Atari APB Monitor issue WG K7915

pinballdirec

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I have been working on a Atari All Points bulletin with a monitor issue. Monitor is a Wells Gardner 7915. I'm only getting a white screen with lines thru it. (Pictures are attached) I installed a cap kit and it stayed the same.

I went thru a flowchart and it suggested checking the +123 VDC, the voltage was actually +123. It prompted me to turn up the "Screen" control on the flyback and I had the white screen (Raster) with diag. line thru it. It then prompted me to check the sync connected to pin 3 on P2 (It ohmed out ok) Next step was to check Q4 & Q7, I just replaced them. The flow chart stops at this point and I ran out of things to try. Hopefully someone can tell by my pictures what is going on...

http://www.klassicarcade.com/k7915a.JPG
http://www.klassicarcade.com/k7915b.JPG

Thanks Kevin
 
does the game play at all??

what you have looks almost normal to me without a game running on the monitor.

unhook the game signal and see what you get you should see raster and be able to make it go away when you turn down the screen knob on the fly.

if you get the same thing as what you posted in the pics then you are not getting any signal from the game.

Peace
Buffett
 
ok then does the game play at all??

as in even if you dont have a monitor in the cab. does it make sounds can you play it blind.

Peace
Buffett
 
ok

what happens if you max out one of the color drive pots on the neck board do you see that color filling the screen. try it with the rest of the colors to see if they are working.

do this with the video connector disconnected.

it will tell you if your colors are working or not.

after that we need to see hi res pics of the under and top of the chassis.

as you may have a solder bridge some where.
go over your work and see.

did you replace the fly on it. if you did do you have the wires connected up correctly.

Peace
Buffett
 
I would check the bottom connector going to the video board. One of the wires should be feeding 15vdc into it. make sure its there. have to pull a pinout to see which wire. That would cause your symtom.
 
After adjusted the neck board blue, red and green and wiggling the video cable from the board I was able to get enough of a screen to play the game. The video cable is a little flaky and will need to be replaced or repaired, but I do have something on the screen now.
I have the game in test mode and the red, blue and green look good, but the letters have tears in them. Thanks for everyone help so far. Besides a new cable any ideas to get a better picture? thanks Kevin
 

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After a little more adjustments the Graphics are pretty good now, but the text is very blurry and torn.
 

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if you cant get those colors to stop bleeding then maybe its time for a capkit, what happens when you turn , lets say the blue all the way down, will it still be bleeding or just gone?
 
his contrast is way to high to start.

i bet if ye gets the two brightness adjustments rite and then tweak the contrast it would look fine.

he should set all the control's to their center positions. neck board and chassis.

adjust the fly to get rid of the raster lines and get a good black then adjust the color pots on the neck to a good black level.
then adjust the contrast to a decent level.
and then fine tune his colors.

it would look even better.

then if needed adjust the brightness if needed.

that's what i would do.

Peace
Buffett
 
See below:

his contrast is way to high to start. (Is this on the Flyback?)

i bet if ye gets the two brightness adjustments rite and then tweak the contrast it would look fine. (One is on the flyback where is the second?)

he should set all the control's to their center positions. neck board and chassis. (ok)

adjust the fly to get rid of the raster lines and get a good black then adjust the color pots on the neck to a good black level. (Can you explain how to do this?)


then adjust the contrast to a decent level.
and then fine tune his colors.

it would look even better.

then if needed adjust the brightness if needed.

that's what i would do.

Thanks KEvin

Peace
Buffett
 
Thanks Buffet & Paul400 for all your help, I made the last adjustments that Buffet suggestions and I have a nice picture now. Kevin
 

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