G07 Screen Split - how to adjust?

[neopolss]

Yeah, I checked 'em already. They are correct. I just replaced the transistors 301, 302, 305, & 306 with no visible change. However, when I started adjusting the pot on the H Freq., if I push the pot in a little here or there, the picture will straighten out for a second. Now, I just changed this pot before and it was acting the same way, but could that be indication that it is not making good contact to the pad or to what it controls? What does that pot adjust? Is it the resistor behind it? If so I will replace it immediately. Or is this driven by the IC?

 

[neopolss]

Anyone? I want to chuck this through the window but I'm determined to see it fixed.

 

[neopolss]

Ok, here's the status update. I have changed out the flyback, recapped, changed vertical and horizontal transistors, changed out IC501, changed the pots, and the horizontal hold still won't lock in (vertical still pulls a little too, but hard to tell with all the scroll). Per another user's suggestion, I swapped this into my missile command command that has a g07, and it does the same thing. So I can officially eliminate wiring as a problem, or poor sync signal. Is it a continuity issue now? I'm thinking resistors. Anyone got a rough idea on where I should look?

 

[Alpha-tron]

Wow you replaced almost everything.

If the Sync Amp section is working maybe it's the c501 capacitor It's between the Sync amp section and the ic501.

It's not a normal major part that causing you issues. I bet it's one of those rarely parts that normally doesn't fail.

IF you had a scope you could probe pins # 1,2 and 3 you should get a 1.5 V ~ 1.4 V peak to peak signal reading. Pin #16 of the IC501 is the input and should give you a peak to peak rating of 12V peak to peak.

If the reading are ok. I would start looking at the Phase detection area.
c505, c504, c503 c506 c507 c508

If I didn't have a scope and I have rocks and sticks to work with. I would use the working G07 as a test bench and slowly start swapping parts.

 

[neopolss]

Ok, so here's where I sit right now. My Phoenix had a G07 with sync issue. Pulled chassis, redid everything, still lack of good sync. Tested the chassis in my Missile Command cab with a G07, same result, lack of sync. This made me think it was the chassis. I placed a Happ vision pro in the phoenix cab, no issues, perfect picture. This again makes me think the issue is the G07 chassis. Frustrated, I bought one from chris on here that's recapped too. SAME ISSUE! The screen won't lock, sometimes there's a slight double image, always pulls to the bottom and snaps back into place. I have no doubt that the chassis from chris works perfect. So now my question is, what's the problem with this game? Phoenix is positive sync correct? I have it looped to so the signal is combined. I have such terrible luck with G07s.

 

[Dokert]

You have a horizontal issue, check the Horizontal width coil and after that chase the h circuit for cracks or cold solder joints. Pay close attention to the area around C302.

 

[neopolss]

I will go over the chassis and look. But man, what are the chances of having TWO G07 chassis with the same problem?

 

[kstillin]

This is odd.

If this was split on the vertical axis, since it's locking in at the halfway point, I'd try swapping the sync pin over to the input for the opposite polarity.

 

[neopolss]

Is there a possibility that there is a problem with the tube/yoke itself and not the chassis rebuilds? Or is it possible that the sync signal is weak? Is there a way to strengthen the signal to test that theory?

 

[neopolss]

Update on this chassis. I have replaced the horizontal width coil and X01, as well as checked/resoldered C302. No change at all. The screen doesn't split like it did before, but it still doesn't lock. Anyone want to take a crack at this thing? I'm about to start offering a reward to the first person who can solve this problem. Oh, I also recapped the Phoenix PCB as well, on the off chance that power/weak caps could produce poor signal. I'm desperate at this point.

 

[LyonsArcade]

Your problem is the sync upgrade doesn't work well with positive sync games, IMHO. I've had probably 5! monitors over the years that had the same damn thing happen that's happening to you. I usually don't do the sync upgrade anymore because of it.

1. I've never seen it fix anything
2. 5 times I've seen it screw up the sync.

Usually though I notice it as soon as I put it back in the cabinet, and can 'undo' the upgrade. You've probably thrown your 'cap' away long ago though, so I would if I were you just put it back how it was, even if you have to reorder the one capacitor from mouser or something.

 

[LyonsArcade]

Let me also add that this is a particular problem with Phoenix, which is a touchy 'sync' game anyways. Out of the 5 I'm saying I had to 'undo' the sync mod on, 2 or 3 of them were Phoenix cabinets.

Think about it. You got it, picture was sync'd, correct? All you did was a capkit and that damn sync mod, now the sync is messed up. I've seen it several times on phoenix and a couple more times on other positive sync games.

BTW Ken is also right about some of these having the wrong resistors in them. That's not your problem because you checked it, but that is the problem sometimes.

 

[neopolss]

It's worth a shot. Thanks!

 

[neopolss]

What's the value of C303? Since I need to order the cap for C501, might as well get a fresh one to put back in C303. The schematic just has .1 MY

I don't know what that means.

 

[neopolss]

I undid the sync mod but no perfect picture yet. The good news is that there doesn't appear to be any foldover anymore. The bad news is that I still can't lock in a hold. I have the H pot turned far right, the V hold pot is far left. I started with them centered. It looks like the picture is at least straight now, with no pull or stretching (I had this U shape picture before), but the sync is just ungodly touchy. Any tips? Is there a way to boost the sync signal input? It's hard to tell from all the scrolling, but it appears that H hold still isn't locking, a V hold still slightly drifts.

 

[LyonsArcade]

I've seen sync modified by people adding resistors between the sync pins and the ground pin, but I don't know what the values would be or anything...

 

[neopolss]

I've seen that too, but it's beyond my level of understanding as to the value or how it's determined. Anyone else have some input on this?

 

[neopolss]

Ok, who can I send this to? I've pretty much done every normal operation to it, so I need someone who can probe this thing and tell me whats wrong without hurting my wallet too much more. It's beyond my level of expertise. I think I have at least $70 in this thing in parts, if I can get it fixed it will be the best G07 chassis out there, since it is practically new. Can anyone help me out?

 

[Shupac]

I just fixed a G07 with exactly the same split screen problem. The problem turned out to be a shorted Zener D505.