GO7 not holding Horiz

ToplessZ

Well-known member

Donor 11 years: 2011, 2013-2022
Joined
Oct 25, 2006
Messages
1,652
Reaction score
27
Location
Claremore, Oklahoma
I "had" and fully working GO7 monitor. I was converting the machine into a different game and had the monitor installed while I was drilling away at the metal control panel. After I was done I turned the game on and it has a slow horiz roll to it now. So I resoldered just about every joint on the thing and I also replaced all the pots with no luck. I can get the picture to stop rolling with a small pot adjustment, but as soon as it changes screens it looses the hold and starts rolling again. What the hell happened???
 
It sounds like you need to recap the machine, or it is possibly a problem with the pot.

I guess it is also possible that you have some metal filings somewhere causing problems in the hold circuit... I have seen metal filings cause ghost grounds and other shorts that were nearly impossible to isolate.
 
I've had a problem with G07s lately doing the exact same thing. Sometimes it's the board itself that does it (Capcom Bowl comes to mind) or sometimes I need to hook a connector to both the -H and -V sync connectors, instead of just one.
 
Always check:

Fresh electrolytic caps installed.

B+ voltage set to correct voltage.

Resistors in sync circuit checked to be sure correct ones were installed from factory.

Sync hooked up correctly.

Horiz hold pot good?
 
And I was just about to scold him for not using Google!

Here is what I found using the Google machine-


Ken Layton's post on the subject from 2004:

On some G07's the factory has mistakenly inserted the wrong value resistors at locations R314 and R317. They both are supposed to be 390 ohms, but the factory stuffed in 4.7 k resistors instead. Both these resistors are in the sync circuit. Check for this factory error first before you change any transistors.

Most G07's also need to have the negative vert sync and neg horiz sync jumpered together for proper operation.
 
The chassis was recently capped and working fine for many hours(months), it was even working perfectly minutes before I started drilling at the machine. So its gotta be something knocked loose, which is why I resoldered everything, and I replaced ALL the pots and it still does the same exact thing, so im pretty sure the pots are okay. The video cable is also connected properly so im stuck.....

There are some tiny metallic shavings that seem to be magnatized to one of the components, its not a cap, but it looks kinda likes one, I'll have to get a parts list and figure out what part it is. I thinks is power related though.
 
Ill have to research the correct voltage unless you know it and where to test? I seem to remember that you test Go7 at the large white cement resistor? The B+ adjustment pot is still glued though.
 
I'm bumping this ancient thread just to thank Ken Layton.
I had a G07 that was giving me trouble, and found that it had a 4.7k Ohm resistor in R317 (R314 right next to it was the correct 390 Ohm).
It wouldn't lock on to the vertical sync (always a slow roll). I also did the sync mod (I do that on every G07 I pull out), but I believe that just affects the horizontal. Monitor is solid now.

Ken Layton's post on the subject from 2004:

On some G07's the factory has mistakenly inserted the wrong value resistors at locations R314 and R317. They both are supposed to be 390 ohms, but the factory stuffed in 4.7 k resistors instead. Both these resistors are in the sync circuit. Check for this factory error first before you change any transistors.
 
Back
Top Bottom