wells 25k7131 chassis help and rehooking to monitor

arcadegarage

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wells 25k7131 chassis help and rehooking to monitor

hey guys,

just picked up a nba jam with a "bad" monitor. the owner said it had a bad monitor, but i'd like to try and hook it up first to see what i get. the chassis was sitting in a box on the floor of the game when i got it...maybe it's just as simple as hooking it up...hopefully. just not exactly sure where some of these wires go or what to do with them...especially unsure of where the cut black wire goes. check out the attached pics below. thanks!
 

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the 2 pin connector in pic #2 is for the degaussing coil. there's only one 2 pin header on the chassis, there's no polarity for this it can go on either way, since it's AC.

the black 4 pin connector in pic #2 is the yoke plug. it's keyed so that you can't plug it in backwards. you'll see this right next to the big capacitor labeled C36.

do you have a black wire hanging from the neckboard for the CRT ground? typically people cut the CRT ground wire in half and reconnect it again when they reinstall the chassis with a wire nut. you MUST have this connected, it goes to the spring looking apparatus that goes around the perimeter of the tube. if you have no wire connected to the CRT ground on your neckboard, do not turn the monitor on, ask for further instruction.

the suction cup looking part, the anode, goes into the hole in the top back part of the tube. hook one pin under the hole, the squeeze the other end in. you want it to hook under the hole, if it's in securely, close the suction cup around it.

last you plug the neckboard in, which is also keyed with a wedge-like triangle piece.

I think that covers everything.

for future reference, whenever removing the anode in the future, you will need to discharge the tube first. considering the chassis wasn't even hooked up, I don't think you need to do this since the monitor's sat for a long time, but to be sure, I use a long flathead screwdriver with an alligator clip attached to it, then you attach the other end to the monitor frame. touch the hooked up screwdriver to the anode hole on the tube, if you just ran the monitor and went to remove the chassis, you'll see a spark. :)
 
hooked up...still nothing.

well, i hooked up the the monitor to the chassis sitting in the box...nothing. i crimped the degaussing coil, fit the two-prong and four-prong into the board, hooked up the neckboard to the neck, and put the suction cups in the back of the tube...nothing. i did notice there was a spot on that monitor for a 6-pin and a 3-pin connector, but there was nothing from the board to hook that up to nor was there anything else hanging that could be used...not sure what that is for so it was left alone.

after all said and done, i noticed a connector left unhooked from the jamma harness. see attached pic. this harness was coming from the V-ground, V-blue, V-red, etc on the parts side of the board. the solder side must be the rest of the colors for the V i'm assuming (without takign the board off). is this the problem? or is it time for a new chassis?

thanks as always,

joe
 

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Sorry, I had originally replied on how to hook up your monitor but deleted my reply since Mecha replied first. Anyway, you want to make sure that your signal wires are connected to your chassis like in the picture linked below. Before you hooked up the chassis did you check the voltage of the power supply? If the power supply is bad then your board won't turn on which will also cause nothing to be displayed on the monitor.

http://www.jstookey.com/arcade/WG_25k7191/WG_25K7191_output.JPG

If I buy a game that's not working first thing I do is unplug the PCB from the harness, check the voltage of the power supply to make sure it's at the correct voltage. If it is I'll then plug in the PCB and see if the game plays blind. Even though nothing is displayed on the monitor if the board is working you should be able to hear it.

If you power on the game and don't hear anything try pressing the buttons or coining it up. Some games have the sound turned off during attract mode and coining it up will help make sure the game is working. If you know the dipswitch settings for your board or have a manual for it even better as sometimes the game could be in "test" mode as well which will cause it to not be audible. Having a spare working Jamma cabinet or a cabinet wired for the same type of board/wiring is very helpful as it helps you determine if the board you're using even works. If you have a spare Jamma board to try in the cab that's a lot of help as well.

There's a lot of things that you'll find are crucial to helping you troubleshoot a game, a multimeter is one of them. So if you don't have one already I suggest that the first thing you do before proceeding is to go out and buy one.

Anyway, before you can troubleshoot the monitor you need to be sure that, the monitor is the only issue. In other words make sure everything else works first.
 
new fuse...no change

before i read these posts, i changed the fuse and tried to power it on. when behind the game, i saw a flash of green light briefly then nothing...monitor is still blank. i'll have to see what else is going on. ive been told it is a bad resistor, bad flyback, etc. seems like it could be a lot of things.

i do not see another connector to hook the game board to the monitor...all i saw was the end of that harness i showed in the pic. that's annoying. i'll have to recheck again. monitors can be hard to troubleshoot, huh?
 
before i read these posts, i changed the fuse and tried to power it on. when behind the game, i saw a flash of green light briefly then nothing...monitor is still blank. i'll have to see what else is going on. ive been told it is a bad resistor, bad flyback, etc. seems like it could be a lot of things.

i do not see another connector to hook the game board to the monitor...all i saw was the end of that harness i showed in the pic. that's annoying. i'll have to recheck again. monitors can be hard to troubleshoot, huh?
I assume the flash of green was the fuse blowing? If everything's hooked up correct and the fuse blew there are a few common things that can cause it that I would check first. The flyback and/or horizontal transistor might be bad. Another possibility is the 4 diodes that make up the bridge rectifier (D19, D20, D21, and D22 if I recall) could be shorted. That's usually caused by not hooking up the monitor to an isolation transformer and if you bought it from someone it's hard to say what they might have done so that's possible.

