GBS-8220 fuzzy and green

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BigEvilCorporation
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GBS-8220 fuzzy and green

Post by BigEvilCorporation » Sat May 28, 2016 5:51 pm

Hi!

Since moving house and setting up my dev environment again, my beloved GBS-8220 CGA to VGA board is outputting a garbled green screen. Does anyone have any experience with these boards?

I've verified that the Mega Drive, scart cable, Sync Strike, and the two VGA cables are not the problem; they all work with other machines and output devices.

Also the menu appears fine, I can navigate the options and reset back to factory state (the first thing I tried), it's just not handling input from my Mega Drive.

Image

The board itself seems to be in ship shape, but other than bad capacitors I don't really know what I'm looking for.

Image

Any ideas?

Cheers
A blog of my Megadrive programming adventures: http://www.bigevilcorporation.co.uk

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MintyTheCat
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Re: GBS-8220 fuzzy and green

Post by MintyTheCat » Mon May 30, 2016 9:35 am

Hi,

have you got a scope or anyway to sample the MD's video?

It could well be that you have not configured the Gonbes correctly. Can you take photos or list the settings? I can tell you exactly what I use when I get home.

If you cannot get it to work I have a few of these, pass me your address and I will post you a replacement. I use exactly the same board as you but I have a number of upscalers that I use for MD work.

Cheers.
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BigEvilCorporation
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Re: GBS-8220 fuzzy and green

Post by BigEvilCorporation » Sun Jun 12, 2016 11:56 am

Hey!

I'm afraid I don't have a scope or any other means to test it, and my electronics knowledge doesn't go beyond resoldering capacitors.

I'll get a photo of the settings, but there's not a lot I can get wrong - it's just input type, output resolution, panning and contrast, that sort of thing.
Last edited by BigEvilCorporation on Sun Jun 12, 2016 12:08 pm, edited 1 time in total.
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BigEvilCorporation
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Re: GBS-8220 fuzzy and green

Post by BigEvilCorporation » Sun Jun 12, 2016 12:07 pm

Image

Image

Image
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Charles MacDonald
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Re: GBS-8220 fuzzy and green

Post by Charles MacDonald » Tue Jun 14, 2016 3:10 am

I'd try gently pressing on around the edges of each of the surface mount chips to see if anything changes. That would indicate a bad solder joint where a pin isn't contacting the pad on the PCB well. Or press gently on the PCB to flex it a bit and see if there's any changes.

I know the cables and Genesis are good, but have you tried any other consoles through the GBS-8220? (say a SMS or SNES or something) to verify that it works at all?

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MintyTheCat
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Re: GBS-8220 fuzzy and green

Post by MintyTheCat » Tue Jun 14, 2016 5:00 pm

Hi Matt,

I am not sure what schematic you have for your connections but I found that if you set the resolution to anything other than 1360x768 it will fail for me too.

My settings are as in the photos below:

Image
Image
Image

Try that and if you still have issues we will have to look at your schematic and go from there. Are there any Scopes or people who can handle Electronics at work or who you know locally?
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BigEvilCorporation
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Re: GBS-8220 fuzzy and green

Post by BigEvilCorporation » Fri Jun 17, 2016 7:59 pm

I've tried pressing down on each chip in turn, and bending the board slightly, but no change in the signal at all.

I'll fetch out the Gamecube and give it a whirl.

There's probably some people at work who might have some gear, a few are into robotics.
A blog of my Megadrive programming adventures: http://www.bigevilcorporation.co.uk

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MintyTheCat
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Re: GBS-8220 fuzzy and green

Post by MintyTheCat » Fri Jun 17, 2016 9:06 pm

BigEvilCorporation wrote:I've tried pressing down on each chip in turn, and bending the board slightly, but no change in the signal at all.

I'll fetch out the Gamecube and give it a whirl.

There's probably some people at work who might have some gear, a few are into robotics.
Ok, but from the photo you took I can see that your resolution mode may be an issue. Have you got the circuit's schematic for your connector and the sync generation?

What happens when you try different resolutions - for me only one of them works.
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