Need assistance, never worked on a monitor before, screen is mostly blue. *Pics

infinkc

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Need assistance, never worked on a monitor before, screen is mostly blue. *Pics

From searching im pretty sure its a k4900 monitor, says RCA on a sticker, correct me if im wrong. Its in a Ms Pacman cocktail table.

The screen is mostly only blue color, not sure what color is missing to be honest.

Anyone have some suggestions on where to start off?

thanks!

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That is a 4900 and it appears that the blue and red are there but no green. This could be caused by a problem with the game board, but is more likely the monitor chassis. Take the chassis out, replace the old capacitors (install a cap kit) and then check over the entire chassis for cold solder joints. Pay extra attention to the blue circuitry connections.
 
That is a 4900 and it appears that the blue and red are there but no green. This could be caused by a problem with the game board, but is more likely the monitor chassis. Take the chassis out, replace the old capacitors (install a cap kit) and then check over the entire chassis for cold solder joints. Pay extra attention to the blue circuitry connections.

thanks for the sugguestion. Is there a way to test the game board easily? Also where to get a cap kit for this monitor? What do yo umean by blue circuitry?
 
I buy cap kits from Bob Roberts, but Zanen electronics sells them as well as a few others.

If you have another cab to put the board in then you can test it. Or you can put the monitor into another cab and see if the color issues clear up. Personally, I think you need to do the cap kit, be sure to check for cold solder joints while the chassis is removed.


When I said blue circuitry I was referring to the part of the chassis circuitry that directly converts the game board's color (I said blue but meant green) to the actual display. It is most easily traced from the green controls (pots) on the neck board. Everything connected from those pots to the green signal from the game board is a part of that circuit. Luckily, the color circuits are almost identical so you can compare all three and chase whichever one is different.


In my opinion you should cap the monitor first (checking for cold solder joints) and then retest to see if the problem clears up.
 
It does look like it needs a cap kit to me too, but...

The red looks over-driven too (horizontal smearing of red). Maybe try turning down the red gain on the neckboard. Perhaps someone monkey'd with these, and the green is turned way down, too...

Also, perhaps the brightness, contrast, black level and/or screen adjustments need to be turned down. Not going to make it look brand-new, but some knob-tweaking may be able to improve somewhat.

PS-RCA is likely the manufacturer of the CRT (the big glass tube) component. The whole monitor was made by Wells Gardner. You can get a manual for it here:
http://arcarc.xmission.com/PDF_Monitors/WG K4900_Manual_A.pdf
http://arcarc.xmission.com/PDF_Monitors/WG K4900_Manual_B.pdf

And Bob Roberts' cap kit page is here, scroll down near the bottom: http://www.therealbobroberts.net/caps.html
A cap kit involves de-soldering a dozen or so capacitors, and soldering in new ones.
 
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Darrenf thanks for the info.

Is there any other tests I can do to see if the signals are coming off the Main pcb ok? I have access to scopes, meters and just about any test equipment. Also rework is not a problem.
 
Is there any other tests I can do to see if the signals are coming off the Main pcb ok?

Just hooking it up to a known-good monitor. Can't say for certain, but your pic just looks to me like a tired and mal-adjusted monitor and an old tube with burn-in. Nothing screams out PCB problem to me. I'd do the cap kit, look for bad solder joints, re-adjust, and see what you've got then.
 
Still need some more assistance on this. I installed a cap kit and reflowed the entire monitor board and neckboard.

The transistors at the neckboard are not yielding the correct values, i swapped and installed new transistors for Q401, 402 403 and the image is still the same. These are the DC voltages im getting.

Not sure what to do next.

Transistor C B E
Typical V 139 9.7 9.3

Q401 92.7 9.8 9.4
Q402 104.2 9.9 9.3
Q403 45.9 11.5 10.9


Something is not right on Q403, the old and the new transistor yield the same values.

I dont have another monitor or board, this is my only system.
 
i need to know also, if im able to test the monitor circuit board without having it plugged into the tube? or are the expected readings that the manual has is when everything is connected?
 
I'm guessing it's one of two issues:


  1. Neckboard issue: one of the drive transistors or resistors has failed. Try swapping the blue drive transistor with one of the other two and see if the color issue follows the transistor.
  2. Tube issue. Your tube could have an internal issue. If you can find a 19" tube TV with a 10 pin neck (CR-23) then you might be able to do a tube swap. This is a much more adventurous route.

Honestly, the best thing you could do is load up your game and take it to someone else who has another arcade cabinet. Try plugging in their monitor to your game, and your game to their monitor. That will rule out the possibility of the problem being with the game board itself. (though I doubt the issue is there)

I do have the ability to bench test a 4900 monitor (like yours), so if you're willing and/or able to send me your chassis, I could work on it for you. But if you're going to go that route, I'd contact someone like Modessitt to get it semi-professionally repaired.
 

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I'm guessing it's one of two issues:


  1. Neckboard issue: one of the drive transistors or resistors has failed. Try swapping the blue drive transistor with one of the other two and see if the color issue follows the transistor.
  2. Tube issue. Your tube could have an internal issue. If you can find a 19" tube TV with a 10 pin neck (CR-23) then you might be able to do a tube swap. This is a much more adventurous route.

yea i already changed out the transistors to new ones and that didnt help. hopefully its not the tube.
 
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