19" Samsung LCD + GBS-8200 cga to vga converter Problems

perrson

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19" Samsung LCD + GBS-8200 cga to vga converter Problems

Hi everyone,

I'm currently testing a red alert (1981) arcade pcb. It mostly seems to be working except for a sync issue I'm having.

The pcb has both a vertical and horizontal sync and for testing purposes I am using a gbs-8200 cga to vga converter, I do not have anything else to use at the moment.
Currently I have the the vertical and horizontal syncs wired together on the gbs-8200 since the cga input on the gbs-8200 only has composite sync. I posted a video
on youtube showing what I get, link below:

https://www.youtube.com/watch?v=R-8LRz_r27c

As you can see there is a good amount of horizontal scrolling and jitter with static between the images, occasionally there is no signal to the gbs-8200 as well as seen in the video. At first I tried the RGBHV harness and it showed the result from the youtube video occasionally but also had a lot of moments where there was no signal. The youtube video is when I combined both the H and V sync wires together and used the 5 pin connector on the gbs unit which seems better for some reason but not playable.

Right now I am trying to find out if this is the gbs-8200 fault or if its something to do with this pcb. Has anyone had this type of scrolling/jitter from a gbs before?

Any help or ideas would be great. Thanks!
 
Hi everyone,

I'm currently testing a red alert (1981) arcade pcb. It mostly seems to be working except for a sync issue I'm having.

The pcb has both a vertical and horizontal sync and for testing purposes I am using a gbs-8200 cga to vga converter, I do not have anything else to use at the moment.
Currently I have the the vertical and horizontal syncs wired together on the gbs-8200 since the cga input on the gbs-8200 only has composite sync. I posted a video
on youtube showing what I get, link below:

https://www.youtube.com/watch?v=R-8LRz_r27c

As you can see there is a good amount of horizontal scrolling and jitter with static between the images, occasionally there is no signal to the gbs-8200 as well as seen in the video. At first I tried the RGBHV harness and it showed the result from the youtube video occasionally but also had a lot of moments where there was no signal. The youtube video is when I combined both the H and V sync wires together and used the 5 pin connector on the gbs unit which seems better for some reason but not playable.

Right now I am trying to find out if this is the gbs-8200 fault or if its something to do with this pcb. Has anyone had this type of scrolling/jitter from a gbs before?

Any help or ideas would be great. Thanks!

I'm having the same issue trying to hook up a WORLD SERIES BASEBALL to a 32" VGA....my pic does the same thing as yours is shown.
Is there any type of "guide" out there with people whom have been sucessful using this converter and on what games ???


Dave
 
As a test, try putting a resistor in series on the sync line. Some sync levels are a bit too high for the 8200. I've seen 680 ohms being suggested, but YMMV.
 
The resistor was probably my suggestion, you may have to go as high as 1K.

I've seen this issue a lot on my test rig but never did anything about it since
I only use it to confirm a board is working.

Next time I see this I am going to test a sync combiner to see if that works
better than tying the H&V together. I will post my results.

JD

As a test, try putting a resistor in series on the sync line. Some sync levels are a bit too high for the 8200. I've seen 680 ohms being suggested, but YMMV.
 
New converter

I ended up trying a new cga to vga converter and it changed the result but it's still not working properly, I posted a youtube video, here is the link:

https://www.youtube.com/watch?v=iqSLE2vSUJs

I guess at this point I'm trying to figure out if this is the pcb or just the converters, kind of stumped as to what I should do at this point.

Edit: Also, the new converter is not a GBS8200, some other brand.

Thanks!
 
Last edited:
Positive and negative video syncs

I think I may have found my issue at least. It might be pcb related.

I just got an old oscilloscope to check out the sync signals and they seem to be fine in
terms of their frequency. Red Alert, the game I'm working on has both a horizontal and vertical sync. One thing I noticed was that one of them is a positive sync and the other is a negative. Am I right in saying that they are typically either both positive or negative? If that is true, maybe this is messing with the cga-vga converter.

Maybe this question should be in its own post since its a different topic but I'll put it here too
in case this helps anyone else having cga to vga converter issues.

Thanks.
 
WORLD SERIES uses both negative horizontal and negative vertical sync.
I have tried the resistor in series, one on each sync line with a better but none centered/stabile result.
May consider a different CGA to VGA converter myself at this point. Total aggrivation....
 
WORLD SERIES uses both negative horizontal and negative vertical sync.
I have tried the resistor in series, one on each sync line with a better but none centered/stabile result.
May consider a different CGA to VGA converter myself at this point. Total aggrivation....

Tried converting the negative sync into COMPOSITE sync by using a 7402 IC.

Going to try converting NEG to POS separate sync next by using a 7406 IC.....

No luck......back to the drawing board
 
So I've figured out my issue at least. This may or may not help you. I found out my board also game a composite signal before one of the signals were inverted so both signals were the same orientation. For some reason this wasn't mentioned in the pinout of the manual but I saw it in part of the schematics.

So that composite signal gave me no signal on the GBS-8200 board, but when I used another converter it worked perfectly. So here is the link to the other converter that I bought:

http://retroactivearcade.ca/15k-24k-31k-cga-rgb-to-vga-converter/

It's also made in China like the other one but it seems better to me so far at least. Maybe try buying this one.

Good luck!
 
This converter also solved my problem with World Series. Just Plug N Play !
 

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