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

[cperro]

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:



As you can see there is a good amount of horizontal scrolling and jitter, occasionally there is no signal to the gbs-8200 as well as seen in the video. I am guessing this is due to me
putting the horizontal and vertical sync wires together for the gbs-8200.  Would this be correct?  If so, is there a simple way I can get around this while still using an lcd monitor?
Currently I do not have an arcade monitor, I was thinking about purchasing the 19" Vision pro LCD at some point but I wanted to wait to make sure there was not some
significant issue with the pcb.  My other question is could this be a pcb issue or partly due to an issue with the pcb?

Sorry about all the questions, I'm new to dealing with arcade monitors and this is also only the 2nd arcade pcb I've dealt with.

If anyone has any other suggestions for testing out the pcb that would be great as well.

Thanks!

[lilshawn]

most of the GBS-8200 units for sale are chinese copies of copies of copies of....

they used to be pretty good, but seem to be getting worse and worse.

as for the sync, try pressing the "down" button to try and auto adjust the image.

if you have both horizontal and vertical sync, the GBS8200 supports separates sync. you should be able to input the video into the connector by the VGA input (8 pin connector P11) using the supplied wire harness (red/green/blue/black/yellow/gray)

V. Sync to Yellow Wire
H.Sync to Gray Wire

if the sync is still no go, remove the gray wire and move it one slot over next to the yellow wire and try it again.

[cperro]

Thanks for the reply. 

Ya I think you may be right about them getting worse, I bought one several years ago for another arcade cabinet and it worked perfectly and still does.  Or maybe I got a lemon. 

I tried the input with the H and V sync previously and it seemed even more distorted than it is now when I use the cga input.  I just tried it again and for some reason
it just gives me no signal or green screen.  I'll have to see what's going since it "worked" earlier but I don't have high expectations since it was worse than what I am getting now.
The only difference is that I used both grounds last time but only the one in the harness this time, I'll try both again and let you know what happens.

In the manual it states that RGBHV connection (harness) only works with ~30kHz, would that affect this since cga is usually ~15 kHz?   In my other cabinet (ms pacman bootleg) I used
the RGBHV harness (only needed V sync) and it worked fine so maybe it doesn't matter, or maybe it's not a good manual.
EDIT:  I think I was wrong about the ~30 kHz, that may be for the vga input.

Pressing the auto/down button never did anything either. 

Any other ideas? 

Thanks

[cperro]

For some reason I can't get the rgbhv harness to work anymore, so no progress at the moment.  I was wondering if there were any other
brands of cga to vga converters that may be better than the GBS ones.  Or is there anywhere that I could get older revisions of the GBS
converters?

If anyone has any other ideas for hooking up the pcb to a monitor that would be great.  Buying something like the vision pro 19inch would
not be preferred at the moment since it is pretty expensive, especially to get it to Canada.  I tried finding an old crt cga monitor, but I haven't
had any luck.

Thanks!

[cperro]

To update everyone, I found another cga converter which produced a similar but different result, shown below in youtube video:



It's clearer but not syncing properly still.  I recently got an oscilloscope to test the horizontal and vertical syncs.  The frequency of the
signal looks fine but I did notice that one signal was positive and the other was negative.  So I was wondering if this could be
giving the issue that I'm seeing with the cga converters?  I always thought it was typically either positive or negative for both syncs.
Is this correct?

Thanks!