29" Makvision monitor shutdown and leaking capacitors?

[mamenewb100]

So I feel a little depressed and stupid for possibly damaging more components on my monitor than I should have. Hoping I didn't make it irreparable.

From the beginning... Even being 'Brand New' I've always noticed some issues with my Makvision 29 inch SVGA arcade monitor. And I was aware from the beginning that many people reported issues and warned it was cheaply made yadada. I still took the chance 4-5 years ago because I wanted a true arcade monitor that wasn't already used.

Games displayed fine and looked fairly nice for the most part. Especially after finding out I could double the refresh rate of 15kHz resolutions to achieve scanlines even on a 31khz monitor. Unfortunately there always seemed to be random issues with some resolutions or frequencies not displaying properly. They could often times be fixed by changing some settings but then cause other resolutions to exhibit the same problems. Like pincushioning, warped image, vertical rollover, etc.

Well to make a long story shorter: A few days ago I started noticing the pincushion effect getting worse but was able to correct it to some degree by adjusting pot's on the monitor. Then as I was testing different resolutions and switching between them, it appeared to get stuck trying to change it. Made an unsettling noise (probably component shorting out) and the image onscreen suddenly looked washed out and getting increasingly whiter while starting to fade away. I unplugged the monitor and let it discharge itself for a few minutes. When I turned the monitor back on there used to be a NO SIGNAL message bouncing around the screen but NOTHING shows up. No Onscreen Display at all either. Just a whitish blank screen warped at the sides of the screen that I left on stupidly for about 5 minutes while I documented what was happening and took some pictures.

Well, shortly after that the display turned itself off and I immediately unplugged the outlet. There was a burnt smell coming from the monitor. I took apart my arcade cabinet to get to the back of the monitor and noticed what looks APPEARS to be several capacitors leaking. I had read it was common for Electrolytic capacitors to fail on Makvisions. It could be yellowish glue used to bond the capacitors. Hard to tell exactly, since I don't know what to look for. Nothing Black or burnt looking. And this could of been happening for quite sometime and I didn't pay close attention until now.

Did a lot of reading and came across an interesting read  https://www.gammaelectronics.xyz/trcswos2e_7.html

It goes over many things I think I experienced. Listing the Horizontal Output Transistor and Flyback failures which can trigger shutdowns of the monitor for safety reasons. Their appear to be many variables.

There is literally one CRT repair place I know of about (possibly one of the last left in the USA) an hour from where I live that could possibly repair it. If it's as simple as replacing all the capacitors, that would obviously be the best case scenario. I would feel nervous doing this myself and honestly Don't even feel safe plugging the monitor back in at this point as it could do further damage.

Anyway if anyone else could chime in with their experience or even suggestions on the best route to go, that would be greatly appreciated. Sucks that CRTs are going extinct and repairing them will soon be impossible due to inexperience or even parts being available to fix it.

[mamenewb100]

Tried plugging in the monitor again. You can hear the degaussing sound, main board has power with a green LED. However the screen does not turn on at all with no static or anything. It appears the yellow around the capacitors is probably just adhesive glue. Can't really get a good look at the board without moving the whole machine. It's possible some capacitors lifted but I don't see any obvious bulges or burn marks.

I've heard solder joints could have come undone too. I did use a small 4" inch subwoofer in the cabinet below the monitor which may have shook something loose. Lots of variables. Probably just have to have someone look at it. 

[mamenewb100]

And now I learned the Flyback is whats responsible for supplying voltage to the screen. So clearly that must have gone bad at the very least. And yes I keep replying to my own posts. At least I'm making an effort to learn this stuff. 

