Monitor has no red!!

jcterzin

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Ive been playing my paperboy that I just fixed, but the monitor is no spring chicken. It looks downright ugly so I decided to run it through test mode to check out the colors. When the screens that come up showing test color, the red channel is completely blank!! check the pics to see what I mean. Another thing is that on the top part of the monitor (check images) you can see on the blue and green that there is a color shift as well. WTF! Could the red wire connecting to the monitor chassis from the board be messed up?

Also, if I tap the side of the cab, the monitor flickers... bad ground?
 

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Check your game board connector & re-seat if necessary. I have a JAMMA cab that likes to lose green if the connector's not seated properly.

Do you have the ability to test the monitor on another game?

Also, flickering monitor on impact could mean lots of things. Cold solder joint, loose neckboard socket connection, lifted trace somewhere, etc etc...the possibilities are endless. Now, if you were to say that smacking the cab makes red go away and come back....THAT would be helpful. But don't go smacking it more just to see :)
 
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find the 3 pins on the monitor chassis that are RGB. With the power off, swap the R & G pins, and you'll likely have red but no green - then put the pins back where they belong. trace back to the board to see where the red voltage stops.
 
find the 3 pins on the monitor chassis that are RGB. With the power off, swap the R & G pins, and you'll likely have red but no green - then put the pins back where they belong. trace back to the board to see where the red voltage stops.

that is kind of what happens. When I swapped the pins, the red test screen that should show red now shows green. and the screen that is suppose to show green now shows nothing.
 
that is kind of what happens. When I swapped the pins, the red test screen that should show red now shows green. and the screen that is suppose to show green now shows nothing.

then it's not in the wiring. start looking toward the red drive transistor. your problem lies in the neckboard somewhere, yeah
 
then it's not in the wiring. start looking toward the red drive transistor. your problem lies in the neckboard somewhere, yeah

What does a red drive transistor look like on a 19" WG k7915 medium res? Im not familiar with monitors. Its on the neckboard though?
 
Here's a shot of one of my neckboards, with one of the transistors circled in red. There's 3 of these drive transistors on the neckboard, and you can usually tell which one goes to which color by reading the silk screen printing on the back of the neck board.

neckboard.jpg
 
Here's a shot of one of my neckboards, with one of the transistors circled in red. There's 3 of these drive transistors on the neckboard, and you can usually tell which one goes to which color by reading the silk screen printing on the back of the neck board.

neckboard.jpg

So i looked over those three transistors on the neckboard and nothing is noticeably wrong with them. The red pot on the neckboard is not working either. I resoldered some components that looked like cold solders but to no noticable change. Guess Ill discharge the anode and take a look at the board. For the record, and besides the anode, where should you NOT touch the monitor while its on or off?
 
checked the traces and solder joints on the bottom of the monitor board and resoldered some. It fixed the monitor flicker a little, but nothing with the red. Red shows up at the top of the screen though... any thoughts?
 
Is the red pot good? Have you put an ohm meter on it an dialed it up and down?
 
That red at the top of the screen doesn't look to me like red, but rather magnetic interference with the green. That does seem to indicate your tube is capable of showing red, but not that the chassis is producing it.

Check the voltages for the three colors at the connector to the monitor. They should be about 2vdc. Then check them where they go into the neckboard. They should be about 6vdc. Then check the red drive transistor voltages against the blue and green transistors (one voltage will be over 100vdc if working properly) and make sure you check them while that particular color is supposed to be on the screen (color bar screen is best)...
 
That red at the top of the screen doesn't look to me like red, but rather magnetic interference with the green. That does seem to indicate your tube is capable of showing red, but not that the chassis is producing it.

Check the voltages for the three colors at the connector to the monitor. They should be about 2vdc. Then check them where they go into the neckboard. They should be about 6vdc. Then check the red drive transistor voltages against the blue and green transistors (one voltage will be over 100vdc if working properly) and make sure you check them while that particular color is supposed to be on the screen (color bar screen is best)...

all three of the colors (RGB) were giving me a reading right around 5 volts where they connect to the monitor chassis and all three of the transistors were giving me the same reading. Two of the legs were reading 15 voltsDC and the middle one was reading 125 vdc
 
im sorry but i vote tube.

Heres how to prove it. Youve already checked red input, youve already checked red output at the transistor. logic follows that its either a neck socket issue or tube issue.


The fact you see a little red on top of the green test screen DOES NOT mean that the red gun is working.

If the tube is magnatized a little, the red phospor on the front of the tube will attract the beam from the blue and green guns..


degauss the hell out of this thing and recheck. does the tube now show perfect green and blue but no absoultely no red? Then you need a tube.
 
ok, so I dont have a degaussing coil but I did have some neodynium magnets I used to test the monitor. on the red test screen, waving the magnets over the screen clearly shows that all three colors are showing up in a rainbow like effect where the text is. If the red is showing up when I do that, then the tube is working correctly right? at that point Its gotta be somewhere on the board. I have used an ohm meter on the pots so that may be the place to check next...
 
On degaussing....you can also run a corded electric drill near the monitor too. That will create enough of an electric field to assist in some degaussing if you don't have a proper degaussing wand.

Or you can build a degaussing wand :)
 
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