J-PAC Sync Problem....

[Jollywest]

Anyone else have a similar problem with this setup;
AVGA
J-PAC
Hantarex Polo 1 20"

Self-test led shows no wiring problem but no sync in or sync ok led light at all.
No split screen on boot (jumpers on 15 and 31 khz).
Decent picture at multiple resolutions, ranging from 320 x 240 to 800 x 600 but all have vertical roll, that v.freq pot isn't fixing.
 

[Kokapetl]

Can you confirm that the v-freq pot is working? Is this an old problem or did it just begin happening all of a sudden?
The pots on monitors tend to not be of great quality and they wear out quickly, they're more designed to be set-and-leave rather than continually adjusted.

I had a strange problem with my J-PAC where there was some vertical-hold distortion and the display looked dark and flashed brightly every so often (the yellow light on the J-PAC was also flickering on and off).
I still don't know what causes it (it only happens some of the time) but I am able to fix it by disconnecting the J-PAC's USB connection to PC and then plugging it back in again.

[Jollywest]

Thanks for the reply.
It was a working jamma cab when I got it and vertical sync worked fine, although the picture quality was poor.
After some help from   Grantspain on here, I needed a different monitor chassis. Once that was fitted everything worked great.
The problems arose when I converted the cab to mame, when trying to interface the pc to monitor with the J-PAC and A-VGA.
Anyhow, I emailed Andy from ultimarc and it looks like the J-PAC may be faulty.