[grantspain]

i have only worked on a few of these chassis, its unlikely your electrolytic caps are causing this but it is possibility and indeed that is glue you can see
I would be looking at either a hv cap failure or flyback as the extreme pincushion prior to failure would point towards these, its also possible the HOT has failed as a result
These chassis have safety resistors on all critical voltages, when i get chassis like these for repair the first I do after inspection for the obvious is to dummy load the collector of HOT and check all the chassis voltages, 24v vertical deflection, b+, 12v and 5v ( chassis dependant of course and using a schematic for reference)
I do not think this is a job you can do unless your soldering skills and equipment are of a good level but if you were to try then i would suggest reading the HOT with a meter on diode test collector to emitter first to check for dead short and take it from there

[mamenewb100]

i have only worked on a few of these chassis, its unlikely your electrolytic caps are causing this but it is possibility and indeed that is glue you can see
I would be looking at either a hv cap failure or flyback as the extreme pincushion prior to failure would point towards these, its also possible the HOT has failed as a result
These chassis have safety resistors on all critical voltages, when i get chassis like these for repair the first I do after inspection for the obvious is to dummy load the collector of HOT and check all the chassis voltages, 24v vertical deflection, b+, 12v and 5v ( chassis dependant of course and using a schematic for reference)
I do not think this is a job you can do unless your soldering skills and equipment are of a good level but if you were to try then i would suggest reading the HOT with a meter on diode test collector to emitter first to check for dead short and take it from there

Thank You. By HV Cap, you mean High Voltage right? Makes sense that a component getting to hot, would trigger a safety shutdown. Or just flat out failing due to the stress. So it is possible the Flyback didn't get harmed. Although maybe not a rare part or expensive to replace anyway. Any input will help narrow down the problem and help the repair guy narrow down what the problems are. I'm hoping to have him replace the critical components causing the issue. Then I'd happily spend extra money to replace all the capacitors since they were probably cheap in the first place and do a yoke adjustment.

[grantspain]

so your tech should read all the high voltage caps in the horizontal deflection circuit, the HOT and check any fet's if fitted on this chassis
pretty sure this is a rebranded weiya 2929 monitor

[mamenewb100]

Just wanted to update on this and ask a few questions. I finally got around to looking at the monitor again. After finding out someone local  will not work on my monitor, I decided to take it upon myself to learn and try to repair it myself. Even if I end up dumping money, not fixing the problem, or (hopefully not) damaging something. It will totally be worth it for the learning experience. I had a little experience practicing with soldering/desoldering on test PCBs and doing some basic mods on other electronic devices. I have a multimeter, soldering station with iron, desoldering pump, solder, flux, wick, and all sorts of other tools neccesary for most repairs. Also have a capacitor replacement kit for replacing the old caps if necessary.

I have the main PCB and Neckboard chassis removed for work. The board seems relatively clean with no obvious burn marks or bulging capacitors. I removed one of the larger capacitors that looked like it could be suspect but it has the same ESR readings as a new capacitor, so it was likely fine. I DID however notice that there was a good amount of corrosion around the main fuse after I pulled it (Check the Picture). The fuse also had poor continuity in comparison to a new set of fuses that I ordered. Which I would think could cause some bad problems. Am I wrong thinking this could cause voltage fluctuations with a bad connection to the fuse? I noticed the picture on the tube would also wobble noticeably from even the slightest vibrations or touch. Which many say could be a connection problem or cold soldering joints. Also curious if it's normal for the neckboard to remove from the tube very easily? Felt like it was barely connected with no click or snap.

I also did find a small crack in the Flyback Transformer after removing some dust from the body. This may not confirm the Flyback is bad but based on the problems I've had, I don't know what else could have caused the sudden loss of picture. Also removed and tested what I believe to be the HOT. A transistor near the FBT. I'd read that it should be around 40 to 60 Ohms reading from the Emitter and the Collector. But I'm only getting about .7 Ohms which I would assume to be shorted. I could measure B+ and other areas in the power supply but as of yet I'm not sure how to safely do that. As I'd assume you would need mains power for that?

Biggest problem I have right now is finding a Flyback. Found out that the HI-2929D-01 I need to replace is hard to find. Only one guy on Ebay was selling new old stock of them but they are currently out of stock and won't be available for another 6+ months. Interestingly there is another number listed on the Flyback that reads 'MTI-LTC-031'. If you do a search it comes up with a HI-3129C Flyback that shares the same number and IS in stock right now. I'm wondering if anyone would know how to check if it's compatible with a HI-2929D? It does have the same looking pin pattern like it would solder in to the CB. But of course the voltages could be different. I've tried searching for answers on compatibility but any info on Makvision Wei-Yas seems very scarce.

