trashedcabs
Student
Bought a bulk lot of these sanwa chassis. I have two chassis which both work but both exhibit a vertically twitchy and noisy picture. One of them also has the pincushion/size issue which is common on these with bad flybacks, but I have swapped the flyback with one from a 100% known good, low hour chassis and it still exhibits the issue.
I have done a little bit of work on the chassis so far. This first chassis had a completely bad flyback (cracked and made terrible noises). Replaced with one from another chassis and it was working but squealing. There were some bulging caps, so I did a full cap kit and it fixed the squeal. I had raster but no video and found diode D415 in the ACL circuit open, and replacing it restored video.
The picture started going very wide and had crazy pincushion which I read is a symptom of flyback failure. I replaced the flyback and it fixed the width temporarily, but the noise and twitching remained. The games were on for a few days at an event and when they returned to the shop, the image had gone wide again. I swapped the flyback with one from a 100% good, known working chassis and the width was still a problem.
The old flyback works fine in a known good chassis, so it is definitely not the issue in this case.
All the polymer caps on the chassis test good. I've checked all the main components--HOT, diode D401, all the mosfets on heatsinks, I'm suspecting something in the power supply, considering it appears to be affecting both deflection and HV.
Anyone else dealt with this? Figured I'd do some crowdsourcing before diving way into it.
I have done a little bit of work on the chassis so far. This first chassis had a completely bad flyback (cracked and made terrible noises). Replaced with one from another chassis and it was working but squealing. There were some bulging caps, so I did a full cap kit and it fixed the squeal. I had raster but no video and found diode D415 in the ACL circuit open, and replacing it restored video.
The picture started going very wide and had crazy pincushion which I read is a symptom of flyback failure. I replaced the flyback and it fixed the width temporarily, but the noise and twitching remained. The games were on for a few days at an event and when they returned to the shop, the image had gone wide again. I swapped the flyback with one from a 100% good, known working chassis and the width was still a problem.
The old flyback works fine in a known good chassis, so it is definitely not the issue in this case.
All the polymer caps on the chassis test good. I've checked all the main components--HOT, diode D401, all the mosfets on heatsinks, I'm suspecting something in the power supply, considering it appears to be affecting both deflection and HV.
Anyone else dealt with this? Figured I'd do some crowdsourcing before diving way into it.
