Mar 2018
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Post Posted: Sun Jul 12, 2020 8:11 am
I've tried it on two consumer tv sets and a pvm monitor with av and rf. Same issue on all three.

I haven't tried it with scart RGB yet as I didn't have a cable, but I do have one ordered.

For hang-on specifically, the sky actually starts out as black and flashes between black and white as you play the game. So that part seems similar to your example.

I'm hoping actually using the RGB will fix it, but the fact that both RF and av give me the same color issues on multiple TVs makes me wonder if something is wrong with the video encoding.
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  • Joined: 30 Mar 2018
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Post Posted: Fri Jul 17, 2020 3:59 am
So I did finally get some scart RGB cords and can verify that it still has the same color issues even using RGB....

Does anyone else have any ideas on what components to check?
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  • Joined: 30 Jan 2007
  • Posts: 271
  • Location: San Jose, CA
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Post Posted: Fri Jul 17, 2020 6:54 pm
It might be a bad VDP, there aren't a whole lot of components going from the RGB output pins to the BA7230LS (just six resistors and three caps), and you've already recapped the system so we can rule that out.

Thankfully the VDP in the Mark IiI is the same one used in the SMS so a swap should be easy to do.
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  • Joined: 30 Mar 2018
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Post Posted: Wed Jul 22, 2020 1:46 am
So Apolloboy was right!

The issue was the VDP!


I finally have a properly working Mark 3! Thanks again for all the help.

Though the issue is that now my Master system needs a working VDP... But hopefully I can find someone with a spare one or a for parts system.
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