So to keep things as short and concise as possible.. My rookie analysis of the problem without any in-depth measurements of voltages so far is that the Flyback is likely bad, fuse needs to be replaced, the HOT needs to be replaced along with possibly other transistors near the FBT, replacing old capacitors, and reflowing the board with fresh new solder. I feel at the very least this would get me power back to the tube unless I end up finding out the tube is bad. Which I don't think it is. Does this seem like a good direction to go in? I'd liked to hear other experienced opinions on what may be the best route to go or what may be a waste of time and unnecessary/risky. Appreciate any help or input as I know trouble shooting electronics can be a pain in the --I'm attempting to get by the auto-censor and should be beaten after I re-read the rules--. Especially without physically being able to work on it. Provided some photos.

[lilshawn]

i would go ahead and replace that flyback. it is most assuredly toasted with it looking like that.

as for the 2929 VS 3125, they are BASICALLY a similar monitor with a few differences... might be a dual focus vs single focus leads. in which case you can cut off the second lead at the flyback and throw some shrink tube over the nub. they are both the same size monitor so they should be pretty close.

if it' where me, I'd swap it with a 3125 if that's all I could get. if you don't mind waiting, wait for the proper part. (I'm a jerry rigger at work and we do what it takes to get games working)

you are going to want to go ahead and change out the HOT too as well. it might work now, but who knows how long it will last if it's had to drive that flyback.

[Zebidee]

I notice there is no metal shield / heat sinks around the flyback/HOT and a couple of other big transistors, even though there are holes in the chassis to screw them in. Can't be good 

[mamenewb100]

I notice there is no metal shield / heat sinks around the flyback/HOT and a couple of other big transistors, even though there are holes in the chassis to screw them in. Can't be good 

I removed the heat shields because changing out transistors and the flyback would be difficult with them left on. Definitely were on when the monitor was in use. 

[mamenewb100]

Thanks Shawn. Figured I could swap out the transistors and diodes in the same circuit as the FBT like Q40, Q41 and D43 in case they were weakened by the overvoltages. But I suppose that could be unnecessary other than the replacing the HOT. Maybe just flowing new solder to improve the joints would be best? I can get the flybacks meant for the Trisync monitors but have to order them from dodgy Chinese sites like AliExpress. Which could be a real gamble with unknown quality. Almost desperate enough to try though haha.

Still not 100% on which component is actually the HOT. Is it the small transistor to the right of the large one in front of the FBT? Been getting schooled on things like Snubbers, Damper Diodes, and Transformers. I'll probably need to fully learn all components on the board to really get a good idea of what's going on.

[lilshawn]

the HOT is going to be the big one you linked in your photo above. (q40)

it basically takes the raw B+ (190vdc some odd volts) and switches it off and on to ground...through the flyback, producing the highvoltage for the tube. see super simplified pic.

it's a good idea to swap out the snubber diode, the flyback and the HOT. it appeared to kind of work in one of your pics, so i wouldn't worry about any pre-driver transistors upstream to the HOT, as they are behind a layer of protection.

[Zebidee]

That is a great explanation lilshawn

[Jomac]

the HOT is going to be the big one you linked in your photo above. (q40)

it basically takes the raw B+ (190vdc some odd volts) and switches it off and on to ground...through the flyback, producing the highvoltage for the tube. see super simplified pic.

it's a good idea to swap out the snubber diode, the flyback and the HOT. it appeared to kind of work in one of your pics, so i wouldn't worry about any pre-driver transistors upstream to the HOT, as they are behind a layer of protection.

Just for future reference:
Nice simple explanation pic but you might want to flip the diode around, you have B+ going into the flyback and directly to Gnd through the diode, the HOT isn't going to be seeing anything.