25" WG K7000 Horizontal Pos/Width problem

[stratjakt]

Ok, as the topic says, I have a 25" WG K7000 (In a Data East Cobra Command cab) which only displays an image on roughly the left 3/4" of the screen.  I cant adjust it out, if I screw with the hpos and hhold controls, the best I can get is to make it wrap around the screen, or go all wiggy with the hhold out.

The core on the horiz width coil was cracked, so I've replaced it.  I also installed a cap kit, and reflowed all the connectors, all of which made the picture clearer and brighter, and slightly more stable, but did nothing to resolve my horizontal width/positioning problem.

It appears the board has been modded/repaired in the past, as theres a black wire and a couple of caps soldered to the bottom, and a remote adjustment board attached which looks like someone added it later (no header pins, just soldered to the board).  I don't know if this has anything to do with it.

Any ideas?  Should I replace the HOT?  Could the pots be out of whack?  Anything else?

If any of the resident experts could point me to a likely cause and solution, they'd be da man..  This is just such a nice cabinet and screen.  If it comes down to it, I'll just drop 100 bucks on a replacement chassis, but I'd rather fix it myself (and learn a thing or two in the process).

Please help folks, this is such a cool ass pedastal cab, and it'll make a kick ass fighter cab when I'm done with it.

Thanks in advance.   By the way, the frame on a happ vison pro universal mount monitor is about 3/4" too deep to fit in a 19" neo geo "gold" cabinet.  No reason to add that, other than that it's news you can use.  Get a shelf mount.  Switching frames sucks.

[Ken Layton]

Check out www.jstookey.com/arcade/WG_25k7191/

Remember that vertically mounted games are adjusted with the vertical controls for the 'left and 'right' sides of the picture in those cabinets.

Sometimes capacitor C51 (not included in capkits) goes bad causing problems with picture distortion. Sometimes you must also replace the vertical output IC and the hor/vert processing IC must be replaced.

[stratjakt]

Thanks for the link, although there was really no new info there.  I'd already found the manual and that schematic, and the only diagram he has on there that's not in the manual is pasted inside of my cabinet too.

Its a horizontally mounted monitor, so this isn't the vertical curling problem he had.  I can only get it to properly display along the left 75% or so of the long axis of the tube, its definately a horizontal problem.

I've been trying to read and understand the descripion of the "horizontal oscillator and output" section in the manual.  It talks about C36, which I remember reading about in article on Bob Roberts site, the "critical safety cap".  Re-reading that article, http://homearcade.org/BBBB/csc.html it seems that this is what the mess on the underside of the board is about, that cap was at one time replaced, but they did it on the bottom, not wanting to fight to get that metal shielding off.  There's two of them down there, I think the other is C38.

So maybe C36 and/or C38 (which the manual calls the "S" shaping capacitor, which in my understanding, makes the beam go to the right) are my problem.

Thanks for your help, I'll mess with it some more tomorrow.  I have another 7000 chassis from a 19" monitor that I let the vaccuum out of, I'll use it as a donor, and see if that gets me anywhere.  Ordering all this stuff at 5 bucks a component starts to make a 95$ replacement chassis look like a good idea, of course the DIY spirit is strong with this one.  I want to understand what makes all this junk go, but analog components really aren't my strong suit.

Another (maybe related?) question, the cap kit came with a replacement for C204, a 4.7uF@160V electrolytic, with a note that is only used on the neckboards of larger monitors.  My neckboard does have a C204 spot, but it was a ceramic disc cap, so I didn't replace it (polarity?)  Does this make any sense to you?

[Ken Layton]

That black wire and the other capacitors & resistors soldered to the foil side of the board were done at the Wells-Gardner factory. Don't touch those--leave them alone.

As to the harness for the remote board being soldered straight to the main board---again this was something the factory did. Some had the harness wires actually soldered straight to the board while some harnesses had small white connectors from that harness soldered there instead. This was all done at different times during the long production run of the k7000 series.

As to that extra cap for the neckboard, if you have the neckboard with the ceramic cap then don't worry about it. You now have an extra electrolytic capacitor. Since your neckboard doesn't use the electrolytic then don't bother with it. Some neck boards had it and some didn't.

[stratjakt]

Thanks for your help Ken.   I replaced C51 - a little .64uf tantalum cap, which I wouldnt suspect would fail, you sure that was the one you meant? and I pulled IC1 and IC2 off of a known good chassis from a 19" monitor that I let the vaccuum out of.  Now I have two broken chassis   I even replaced Q6 ( i think, manual isnt with me ) a NPN 3904 transistor that come blister packed at radio shack for 5 bucks a piece.

Anyhoo, no change.  I went ahead an bought this on eBay Link, since it sure appears to be the exact same chassis I have, minus the remote adjustment board.  I'll keep my fingers crossed, and hopefully it works.  Or maybe I'll wind up with three broken chassis.  Cheaper than a wei ya or 8liners, and more likely to give a good result, if functional.

I'll replace the ICs in my donor board, and treat it to some new caps, and swap it into my Bad Dudes cabinet.

