Losing sync when strobing/white screen

[gabrielBitts]

Hey folks, I'm havin some issues related to sync when using the GBS-C on PS1, PS2 and Saturn. For some reason, it keeps losing sync when there are strobing white screens. I've tried every configuration on the GBS-C config, but it doesn't solved the issues at all. Here's my GBS config: and here's the video showing the issue: https://user-images.githubusercontent.com/35460886/227976102-119a1dee-94d6-4d4f-b8f9-8f1194d6ad51.mp4

All the consoles that I mentioned I'm running directly from RGB to the GBS and the cables schematics are here: https://members.optusnet.com.au/eviltim/gamescart/gamescart.htm

PS: All consoles are NTSC

[YoImLee]

I've experienced this with some of my systems in the past, the fix is to either use a sync stripper or replace capacitors C33 and C35 with 1nF parts. It was mostly fixed in the firmware, but it can still happen on occasion.

See the documentation about it here: https://ramapcsx2.github.io/gbs-control/Wiki/Sync-on-Green-Capacitor-Replacements.html

[Dr-Wily]

Same problem here, fighting game are unplayable on Saturn. Each time the screen flash there is a lose of sync + there is some strange woble effects on the left and right borders of the image. I have a ODV GBS-C.

[4lexei]

Watching the OP's video, I have only noticed this type of error when the signals were stronger than what GBS supports (that happened to me when I built my first GBS). Do you have the 100ohm resistor installed between SYNC and GND?

Same problem here, fighting game are unplayable on Saturn. Each time the screen flash there is a lose of sync + there is some strange woble effects on the left and right borders of the image. I have a ODV GBS-C.

@Dr-Wily Can you name some games? I could try them, but keep in mind that right now I have an LM1881 installed.

EDIT: Now I have seen what the ODV GBS-C is, I did not know it. Is the vendor or manufacturer not offering support? Most of us have built the GBS following Rama's instructions, therefore our units are all the same or very similar. But when it comes to Chinese-built motherboards, it's sometimes difficult to know how they're built :/

[ramapcsx2]

Hey, a sync loss on white image content is almost always a sign you need to replace the SoG caps. Alternative sync separation will also work, but this is overal the fastest way to fix this: https://github.com/ramapcsx2/gbs-control/wiki/Sync-on-Green-Capacitor-Replacements

[Dr-Wily]

Put a 680 ohm resistor between sync and GND fix the sync loss. Game concerned are SF Zero 3, XMen VS SF, Bomberman and some others.

@ramapcsx2 I read this is depreciated mod, the GBS-C I own is this one :

[ramapcsx2]

Nice board! It's likely that they fixed the wrong SoG capacitor value on these, and then yea, try the 680 ohm resistor between sync and GND option. I forgot about that. Sometimes this is what's needed :)

[andersonmds]

Dr-Wily

Hello friend, can you help me? I have ODV-GBSC 2022.06.20 v2. I am experiencing loss of sync (screen turns on and off). Could you tell me by marking in the photo which resistor to replace? where is the gnd and sync.

I checked from your photo that yours has 5v and 3.3v capacitors, mine doesn't. do I need to put it? What is the value of these capacitors?

Could you tell me about all the components that were replaced? I'm worried because I can't buy another gbs-c. I live in Brazil and here they invented a 92% tax. I can't buy another one, just fix it.

I hope you can help me. thanks!

[andersonmds]

[andersonmds]

[Dr-Wily]

@andersonmds You can just put a 100 ohm resistor on sync signal (csync ou composite vidéo). No need to mod the GBS-C.

[andersonmds]

@Dr-Wily. Hello, sorry for the delay in responding. I replaced the LM1881 chip with another one, bought the LM1881M and the problem was solved. The delay in responding was because I waited for the welding equipment, and to test the odv gbs-c to be sure. There was no need to add the resistor because I already had the 100ohm one.

[andersonmds]

@Dr-Wily I hope it helps me. What is the value of the 5v and 3.3v capacitor that is in your ODV? Take a photo or tell me please.

[Dr-Wily]

Hello,

For me adding a resistor on the scart sync signal solve the issue. But you solution with the LM1881M seem to be good. For capacitors :

• The 5v is 470µF 16v
• The 3,3v is at the same values (470µF 16v).

Hope this help

[andersonmds]

@Dr-Wily

thanks!