The harness from our above pic is for the the video wiring. You're missing the male half of the connector that goes up to the monitor and plugs in on those 6 and 3 pin connectors.
 
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Your chassis looks like a Zenith K7000. If it is then you aren't going to find a replacement flyback for it.
 
Yeah, it is a 7000A and there are no replacement flybacks for them but a standard 7000 chassis can be installed in it's place if your fly is bad. I usually scrap 7000A chassis' whenever I find them and install a regular 7000 chassis.
 
i do not see another connector to hook the game board to the monitor...all i saw was the end of that harness i showed in the pic. that's annoying. i'll have to recheck again. monitors can be hard to troubleshoot, huh?
Do you have any other games you can look at and compare to this one? Do you have a multimeter to test the HOT, resistors and diodes?
 
well this is annoying

shardian is selling me his k7000 chassis. think i may put that in and maybe work on this chassis later.

monitors are greek to me, but willing to learn. i do have a multimeter...just not too sure what im testing and when (game on or off).
 
new chassis...3-prong connection vs existing 2-prong connection

i just tried to hook it up and i noticed there are different connections on the chassis i just got compared to the pics i sent of mine (i believe on the flyback that's going toward the iso transformer?). looks like the new chassis had a three-prong connection and i have a two-prong. i guess i could cut the old one off and attach to the new...just not sure which wires wouldgo where. suggestions?
thanks,

joe
 

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you'll probably find that on the one with the 3 pin connector, the middle ground pin either goes nowhere or is supposed to be screwed to the monitor frame. look for like a green wire there, if you keep this connector.

there is no like actual ground pin on the K7000. the other connector from your old chassis is the type I've seen regularly on K7000s.

you can desolder the new AC plug and put the old kind in, or you can splice then with butt connectors or something. doesn't really make a difference, it's just AC. or you can adapt your cabinet AC wiring to the new connector, if you have a donor laying around. you could use wire nuts or electric tape to try it out even, it won't hurt anything if you're careful.

some may not approve of my "in-a-pinch" methods, and I don't really care. the ideal way is to solder the old chassis power connector onto the new chassis, or adapt your cabinet connector to the new chassis.

I've had to do some scalping in my time... particularly with Japanese cabs and WG monitors.
 
hooked up new chassis - still nothing

well, i hooked up the chassis tonight. looks like i made a little progress since the monitor powered on making the buzzing/hissing sound, but still no picture. i hooked up the new chassis and put the old connector (2-prong) on the new chassis chassis. i butt connected the black to black and white to white...took out the middle green ground and dd nothign with it but lay it on the floor of the cab. so the monitor comes on, but no picture. you can hear the game playing. i played with all the pots and the remote pots...nothing. when i let off the power switch on the back door, a black and white rectangle appears and then shrinks in the middle of the screen to nothing...narrow (in width about 2-3 inches) and maybe 4-5 inches tall. i assume the fuse was good on the new chassis. there are two fuses on the floor of the cab where the iso transformer is...they dont looks cloudy or blown...what do you think?
 
visual inspection of fuses is generally useless. had some that looked bad that were good... others that were good that tested bad.

just run a continuity check out them.

is your monitor even turning on? I find it hard to believe that 2 separate chassis have the same problem.
 
If you see that box when you power down, that means your tube is getting juice. There is an 'image' there, but it is just really dark with either the screen gain turned too far down, or the brightness too far down.

Verify all of your connections, then turn up the screen gain on the flyback next time you turn it on. If you don't get an image, then your tube has got to be the problem.
 
And just to eliminate some simple stuff.....

How is your video input cable wired, what order are they in ?

1. Red
2. Green
3. Blue
4. Ground
5. empty
6. empty

1. empty or Ground
2. empty
3. Sync
 
I suspect a bad PCB or the video input wires not connected properly.


And just to eliminate some simple stuff.....

How is your video input cable wired, what order are they in ?

1. Red
2. Green
3. Blue
4. Ground
5. empty
6. empty

1. empty or Ground
2. empty
3. Sync

WG_25K7191_output.JPG
 
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