Extremely Sensitive G07 Horizontal Frequency Adjustment

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Extremely Sensitive G07 Horizontal Frequency Adjustment

I have a G07 that i've recapped, new regulator, new HOT, new adjustment pots (minus B+), new fuses, and new cap kit. I plugged it into my test rig and while the chassis works fine, I cannot get the Horizontal Frequency adjustment fine tuned. I can get it close, but the full picture (Pac Man) will still slowly roll upward/downward depending on which way I adjust the pot. The fine tune is so finite I cannot get the picture to stabilize. I can come very close, but the moment I try to remove my adjustment tool it goes out of adjustment and starts rolling again. When I can get the picture somewhat stabilized, the color, and overall adjustment looks really good.

This chassis is going in a Pac Man, so it has negative sync. Sinc wires are jumped, and everything is wired exactly where it should be. I've checked the infamous "wrong value sync resistors" and they are all in the proper range. I've also swapped out the 5K Horizontal pot for another one, with the same result. B+ is at 122 volts - i'll work on getting it to 120, but I don't think an additional 2 volts would cause this issue.

Any sage like wisdom on this matter would be greatly appreciated!
 
I got the same issue with a G07 in a Pole Position.
New fly back and caps but pots are not new, but look perfect.
Will not hold, keeps rolling no matter how finely you adjust horizontal hold.
Super irritating..
 
I got the same issue with a G07 in a Pole Position.
New fly back and caps but pots are not new, but look perfect.
Will not hold, keeps rolling no matter how finely you adjust horizontal hold.
Super irritating..

You haven't replaced or even tested the pots? I think that would be your next step. I replaced all the pots on a few of these chassis to resolve issues you describe.

The way a pot "looks" means nothing!
 
I have a G07 that i've recapped, new regulator, new HOT, new adjustment pots (minus B+), new fuses, and new cap kit. I plugged it into my test rig and while the chassis works fine, I cannot get the Horizontal Frequency adjustment fine tuned. I can get it close, but the full picture (Pac Man) will still slowly roll upward/downward depending on which way I adjust the pot. The fine tune is so finite I cannot get the picture to stabilize. I can come very close, but the moment I try to remove my adjustment tool it goes out of adjustment and starts rolling again. When I can get the picture somewhat stabilized, the color, and overall adjustment looks really good.

This chassis is going in a Pac Man, so it has negative sync. Sinc wires are jumped, and everything is wired exactly where it should be. I've checked the infamous "wrong value sync resistors" and they are all in the proper range. I've also swapped out the 5K Horizontal pot for another one, with the same result. B+ is at 122 volts - i'll work on getting it to 120, but I don't think an additional 2 volts would cause this issue.

Any sage like wisdom on this matter would be greatly appreciated!


Just out of curiosity have you tried the monitor with any other game?
 
I've tried it in my original Pac Man cabinet in addition to my workbench test rig. Two different monitors, PCB's, wiring harnesses, etc, same exact results.
 
You're not going to like this answer (or maybe you will)... but I've found in the past, that when it's doing this, your sync signal isn't happening. If you can't get it to lock in, it doesn't have sync which is the whole problem. It's not that it won't adjust properly, it's that you have 0 horizontal sync and that's why it keeps rolling... I'll bet if you disconnect that wire it'll behave exactly the same.

So you're losing the sync signal somewhere, and you've already proved it's got to be on the chassis itself since it does it with different pcbs and different cabinets.

So my point is, you don't have an adjustment problem, your horizontal sync is completely gone. Ohm out your wiring through the connector to make sure it's not as simple as the pin, even if it looks fine check it with a meter. Don't just check from the pin to the bottom either, try to check through the connector, so one lead on the game pcb, and one lead on the next resistor on the monitor pcb or something like that.

If that isn't it, look on the schematics and work through the transistors right there at that negative sync connection, I believe there's two on the negative sync section. It's likely just a bad solder joint somehwere, though.
 
I got the same issue with a G07 in a Pole Position.
New fly back and caps but pots are not new, but look perfect.
Will not hold, keeps rolling no matter how finely you adjust horizontal hold.
Super irritating..

On Pole Position, it has a weird way to wire it up. It has the negative and the positive on the connectors, I think there's a little jumper you can unplug to seperate them.

If you plug it into a g07 with the little jumper connected on the sync harness, you're plugging up both the negative and the positive sync and it makes it roll.

Check to see if that's what's going on with yours.
 
After a lot of testing and searching, the problem finally revealed its self. I handed the chassis over to a operator who has a lot more experience in the arcade repair realm, and after a through visual inspection he began to gently press on the components topside. Turns out the resistor at position 529 (just above pin #1 of the IC) was broken, but you couldn't tell just by looking at it. After I replaced the resistor, all was well.
 
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