Hantarex 9110 very sensitive vertical hold. (SOLVED)

[perjmolsen]

Hi

I need your help

I have a MTC 9110 who has a very sensitive vertical hold.

A small video


I am able to get the picture to lock vertical, but it stays only for a short time, and if i turn the  power off the picture is rolling or has shifted a bit so that it is not longer in center
Trying to solve this issue, i have done:

1. changed nearly all the electrolytic caps, except C24 and C205 (I did not have these in my parts boxes, but the old one tested OK)
2. changed the vertical freq pot (no diffrence)
3. tried to put in a 5k resistor between gnd and vertical sync (no difference at all)


When the picture is not locked vertical i got red lines across the screen, but they disapeer when i get the picture to hold, and become stable.
What can cause my picture to be so sensitive to the vertical hold?

Can it be the IC1 TDA1675A that causes the issue?

The manual for the chassis is found here: http://www.arcade-museum.com/manuals-monitors/Hantarex%20MTC9110%2025in%20and%2028in%20Color%20Monitor.pdf

[perjmolsen]

Hi

Just an update - found an TDA1675A in my parts, and where able to turn off and on the game without the picture rolling.. 
But it is still very very sensitive... so I will keep you updated 

[perjmolsen]

Hi

Just an update

The other day the screen began to roll again 

The all mighty chassis repair guy ->grantspain  told me that only the h-sync needs to be connected.
So i checked my connections.. and also the v-sync where connected...
So removed the v-sync and now the vertical adjustment pot is not sensitive any more and it holds the sync