2 games with vertical hold problems

[redfivexw]

Hi,
i have two games, one is a nintendo dkjr with the sanyo monitor, the other is a millipede with a wiya replacement chassis.  Both games have a hard time holding vertical hold.  The control is very touchy and even when you get it to stay, when you shut the games off and on again they start to roll.  I rebuilt the sanyo monitor, new caps.  The wi-ya chassis is brand new.  I am wondering if it is possible for the game boards to be defective and cause this?  Other than the picture rolling, they both have a good picture.

[gokun]

generally the boards themselves don't cause this; generally it's a bad signal, etc. so I would probably start checking the basics like the harness to the board and the monitor plug(checking the sync line(s) specifically)...
I have one particularly that takes about 5-10 min to warm up....until it's warm it rolls, and if you adjust it prior to that it will roll once it warms up...something to think about if your symptoms are similar...
as always however, the regs here will probably have better info for ya...just trying to help out in the meantime.

[grantspain]

i have done a mod a few times for this problem by linking a 5k resistor from the vertical sync to the video ground

[redfivexw]

Yes,
my millipede does exactly that, it rolls for about 5 minutes, then once warm it works fine, but you have to tune the picture to the center.  The Donkey kong will stay if you adjust it, but it always rolls when you shut it off and turn it on.  Pain in the ass.  Like i said, both monitors are rebuilt or new.  I am interested in the workaround however, can i get  more info on that?  I will check my wiring, but everything seems to be in good repair.