WG 25K7501 - can't widen pic with width control

Bullwinkle

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I'm in the process of picking up caps for my Wells Gardner 25K7501. The monitor also has a remote board that has 7 pots, 1 for width. It is the only pot that has no effect on the picture. I've put an ohms meter to it, it's a 5ohm pot and I get 4.2 ohms to 0 ohms when I turn the pot... so the pot works, but where it's not showing a full 5 ohms, is this the problem? I have traced the cable all the way back to the monitor board and the cable is good. I could also reflow solder at the connector, but I'm wondering what else it might be and if there's any possibility that a cap kit will correct the problem.

Any suggestions?

Thanks,

-tom
 
Not sure what pot on the remote board you are adjusting, but neither of my WG 25K7's have a width adjustment on the remote board. You adjust the horizontal width with the width coil on the chassis. Or by changing the cap at C38 on the chassis as shown by Bob Roberts.... http://therealbobroberts.net/width.html
 
talking about this width pot (see pic). I have 2 california speeds, both have the same board. the pot works on one, but not on the other.

remote_monitor_board.jpg

I took the Ohms readings from the end of the cable, so I know it gets 4 Ohms to 0 Ohms back at the chassis board connector

Edit: I also just noticed there is no C38 on my chassis board. I've never messed with a width coil before, so I'll adjust that after I cap the monitor and see where that gets me.
 
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If yours has the separate transistor mounted on the back right part of the frame, you either forgot to plug it in or have it plugged in backwards.

If yours has that transistor mounted on the board:

http://forums.arcade-museum.com/showthread.php?t=127538

:D

entirely what I was thinking mod, lol.

if you have all 3 transistors mounted to the heatsink, going left to right, the 3rd one, make sure there's no solder bridges going to the cap that's immediately next to it, I made that mistake when I capped my 7500 (with great haste once the woman started bitching she wanted to go home).

otherwise, these will have 3 jumper wires going to another transistor mounted on the back edge of the frame as mod said, the connector itself is normally red (unless it's been replaced) and I don't know the wiring color order off-hand. in fact, all the K7500s in the games that I've fixed do not have this, I've only seen it on my junk chassis lot, and naturally they're missing that back transistor.
 
Not sure what pot on the remote board you are adjusting, but neither of my WG 25K7's have a width adjustment on the remote board. You adjust the horizontal width with the width coil on the chassis. Or by changing the cap at C38 on the chassis as shown by Bob Roberts.... http://therealbobroberts.net/width.html

That's for the K7000 series. The 7500 series (despite having a number in the 7000s) is a totally different animal.
 
If yours has the separate transistor mounted on the back right part of the frame, you either forgot to plug it in or have it plugged in backwards.

If yours has that transistor mounted on the board:

http://forums.arcade-museum.com/showthread.php?t=127538

I do have the transistor mounted to the back right part of the frame and it was plugged in. I tried plugging it in backwards and there was no difference. I ended up turning the width coil until it was wide, but I suspect that transistor (if working) would make it so I don't have to turn the width coil quite as much as I have. I held off on capping it as I wanted to try your suggestion, but I think that transistor is dead as I can plug it in either way or not at all and the screen does not change.
 
I'm now capping the monitor, and there is a 10uf 50v BP cap. One of the threads I saw regarding this said you could replace it with a BP or NP cap. I have a 10uf 100v NP cap which is 1/8 the size of the original BP cap. Is this an acceptable replacement?
 
Check the neckboard closely for bad solder joints. Those are notoriuous for failing around the color drive transistors. Jostling it around is sometimes just enough to cause them to come loose.
 
Check the neckboard closely for bad solder joints. Those are notoriuous for failing around the color drive transistors. Jostling it around is sometimes just enough to cause them to come loose.

Will do. I did replace some caps there too. Is the issue more likely on the neck board than the main board? damn I hope so..lotta caps put onto the main board
 
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Kevin & Peale,

Thank you!.. Yes indeed. someone had done some serious "retracing" on the neckboard for both green and blue..but not for red..and wouldn't you know it, one of the traces from the red transistor was dead. Now I have red again (and I'm a happy camper)

twins_after_capkit.jpg

The one on the right is the new one I just capped. It's like night & day from before. I just have to mess with the color a bit (little too much green I think)

Thanks again!

-tom
 
very frequently those color drive transistors heat the traces on like, every Wells monitor beyond the K7000. I've had nothing but problems on my U5000s, K7500s, and a D9200 with those traces lifting or the solder pads coming completely off.

I haven't come up with a solution for it either, I just wound up replacing the neckboards from dead chassis. lol except the D9200 I actually ran a jumper wire on the middle leg for the green transistor... it's held up over a year now, so I must have done something right.

inferior heatsinks, I guess.

glad you sorted things out though. :)
 
thanks, and yes...lots of repair tracewires already on the board around the transistors before I got to it. I got to add one more. they seem to hold even with the traces lifting. Seems like maybe something better than a cardboard heatsink is in order?? ;)

On another note, the transistor that was in the front of the monitor (attached to the frame in the front right) is broken, but... when it was in there..it didnt seem to do anything (no difference plugged in or unplugged). I suspected it was dead to start with but all the moving around broke a leg so it's toast now! :) I suspect I'll get a replacement on Monday, but the monitor itself is actually running fine without it. anyone know what it's purpose is?
 
If yours has the separate transistor mounted on the back right part of the frame, you either forgot to plug it in or have it plugged in backwards.

If yours has that transistor mounted on the board:

http://forums.arcade-museum.com/showthread.php?t=127538

Anyone know the part # to the transister modessitt speaks of? I'm not at home with my manual or machine and a lack of planning today..well..it's a typical Monday..., but I am 5 mins away from place where I can most likely pick one up. As mentioned, mine is toast, but the monitor is working. I'd like to replace it so I can hopefully get my width adjustment back.

No biggie if not, I'll check the manual or simply grab the part tonight.

thanks,

-tom
 
Damn...its not in the cali speed manual and i have the part in hand, but there are no distinguishing marks on the transistor. Anyone have the transistor part # or a manual to this monitor?
 
Monitor manual and schematics don't really show which one it is. I'll do some more looking, but I may need to just look at a chassis tomorrow at work...
 
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