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MV1-FS Video Jittery

adgenet

adgenet

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Feb 27, 2019
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I just picked up an MV1-FS and found that it exhibits wavy / jittery video up at the top at all times.
The screen also jumps around slightly / a few pixels randomly while playing a cart.

While this is all on the admittedly shitty GBS scaler, I tested on multiple gbs boards, and multiple LCD monitors and they all exhibit the same behavior.
These same gbs boards (running gbscontrol) handle all of my other boards in my tiny collection just fine, so I'd rather not shell out a bunch of cash on a different scaler only to find out it's not the scaler at fault.
Don't have a CRT to test with either.

I traced the sync line with my multimeter from the JAMMA edge all the way back to the NEO-IO chip and it all seems ok, but since I don't have an oscilloscope, I can't check any further than that.
I also tested the 100 ohm and 470ohm resistors that are on the sync line and they are within spec. The board is supplied with exactly 5V off of a high quality supply.

Has anyone has ever seen this issue on an MVS before?
Any thoughts on how to approach troubleshooting this?

Short gif of the issue below:
out.gif
 
Most likely the scaler. MVS has an out of spec sync rate that doesn't play nicely with some equipment.
 
Even same model of boards can have a different sync, I discovered that when i started to play with extron RGB processors. Mv1c for example will always have a sync problem on top screen, you will solve if use a specific sync generator like ISL59885.
 
Thank you all for the input.
I did some reading and was about to try stupid things like replacing the crystal to change the sync and whatnot.
Before I went down the path of stupid, I decided to be smarter and consider rolling back the gbscontrol firmware.
I jumped around going back in time and eventually came across a version from 2019 that works perfectly. Probably should report the issue on the project page.
Everything is perfectly stable. The top shows no distortion, and the screen shifting has stopped completely.

Pics of success:
img0.jpg
 

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adgenet said:
Thank you all for the input.
I did some reading and was about to try stupid things like replacing the crystal to change the sync and whatnot.
Before I went down the path of stupid, I decided to be smarter and consider rolling back the gbscontrol firmware.
I jumped around going back in time and eventually came across a version from 2019 that works perfectly. Probably should report the issue on the project page.
Everything is perfectly stable. The top shows no distortion, and the screen shifting has stopped completely.

Pics of success:
img0.jpg
Click to expand...
What? You can update firmware? How? Tell me more 8o
 
@adgenet
Did this ever get fixed in a newer version of gbscontrol
I am running the latest on my MVS and it is jittery and seems sluggish.
What version works for you on the MVS?
Thanks
 
Looks like 2 days ago on GBS-C bug tracker Rama stated Neo-Geo is still a known issue https://github.com/ramapcsx2/gbs-control/issues/216

I have AES and MVS and neither works properly with GBS-C (distortion at top, and lots of freeze/dropped frames). I haven't tried downgrading the firmware since I also have a Framemeister and the Neo-Geos work fine on that.
 
adgenet said:
Thank you all for the input.
I did some reading and was about to try stupid things like replacing the crystal to change the sync and whatnot.
Before I went down the path of stupid, I decided to be smarter and consider rolling back the gbscontrol firmware.
I jumped around going back in time and eventually came across a version from 2019 that works perfectly. Probably should report the issue on the project page.
Everything is perfectly stable. The top shows no distortion, and the screen shifting has stopped completely.

Pics of success:
img0.jpg
Click to expand...
Hello, I am trying several older firmware versions to fix the same problem but with all versions I have the same problem. With the original firmware the issue does not occur. Can you please share the version you are using?
 
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