If you think of anything else that might affect this 25" though, let me know.  It's definately some sort of sync issue, I don't have the equipment or background to sort it out, though.  Playing with hpos I can get the image on the left side of the screen, slightly folded over, or on the right side, with much of it cut off.  As soon as it looks like its almost going to be right, it goes all candy cane koo koo on me.

PS, all that hackwork on the back of the board sure doesn't look "factory", but I guess if a guy is hand-modding a hundred or more boards a day, that's what you'd expect.  It looks like something a 13 year old would do while trying to mod his PS2.  *those* i can usually fix.

Thanks again for your help.  I'm sure I'll be back with more monitor woes.

[Ken Layton]

I had a monitor once that wouldn't center all the way. Turns out the horiz position pot was bad. It had a hailine crack internally. I replaced it and everything was fine. I got the pot from Mouser for 60 cents.

[stratjakt]

I replaced the HPos pot, even though it seemed to test OK on my ohmmeter (smoothly went from 0-~500 ohms), also replaced the HHold... Still no joy..  I scavanged every part I could off of another 7000 chassis (HOT, the L2 coil thats next to the width coil, the "critical safety cap"..).

The monitor says to jumper J1 and J2, and J3 and J4, and then adjust HHold until the picture stops rolling.. When I install these jumpers, the hhold goes completely out (barber pole patterns), and cant be adjusted anywhere near normal.  Does this make any sense, or shed any light on the problem?

Still waiting for that replacement chassis to see if I can make something working  between the two, hasn't shown up, and seller seems to be ignoring my emails :/

In the meantime I'll move on to my other arcade projects... I really want my 25" badass working, though..

Thanks for all your advice.

[stratjakt]

OK

So, I recieved my "replacement" chassis from ebay, as always "untested, as is, but marked working" on eBay generally means the seller knows damn well it doesnt work but wants to pawn it off on some chump..

So I visually inspected it.. looked okee-fine..  So I put it in, and powered it up, and with a blue flash, I blew the main fuse in the cab instantly (not the one on the chassis, the 3A fastblow in the cabinet.).  So, I replaced the fuse, disconnected the degauss coil (why not), and tried again, once again, blew the fuse instantly..

UNDAUNTED, I removed the chassis and took it over to my bench, and the wise words of Ken Layton rang in my ears  "Check Q11", the voice said, and that I did, and the collector was shorted to ground..  Ok, it was Randy Fromms troubleshooting chart, but I'm giving Ken credit just because he's helpful.

So, I took Q11 off the original chassis, and switched them, and reinstalled it..  With my last 3A fuse (cannibalized from another cabinet)

Limited success.. The screen came on, all blue..   After a little fiddling with the drive/cutoff/brightness/screen controls (I dont know exactly what I'm doing, but had an idea), I got something which looked somewhat like an image.  The monitor is functional, but still a little too blue.  It's a wee bit distorted up top, but I think its due for a cap kit, in fact, I think I'm going to take all the caps I put in the original, and swap them to this working chassis.  Theres also a bit of a herringbone thing happening, but this cab's had its ground loop cut, so I'll chalk it up to that for now..

Now, the chart talks of Q1, Q2 and Q3 on the mainboard (npn 2n3904s easily sourced at rat shack), and Q201, 202 and 203 on the neckboard (easily cannibalized from my junked chassis) - does this sound like something worth doing, or do I just need some skill adjusting drive/cutoffs?

Anyways, pretty longwinded, but I'm somewhat jazzed that I fixed my first dead monitor.  Thanks for your help, Ken, even if it didnt "help".

[Ken Layton]

Capkit the replacement chassis. You'll still need to play with the color adjustment pots on the neckboard. Set all the "drive" pots to about 10 o'clock and the "cutoff" pots to 12 noon as a start.

It's always possible that even the screen, brightness, and contrast will need to be adjusted too.

[stratjakt]

RESOLVED
I played with it a bit, and realized that no matter what I did with the blue drive/cutoffs, blue was on "full blast".  So I checked the pots with my multimeter, looked OK, so it must have been the transistor Q201 (or whichever is the blue amp one).

Anyhow, I clued in and just swapped neckboards with the original chassis.  The drives/cutoffs were never fudged with on it.  After a bit of adjusting, the picture looks fantastic.  I'll still do a capkit, and since I bought them, I'll go ahead and replace Q1 thru 3, but i'm happy with the way it is.  There's a slight burn-in on the left 80% or so of the tube, since apparently they ran it all messed up like that for awhile, but I'll deal with it - it'll be hardly noticable behind some lightly tinted glass.

I'm still flying somewhat blind messing with screen/bright/contrast, I searched around but cant find a really good tutorial on how to adjust this, but what I did was put bright/contrast at their mid pos', brought up a crosshatch, adjustted screen until I could see it, then fudged with bright/contrast until I liked it, then fudged with focus until it looked good and sharp - then I brought up color bars (Contra has pretty good screen tests for a cheapo jamma board), and tweaked the red drive since they looked dark.  Is this close to right?

Thanks Ken for all your help, even if you didnt know the answer to my problem in this thread, it seems every time I google for monitor info, your name comes up.  You're a breath of fresh air in this modern internet of "STFU RTFM N00B".