G07 Screen Split - how to adjust?

neopolss

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I just recapped a G07 for a Phoenix cab, as well as doing the sync "upgrade." Put it all back in. Picture is fantastic, but I cannot get it to display full screen correctly. Half of it comes to the bottom of the screen. See video:

http://www.youtube.com/watch?v=XaOvQ85WoXU

I couldn't make any pot adjustments worth a darn, so I ordered Bob's pot kit and replaced 'em, no change. B+ measures a steady 120 after 30 minutes of running. Any ideas? I thought I did the sync upgrade proper. Would it cause this? Before the cap kit it would display full screen but the hold wouldn't stay put. There's also a bit of pull or bending midway through the image.

Thanks for your thoughts on this.
 
Post some pics of your chassis (off of the tube and out of the cabinet), including a close up of the sync upgrade.

Did you touch up the solder on the sync headers?
 
When I adjust the horizontal freq. it will jump momentarily to where it should be and then will go right back to how you see it in the video. By momentarily I mean like a blip of a second. I'll try to get a photo of my work on the sync upgrade. It didn't seem like it was overly difficult. Unless I just misread the directions wrong. Anyone have a how-to photo of what it *should* look like?
 
It's pretty simple:

1) Remove C303.

2) Remove C501 and install the cap from C303.

3) Install a 10uf 50v polarized cap in the spot for C303, with the positive leg in the hole closest to the edge of the chassis.


Did you reflow the sync input pins?
 
I did reflow them. But I will pull it and check the other. I don't remember if I soldered the closest hole or not.
 
I did reflow them. But I will pull it and check the other. I don't remember if I soldered the closest hole or not.

One side has two holes on the same trace, so either hole is fine with that leg, as long as it is positive or negative as necessary. The other side has one hole. Just make sure both legs aren't on the same side...
 
I touched up the solder on the sync headers per suggestion, checked and double checked the sync upgrade. It is definitely correct. H adjustment on the pot is super super touchy. I can barely get it to stay even and when I do there's a slight juggle to it. I'm stumped on this one. Any more suggestions? Besides "put a new chassis in it" Where's Ken?
 
Hook that monitor up to your Centipede to see if it's doing the same thing...
 
BTW - what's up with all those big resistors tied together down there by the flyback? The horizontal shift pin is down there. Might want to check to make sure you have the proper resistance for that area, as something way off base might be shifting the image way to the side, although I don't usually see it fold back to the other side...
 
I did notice those resistors but didn't think anything of it. You think it was a change after the fact? This was pulled from Phoenix. Pretty sure it was orginal to the cab. Anyone else seem this type of resistor pairing? I looked at some google photos of g07 chassis and definitely see the difference. What kind of resisitor should be there?
 
Had a chance to pull the chassis out and mess with it again. Removed the kludge of resistors down by the hor. line and replaced it with one to spec. No change though. I have a few observations though that perhaps someone can spur me in a new direction. The V LIN. pot will often create a double image and will make the screen jerk into its proper position, though no amount of adjustment will make it stay put. Once I get the image stable on this pot, I have to adjust the HOR. FREQ. pot since it makes the image skew to one side or the other. The pot is still super touchy though, as I barely touch it and it will veer one way or another. It won't stay put either. If I turn the machine off and then on, the image will be slanted left or right. Any thoughts?
 
Not an issue, as that pin is not connected to anything on the yoke connector...
 
I have another chassis coming and I'm going to swap and see what happens. In the meantime, here's a question. This cab has been sitting for ages. The monitor and everything else is original, so I can eliminate a swapped monitor being an issue, BUT, since this issue was happening BEFORE the cap kit and isn't correcting, is it possible that it is coming from the game pcb itself? And would a bad power supply cause a pcb to supply poor sync? I figure while I wait I might as well check the power supply and inputs. Thoughts?
 
Keeping this thread alive. I put in my happ vision pro monitor yesterday and it displayed perfectly. So that eliminates all other possibilites, although the +12v runs really high at +15.8v. That seems awfully high. On the G07, I have some transistors on order for the sync, I'll save the IC for the next step.
 
Stolen information from Ken Layton:

On many G07 chassis, the factory had mistakenly installed the wrong value resistors in the sync circuit. Double check yours to be sure that these resistors are the correct value:

R314, R317 (the ones most often incorrect)

R303, R306 (sometimes I found these were also wrong)

All of the above resistors are supposed to be 390 ohms, 1/4 watt. The factory had mistakenly used 4.7 k which of course is way off from what's supposed to be there. With these incorrect resistors in there, the sync circuit is too weak causing drift and or curl.
 
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