Hantarex 9110 very sensitive vertical sync.

[ZMB]

I have replaced all of the caps on a couple of my Hantarex 9110's and even though the picture is great...the sync on both are so very sensitive that the slightest touch on the trim pot for the vertical sync will cause the roll. I was wondering what else I could look for as all electrolitic caps have been replaced.

[grantspain]

what is the video source,jamma or pc?
and which pin of the input plug do you have the sync connected

[ZMB]

Jamma off of a Neo Geo. The sync is on connector CB1 if I am remembering right. The ground is on CB3 as well.

[grantspain]

neo geo is snk,hantarex tend to prefer the vertical and horizonyal sync linked with snk
another thing to try is connecting a 5k resistor from the vertical sync to the video ground

[ZMB]

First let me thank you for your help. I am grateful. Secondly, I have tried that and after about a half hour or so when the chassis board heats up it will start to roll. Then it will sync again. And then it will roll again. Over and over. What in the Vertical section when heated up will cause the Vertical sync to go weak?

[grantspain]

there are a few components that can cause this,use this schem
http://www.freeinfosociety.com/electronics/schemview.php?id=2245
although its a mtc9000 it should be identical

check the transistors on the sync circuits and check the voltage +12 at TP12

[ZMB]

I replaced all the trannies in the vertical circuit and check all of the resistors...All seems good but still will start to roll after an hour or so. Is there any chance that it could be IC2?

oh yeah...

the twelve meters out around 12.27 vdc

[grantspain]

12.27 is good,after 1 hour points towards a heat related problem pointing to component failure-very unlikely cap as normally its the opposite affect
ic2 is the next option,it could be breaking down internally
bugger of a fault though

[qrz]

the tda2595 is likely the culprit .
looking at the ic mfg's spec ( www.alldatasheet.com) suggests an instability in either h/v processor will affect the sync lock on the other. ( my opinion )

qrz