WG 7xxx picture goes black

mecha

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I'm not entirely sure which model this is, all I know is that it's probably the original one that came with my machine when it was Pit Fighter.

it's a 25", and the adjustments are actually built in to the chassis itself. I don't have the link to that monitor ID page that Ken throws around, and I tried looking on arcadecup and couldn't find anything that resembles what I've got I don't think.

the problem I'm having with it though is the picture will randomly go dark (like to where it looks like it's off) but it will still have power.

if I tap on the frame a little bit, the picture will come back, but then it'll fade to black again real quick.

so what am I looking at here, dying flyback or something else? it's worth noting that the neckboard is bent on one side, meaning it was probably broken in half once. I haven't bothered taking it off because of this.

any ideas? :)


EDIT: found the model number. it's a 25K7171
 
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well it doesn't immediately fade in or out, it does it gradually. you don't suppose it could be the tube at all? maybe not the tube itself, because when it comes up it gets bright and it's got good focus. it's not like it's very fuzzy.

another thing it does is it'll go from the whites being white, to developing a reddish tint at random, and then it'll go back.

and I think the focus got a little jacked up on it too, but it wasn't doing that today, today in fact was the first time I've seen it fade to like pitch black.

it does all these things on its own. when the picture's black the monitor's still on, it's not as if it's shutting down at all.

I popped the anode off, we'll see how swiftly and elegantly I can remove this partially cracked neckboard.
 
nothing looked bad. there were broken traces on the neckboard (probably from when it got cracked) but continuity checked out across the points. (it was touched up already)

the only area I really touched up was the neck socket, cause that's where the line of the crack actually went across.

for all I know though, reseating all the connectors is probably what got it. so far so good.
 
If you touched up the neck socket, that's probably what the problem was. I had one that did that, if the heater is making a bad connection at one of it's two pins it'll fade like that. Also if it was getting a reddish tint it may have been because the green signal was dropping out, which also could have happened at the neck socket.

If it does it again, while it's dark, look and see if you're getting heater glow at the neck. BTW the heater circuit is like the easiest circuit in the chassis so that would be a great thing if the neck glow goes away, you could fix it easily.
 
nothing looked bad. there were broken traces on the neckboard (probably from when it got cracked) but continuity checked out across the points. (it was touched up already)

the only area I really touched up was the neck socket, cause that's where the line of the crack actually went across.

for all I know though, reseating all the connectors is probably what got it. so far so good.

keep in mind , as the unit heats up any gap caused by a crack will open further and cause all kinds of headaches. as I stated before, it seemed more of a trace or solder joint problem
 
previous owner had it for years (used it on his route), said he never had any problems with this monitor (he's a technician by profession). it may just very well be its time, it's been in use for almost 20 years in commercial settings after all.

unfortunately he's the only guy I know with a rejuvenator (to check the tube) and he just had his knee replaced last week. I might just drop my U5000 in for the meantime even though it has gremlins of its own.

this neckboard crack I speak of, it's been that way for a looooong time, even after reflowing the neck pin joints it's still doing the same thing. it was actually working fine since I put it back together until I noticed there was a thick strip of black at the top and I went to adjust the V-pos and V-size. then it started acting up again.

is this another clue? lol
 
caps couldnt hurt..

also desolder and resolder the flyback and also r101-???(all the large resistors in that area) also id check the wires going form the fly to the neckboard tgo make sure one doesent have a bad solder connection.

sometimes UNDER THE SOLDER the traces get so tarnished/black that youll get intermittent connections. I would also make sure the fuse holder is good.. sometimes the fingers get weak and youll actually get voltage drop across the terminals and the monitor will shut down.
i woiuld reflow the video header pins because theyre almost always an issue as well.

i would also at least replace the caps next to the shutdown pot to make sure thats not a issue. i have seen those cause shutdown more then once...


its also possible the tube just sucks. next time it does this black out thing tap the neck of the tube near the guns and see if the pic comes back.. if so most likely a tube or neckboard issue.
 
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mysteriously, after I pulled the neckboard to check that R213 (the heat circuit thing) I saw nothing wrong with it, and seated it back on and had the machine on all day. (I even beat the game once :)))))) ... whooped M. Bison's ass) and it didn't mess up once.

usually it'll be fine until I start tinkering with adjustments. I had the brightness very hot on it from yesterday, so thinking the coast was clear, I dialed it down and well... the monitor didn't give me any grief today. even the whites held up.

so which one was the fluke: the monitor fading out (maybe it got jealous that I got my Polo fixed?) or the monitor working?

you decide. ;)
 
whatever... as long as it works now, all is good.. could be it just had a krappy connection on the tube pins itself or it wasnt fully seated... in either case glad to hear its alive and working again...
 
well, I've been busy with finishing up fixing a lot of other stuff lately, and rearranged my fighting game "stable" a tad. I knew this problem was going to resurface as soon as I moved my SFA3 cab, and it did. so I took another look at the neckboard and the solder joints for the R213 resistor actually looked very shitty. I fired up the desoldering iron and discovered that the solder pads were partially lifted on both legs of the resistor. when I said a few days ago that I reseated the neckboard and the problem went away, I probably accidentally had the resistor bent the "right" way. also, when I was tapping the frame and it came back on, the same thing probably happened, and the heat must have made the resistor move enough to not make good contact again.

scraped the coating off the traces and fed the legs through to those, actually one of them the whole trace started lifting too (the small segment that goes to like a 6 pin header on the other side?) so I soldered the resistor direct to the neck point in the circuit.

incidentally, when I desoldered all the socket pins, the one that's in the same circuit as this "heat circuit" also had a lifted solder pad.

I made all the necessary corrections, played the game through with Ken, whooped M. Bison's ass, and the monitor didn't black on me once.


I checked for neck glow when it was black. neck glow would disappear and then the tube would fade to black. that's why I checked the heat circuit resistor. :)

so alas... problem solved.

thanks gents.

EDIT: problem not solved. it did it again. LOL

what exactly does the CRT ground do?
 
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