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MS-2931 Occasional click (high voltage arc?) and screen pulsing

notsonic

notsonic

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I have an MS-2931 that's been sitting unused in my basement for at least 10 years. I decided to put it in my Astro City while I wait for my MS8 to get repaired and am having some problems with it. (Just to be clear it's the whole monitor (tube+chassis) that I swapped, not just the 2931 chassis on the MS8 tube, if that would even work.)

Every 10-30 seconds, more frequently on cold start, it will click and the picture will pulse larger with the click.
It's also got the black goo leak on the chassis.

My first guess is maybe the flyback is arcing internally, but I have no idea.

Picture looks perfect otherwise. And as I've been writing this post it seems to have stopped clicking.

Edit: it didn't stop clicking.
 
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I had the same thing before with a MS2930 and it was the flyback on its way out
 
Were you able to repair it?

It seems like the only replacements I'm finding are this eBay listing https://www.ebay.com/itm/224974839915 which says "NOTICE: READ CAREFULLY
THE FLYBACKS ARE COMPATIBLE, BUT WILL NOT BE LIKE THE ORIGINAL.
UNFORTUNATE THEY ARE THE ONLY ONES THAT CAN BE FOUND ON THE MARKET
(SLIGHT DIFFERENCES IN QUALITY AND DIFFERENT FORMAT)" and I don't know what that means.

And this one https://m.yoycart.com/Product/21303268145/Color_monitor_ignition_coil_MSU1FUS11 which totally seems like a legit place to put my credit card number.
 
I was not able to repair mine unfortunately. Reviews are pretty negative on those reproduction flybacks from what I’ve seen here.
 
Well I've got bad news and worse news.

First, this monitor is actually the original from my Bass Fishing Blast City, not the Naomi Uni prototype. It would seem that I stole that monitor and put it in my Blast. The tube has INSANE burn in. On a white background, the burn in is actually multicolored. I've never seen that before.

Moving on, I bought a chassis from Yahoo auctions. It doesn't work. The neck board was cracked and repaired, but otherwise a quick visual inspection seems fine. It immediately clicks into a shutdown mode, the one that takes a while to unclick after you turn it off.

So I then decided to install the ebay flyback on my otherwise good original chassis. It does work, as in I get a clean stable picture with nothing sketch about it. But the image is too big horizontally and vertically. This has more or less been the results I could find from other threads. So unless there's some secret adjustment or component to replace, consider the ebay flybacks useless. Sure you get a picture but it's like 10% over-scanned. I'm going to contact the seller and see if he has any suggestions considering he's a repair guy and supplier, but I imagine this is what "SLIGHT DIFFERENCES IN QUALITY" really means.

Here's some pics. Metal Slug is 15khz and KoF Neo Wave is 31khz. Both are adjusted to minimum H and V size. On the MVS crosshatch test you can't see the blue area at all or the box it's in. Similarly on the Atomiswave crosshatch you cant see even the box the red dotted line is in.
PXL_20221027_231631189.jpg PXL_20221027_232723391.jpg

I'm gonna try to swap in the flyback from the new bad chassis and see how that works. I just have to fix my stupid desoldering gun first.
 
I think there is a special menu you can get to on the 2931 with two buttons held down. I forget, but i'm sure you can google it up. maybe it's an operator menu or system menu? factory menu? test? debug? there's different names for the same thing!
 
There’s a thread about those Chinese flybacks on this forum somewhere. If I recall you need to dial in the HV pot to get the correct horizontal size but do not quote me on that. Honestly you should just use the dead chassis flyback and hope it works. Those Chinese flybacks are terrible.
 
I swapped in the flyback from the dead chassis and it seems like so far so good.

It worked in 31khz no problem. When I switched to 15khz I couldn't get anything. Then I couldn't get 31khz either. I tried 31khz through both connections since I was testing with an Atomiswave. I switched back to an MVS and it didn't work, but then I turned it off and on real quick out of frustration and it just worked. I turned it off once since then and back on with the MVS and it seems solid. The whole time it did not seem to be shutting down and sounded like it was making the normal sounds like the tube should be alive.

That said, it definitely made some questionable sparky noises a few times. I was afraid I was experiencing a chassis breaking the tube neck situation, but it seems like so far so good.

Also the off center focus with the real flyback is so much better than the chinese flyback.

tl;dr: swapped the flyback again to a real one and it seems to be working after some weird no picture behavior.
 
had the same thing happen to me, replacing the flyback with a knockoff fixed my issues
 
snakeGrave said:
https://www.arcade-projects.com/threads/ms2931-screen-randomly-expands.13553/

Had to jog my memory but oh yeah looks like in post #8 in the thread I link to above I seem to address that issue by adjusting the h-drive a little bit. This monitor is still chugging along nicely for me with the knockoff flyback and also with the adjustment being made.
Click to expand...
I might have to try the knockoff flyback again. I'm not able to get the replacement old flyback to produce a picture in 15khz. If i turn the monitor off and on real quick i get a picture for a split second that fades out and "zooms" in. Something is fucked.
 
I also used a repro flyback and adjusting the pot allowed for the size to fit correctly. I've not run it a lot of hours but it seemed very solid whenever it has been turned on.
 
I put the knockoff flyback in and it's reliable. I'm not getting any of the shutdown behavior I was getting with the new old flyback.

The problem is it's still way too wide and tall. If I adjust the H drive it does get narrower, but it adds a bunch of geometry problems and I get a bright vertical line down the center of the screen like the image is overlapping. The H drive is the right one, on the back right between the two neck board connectors, right?

PXL_20221028_040751060.jpg
 
I found HV Adj which is one of the 3 pots near the flyback. Other than being one of the scarier things I've done in life, cranking it almost all the way counter clockwise has made the picture smaller than the full screen at minimum size. Geometry (at least linearity) seems fine. I adjusted the spherical? adjustment in the service menu and it looks fine. So unless I'm melting my brain with x-rays or something by fucking with the high voltage, this seems to be working fine. I'll post pics once I get it in the cab.
 
My phone takes the shittiest CRT pictures. Anyway, it looks great and I can finally use my Astro again while I wait for its MS8 chassis to get repaired. I actually like the idea of having a tri sync but the bezel gap with this tube is kind of ridiculous.

PXL_20221028_051333595.jpg PXL_20221028_051339822.jpg PXL_20221028_051409812.jpg
 
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Just want to comment and say thats the best picture I've seen on those Chinese flybacks. Nice work!

Thank you for your detailed posts! 😎
 
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