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PSA: MS293X, faulty chassis can break the tube

Anselmo said:
Examining this little board on the 2931 that blew my tube and I see this.....


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motherfucker!
 
Here's my horror story , this one had fireworks coming out of the yoke :)

Also, i did raise the idea of the daughter board with Jomac recently, he said he'd heard this theory before but wasn't convinced. He mentioned with these the Flyback fails, causing the voltage to quickly increase which can neck the tube and also damage all manner of electronics from the lightning zapping everywhere
 

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Molehill said:
Here's my horror story , this one had fireworks coming out of the yoke :)

Also, i did raise the idea of the daughter board with Jomac recently, he said he'd heard this theory before but wasn't convinced. He mentioned with these the Flyback fails, causing the voltage to quickly increase which can neck the tube and also damage all manner of electronics from the lightning zapping everywhere
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That looks violent! What Chassis was this? 2931 or 2930?
 
An operator in Kyoto showed me a video of one of his MS-2933 models showing some serious HV regulation issues. In the video, the screen would slowly contract to like 3/4 its size (from HV rising) and then snap back to what it should be. Then, after a bit, HV cutoff kicked in, and the screen faded out and grew larger (which is typical in that scenario). I'm not so sure any more the MS-2933 different flyback and driver are necessarily an enormous advantage.
 
Hatsune Mike said:
An operator in Kyoto showed me a video of one of his MS-2933 models showing some serious HV regulation issues. In the video, the screen would slowly contract to like 3/4 its size (from HV rising) and then snap back to what it should be. Then, after a bit, HV cutoff kicked in, and the screen faded out and grew larger (which is typical in that scenario). I'm not so sure any more the MS-2933 different flyback and driver are necessarily an enormous advantage.
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Interesting. My 2931 does that first bit about once every 15 minutes, but it’s in flash and not slowly.
 
Hatsune Mike said:
An operator in Kyoto showed me a video of one of his MS-2933 models showing some serious HV regulation issues. In the video, the screen would slowly contract to like 3/4 its size (from HV rising) and then snap back to what it should be. Then, after a bit, HV cutoff kicked in, and the screen faded out and grew larger (which is typical in that scenario). I'm not so sure any more the MS-2933 different flyback and driver are necessarily an enormous advantage.
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I have this issue on a 2930. It’s been fully serviced too. This issue only comes up on cps1 games. Anything else, no issue. The main offender is Daimakaimura. I’ve tried different pcbs and resolutions and the issue never replicates unless it’s cps1.
 
One of my 2930's will sometimes start up with an image at 75% of the screen , and after a minute or so it seems to expand to normal size and stays that way. Ive noticed it happen after days or weeks of non use. Is that the HV ?
 
Hatsune Mike said:
Shrinking is risky business. That means a rise in high voltage, which is alarming because the conclusion is unpleasant.
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I’m not sure where to start looking since it’s so random; these chassis are a real bastard to troubleshoot. I’ll pull it this weekend and see if I can find anything out of the ordinary.
 
Update on my chassis, I replaced the capacitors that had ripped off the pads with the proper SMD caps. I also sourced a new tube, but have been hesitating for fear it will wreck the new tube. Yesterday on a whim I said f* it and tried it and I was able to get it to work. I didn't stress test it or anything, just confirmed it did not immediately kill the tube and left it on for about 2-3 minutes. I guess it works now, I'll dial in the color adjustments over the weekend and keep my fingers cross the chassis behaves.
 

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Yea, I was pretty nervous. Still am honestly, after it cracked my tube i feel like I'm playing Russian roulette every time i turn on my blast cities
 
I went over mine and I found a lot, and I mean a lot of bad joints in the power section and on the flyback. Even if yours is still working fine, it might not be a bad idea to inspect it. It took some time but I went over the whole chassis and reworked everything with new solder.
 
Molehill said:
Here's my horror story , this one had fireworks coming out of the yoke :)

Also, i did raise the idea of the daughter board with Jomac recently, he said he'd heard this theory before but wasn't convinced. He mentioned with these the Flyback fails, causing the voltage to quickly increase which can neck the tube and also damage all manner of electronics from the lightning zapping everywhere
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This happen to me with an MS2931. While playing mushi futari stage 3, the monitor would click turn off and turn back on during a specific spot in the stage. Picture size changed from big to normal. The Chassis did not go into HV shutdown and tube turnt off. I immediately turned the cab off after hearing some weird noises. All went silent and all of a sudden, I could hear a heez coming from the back of the cab. Took the service door off and I could see the yoke slightly leaning. I was super upset. It was game over. Sent the Chassis to Las Vegas and it was confirmed that the flyback was bad. 😞 It was the stuff of nightmares. Chassis was fully serviced, video proof was sent to me that the chassis is working but now I have some PTSD from the experience. Just sharing.
 
PTSD indeed. That's interesting that you saw it kinda go down in real time. How much time elapsed between the picture changing size and the tube turning itself off?

What was the service history of the chassis prior to that?
 
This happened about a year ago. I only had the cab for a year before this incident. I was told that all components on the Chassis were all original by SI. It happened immediately after the tube clicking and changing sizes in picture. From what I recall, the chassis did behave this way on a prior gaming session. SI told me that the flyback was the culprit. They even called me to share the details. This was a bit hard to post. I know that every case is different but if anyone sees something like this happening to their Blast, there could be a bigger underlying concern that needs attention.
 
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