Vertical hold very sensitive on G07. How to fix?

[Popcorrin]

I have an electrohome G07 and it seems to be in decent shape with a good picture.  The only problem is that it is very hard to get the vertical hold set so the picture doesn't roll.  For instance, I can load a game such as offroad and get the hold set and play for 5 minutes and it will start rolling and it will have to move the v. hold pot ever so slightly to get it to stop.  It is impossible to set the v. hold in a position that it will work for more than one resolution.  Need some advice on how to fix. 
Thanks

FYI, I am using advmame.

[Ken Layton]

Some G07's got out of the factory with the wrong value resistors in the sync circuit.

[TurboC--]

I was just screwing around with / fixing my WG4616 and I noticed the Horizontal Osc. Coil has a MASSIVE effect on getting the picture to stabilize.  But if you decide to mess with it, just remember where it was set to begin with...

[Ken Layton]

One has to remember that back in the "glory days" of video games, American & Canadian manufactured monitors were built to be used with gameboards that output an American standard gameboard sync signals. Japanese built monitors were generally made to sync to Japanese gameboards and bootlog gameboards. Electyrohome and Wells-Gardner monitors of the day expected to see sync (and video) signals within a standardized range. Once JAMMA became a standard then sync signals were required to be more stabile between gameboard manufacturers. Todays monitors do indeed accept a much wider range of signal tolerance.

[Popcorrin]

I was just screwing around with / fixing my WG4616 and I noticed the Horizontal Osc. Coil has a MASSIVE effect on getting the picture to stabilize.

[Popcorrin]

Another strange thing I noticed is that if the overall color the game is displaying changes it will cause the screen to start rolling.  For instance I can set the v hold so that the picture is stable on the title screen of pole position 2 which is a mostly brown screen but when it changes to the track the screen starts to roll.

This has me very baffled and frustrated.

[TurboC--]

Well when the horiz. osc. coil was not set properly, I could get what appeared to be a "stable picture" turning the h and v sync, however the picture was a jumble of nonsense.

[dabone]

Most monitors don't have the horizontal oscillator.


(The only one I've ever dealt with that had one is the 4600 series)


The g07 doesn't have one.


Bob's pages are great for info on the g07.


http://homearcade.org/BBBB/


later,
dabone

[Ken Layton]

Horiz Osc is just another name for horiz frequency or coarse horiz hold.