Random green Flash on Screen.

Long Hair

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Friday I picked up a Mario Bros Cab, and the guy offered me a Bartop game as well. I believe the Chassis in the bartop is a k7000, this is the one giving me trouble. I'm thinking it's a cap issue, but not sure. I did a half-ass cap kit with caps I had laying around. I plan on ordering the rest of the caps needed to finish the job. ? Should I order a drive transistor for the green as well or wait and see if the cap kit works? The chassis had P447 on it. Caps not done are c10=33uf c11=22uf c13=22uf c23=47uf c56=22uf and 3 bipolar 10uf's. Here's two pics of chassis. before and after cleaned with alcohol. Thanks Long Hair
 

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finish the cap kit replace the fly and test again.

just measure the transistors and see if you need a new one.
check for loose or broke pads/traces on all of them along with the rest of the chassis.

Peace
Buffett
 
The green flash is probably an issue with the green gun inside the picture tube.....unless you have a bad connection, drive transistors don't flash the screen, it's either all green or no green at all.
 
Probley a cathode to heater short in green gun in tube. I have a tube in the garage that does that. Verify with a rejuvenator.

Andrew
 
The green flash is probably an issue with the green gun inside the picture tube.....unless you have a bad connection, drive transistors don't flash the screen, it's either all green or no green at all.

It's not the tube. I swap out the tube with a good one. When the screen flashes green, most of the time the green color goes out. That's why I thought it might be the drive transistor.
 
my bet it is a cold solder joint, or a loose/broke, pad/trace.

re-flow the header pins on the chassis and the transistors on the neck board.

Peace
Buffett
 
my bet it is a cold solder joint, or a loose/broke, pad/trace.

re-flow the header pins on the chassis and the transistors on the neck board.

Peace
Buffett

I will do this when I receive the rest of the caps, should be Monday.
 
Finished up the cap kit today and checked for bad solder joints and the neck board, but couldn't fine anything. Still had the green problem, so I decided to check the voltage on the rgb signals coming from the pit boss game board. The red and blue read about 1.5volts, but the green was jumping from 1.2 to 1.8volts. I hooked up a Sega Dreamcast to the monitor and it works fine,so the game board must by crap. I have a new problem I found, the V.position control does not work. Any idea on what it would be, resistor maybe? Thanks Long Hair.
 

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every time i have had that issue the pot was broken.

you may not be able to see the break so i would wiggle it fairly hard to see if it is.

if not replace it and see.

Peace
Buffett
 
every time i have had that issue the pot was broken.

you may not be able to see the break so i would wiggle it fairly hard to see if it is.

if not replace it and see.

Peace
Buffett

Tried a different pot,but with no luck. Looking at the diagram it shows that Q9(Transistor NPN 2N3904) goes to the V pos. I checked that with the volt meter and the C=13volts,B=0volts,and E=0volts. The Reference voltages should be C=12.3volts,B=3.3volts,and E=2.6volts. So maybe this is the problem?
 
Issues are now fixed

The green flash was caused by the game board and not the Monitor,neck board or chassis:eek:. The Vertical Position problem was caused by a bad transistor @ Q9(NPN 2N3904). Thanks to all for the info, maybe this will be useful to someone else in the future.
 
I've been following this thread because I have a game which flashes a green screen randomly as well. What specifically was the problem in your case? Thanks!
 
The green flash was caused by the game board and not the Monitor,neck board or chassis:eek:. The Vertical Position problem was caused by a bad transistor @ Q9(NPN 2N3904). Thanks to all for the info, maybe this will be useful to someone else in the future.


thanks for posting the resolution.

i will keep that in the old memory as a thing to check from noy on.

Peace
Buffett
 
I've been following this thread because I have a game which flashes a green screen randomly as well. What specifically was the problem in your case? Thanks!

The only thing I did was remove the pcb. Today I put a new power supply in and the green flash wasn't there. So it might be a power issue, but I think there are bad caps on the pitt boss pcb to. Sorry I don't have a specific problem.
 
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