I'm the proud owner of a X68000 XVI, which is working perfectly fine. But being tired to be limited to 31Khz games, I got an chinese converter board called GBS 8220 which have kind of VGA input with two vga output, was expecting it to convert directly 15Khz to 31Khz Vsync as per its manual/specs, I plug everything together: X68000->vga cable->GBS 8220 input-> vga cable-> my lcd vga monitor....Switch on everything, got the converter menu on my vga lcd screen, but nothing from the X68000 (lcd screen says no input) played with the converter menus and check everything again same. Well connect back the X68000 direct to the lcd screen, no picture!! monitor was switching on/off/on/off damn, this thing killed something!!
dismantle the X68000 mobo and rgb out and after troubleshooting I figured out that pin 2 on the SN74ALS05AN have a bad output (both Hsync and Vsync signals go directly to the SN74ALS05AN from RGB output pin 14 and 15), it is a HEX INVERTERS WITH OPEN-COLLECTOR OUTPUTS, it is located next to the white onboard RGB connector and there is only one type of this component out of the entire mobo so you can't miss it!!!.
Bought 5 of them and at the same time a 14 pins DIP round pin socket
, removed old component from mobo solder the 14 pin DIP socket (in case if something happen again easier to change out!! hope no!!
), put brand new SN74ALS05AN, put back everything together and tadaaa picture was back on my lcd screen!! I was so happy!!
This is just to share my experience with you guys as I saw other people had a similar issue with connecting some LCD TV and having lost their RGB output.
Sorry didn't took any pictures but these below will help you.