I’m happy to say we can finally put this particular G07 chassis work to bed. As it so happens I could’ve been done with this repair weeks ago, but therein is the “learning” —as they say. Part 1 of this post broke down the issue with the G07 and the various musical chairs played with chassis across games. Part of the reason for these posts is establishing provenance for various parts given that will all be quickly forgotten as I endlessly swap out parts for testing, etc.
Yoke connector on a G07 CBO
Turns out the fix was staring me in the face all along. The yoke connector I added (in addition to changing the T503 transformer) was what was causing the horizontal collapse.
Condor’s Horizontal Collapse
Keep in mind the monitor was working when I swapped the T503 transformer to deal with the hissing, and in all my wisdom I decided to add the gray plastic yoke connector (pictured above) as part of a general clean-up.* Turns out one of the horizontal pins was getting pushed up whenever the yoke connector was installed and that was responsible for the collapse. Really?! I feel dumb and wasted more time than I care to admit, but there you have it.
I figured this out because I have another game with a G07 in my basement (Bagman), and on an informed lark† I swapped the “broken” chassis and it was working. I immediately felt equal parts elation and frustration. I also noticed there was no hiss so the transformer swap worked—the original reason I did all this work. Seeing it working meant the issue had to be the yoke connector, and after closer inspection and testing it was just that.
I brought the chassis into bava.studio and tried it in Robotron—it’s original home before starting this process. After some yoke adjustments, it worked there as well. No surprise, but the additional test was necessary because Bagman has a separated vertical and horizontal sync video input that was making the image roll. To ensure there wasn’t an issue with caps on the newly working chassis (bad caps can also make the image roll), I wanted to try it on Robotron, which has both horizontal and vertical sync on the same connector.
Some unsolicited advice, always test your “broken” chassis on another machine if possible. More unsolicited advice, make one change at a time. Changing the transformer and yoke at once killed me here.
Condor looking mighty fine.
I left the chassis that I did all this work on at bava.studio, and brought the Robotron chassis back home and installed it in Condor. It was like a new day in the bavacrypt. I had been working on this on-and-off for more than a month, so having this solved and the arcade fully operational was beautiful.
I’m thrilled to finally put this fix to sleep. A silver lining here is that all the parts are on order to entirely rebuild my donor G07 chassis that I scavenged during this repair. It would be really nice to have learned enough to have a fully work spare on-hand given so many of my cabinets use a G07 chassis because, like all things, sooner or later they’re gonna go.
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*If you mess up the order of the yoke wires you can cause real damage to the chassis, so these plastic yoke connectors are keyed to ensure you install them properly. Often times you’ll find the yoke wires connected separately, and if you don’t know the order or mix up the gray and white wires you could have issues. So, to my defense, I was at least doing it for good, even if it screwed me.
†Several comments on KLOV noting horizontal collapse was very rare on the G07 chassis pushed me to swap the chassis into Bagman. While vertical collapse was fairly common as issues go, the fact that horizontal collapse was not forced me to rethink all the testing I was doing to the horizontal width coil, HOT, various resistors, etc. and just re-examine the yoke—one easy way to do that was trying a yoke connector on another chassis.
