Pesky G07 won't stop scrolling

Zork2

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Pesky G07 won't stop scrolling, left or right. Won't "lock" into place.
Running chassis in known GOOD Ms Pac cab. So its nothing other than this chassis...
I've read through the threads and here is what has been done.

Full Bob Roberts Deluxe kit, with sync upgrade.....
B+ set to 120V
All new pots
New IC 501
new X301, 302, 305, 306
Re-flowed all the pins where both the sync plugs plug into the chassis.....

What am I missing here? This one is frustrating!
 
Interesting quandary. It seems you have all the bases covered as far as new parts. The flow chart ends at testing X302, X306 and substituting IC 501. If it was me, I'd double check that these were good, even though they are new.
Beyond that, if it were me, it would become a donor chassis.
In some cases, patience is not one of my virtues..
 
Interesting quandary. if it were me, it would become a donor chassis.
This has crossed my mind! HA!
The thing is, the darn picture is PERFECT other than this....
I've read through EVERY KLOV post dealing with the subject, and I've done all the obvious stuff. I pulled all these parts from a known good chassis.... so THEY ARE GOOD, other than IC501 which was a bob purchase and its bad straight from him...(I doubt)
Tested all the resistors in the 300 section...Re-flowed just about everything in the sync section.
Frustrating...
I'm hoping someone has SOMETHING else to try.....
 
You are sure your PCB is good? Had the exact same issue with my G07 (scrolling left to right) and my PCB ended up being the problem...
 
You are sure your PCB is good? Had the exact same issue with my G07 (scrolling left to right) and my PCB ended up being the problem...
PCB is 100% good ! I read through your thread.... ;)
Like I said, its in a Ms Pac that works fine with the 3 other G07 chassis I've put in it....
So I'm assuming its not the PCB, or anything else in the wiring like a broken sync wire in the harness etc.....
 
scrolling is one of the most frustrating things about these chassis. try replacing the pot and make sure you dont have any cracks on your traces in that section, meter each trace point tot point to the end of the circuit.
 
It has new pots all the way around....
I have tested 3 other chassis in that machine and they are all fine...
I have put the defective chassis in 2 other working machines....it scrolled just the same in them...
Only thing I can even think of is I got a bad ic 501??
 
Bump for a new weekend full of more smart people!! Any sugestions here?
All are welcome...ALL ARE WELCOME!
 
I would really be interested to see if this is a sync issue. I had the same problem with a taito chase hq on a G07. Worked fine on most of my other games. messed around with the sync wiring to finally get it to hold. Moved it and have almost the same problem with a Double Dragon 2 PCB. Works fine with Atomic Punk tho. Maybe I should just sell the DD2 and live with it hehe. Good way to find out if it is just the signal from that pcb though. Just food for thought lots with more experience than I here.
 
R314, R317, and the others, all the correct value?

Yep, that's the first thing to check. Some were sent from the factory with 4.7k-ohm resistors instead of the 390-ohm they should be.

Another issue I see sometimes is that it won't stop scrolling with the ground wire on the 6-pin connector, but will with it on the 3-pin connector. Or vice versa. You can try moving it, or just add a jumper on the bottom of the chassis between the two ground pins.

And I assume you've tried a known working chassis in this cab AFTER this chassis and had it work fine? I spent quite a while tracking down a sync issue when it turned out that my test bench video wire and broken INSIDE THE INSULATION from all the times I plugged and unplugged it. A continuity check found the problem...
 
Thanks for the ideas guys, I've been knee deep in a couple restoration projects, and this monitor is further down my list, but I'll check that stuff and post the results in this thread.......
 
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