dlbagna
New member
In hopes of getting help, I figured I'd share my most recent experience with a problematic 25" K7191... With a P538 main board...
Problem
Intermittently, the monitor will start to over drive green, worst from left to right... See image links below... Sometimes cycling the power makes it go away. Most off the time not... One thing to note that when it's working, there is a thin green vertical line on the left edge of the screen regardless of the position of the image.
History...
Bought in dead condition... See thread Flyback Errupts! Reasons? (25K7191)... http://forums.arcade-museum.com/showthread.php?t=124185
Changed flyback, did cap kit... All was well... About a year later I did a tube swap with a TV tube... Reused the WG yoke... Again all was fine for about a year... Till the green screen of death.
What I've tried so far...
-Smalltownguy2 Rejuvenated the tube successfully with no faults... Green screen persisted..
-subbed in a neck board from a donor chassis I borrowed from smalltownguy2, same green screen
-moved my chassis to another 25" tube... Problem followed...
-tried swapping q1 with q2 to see if problem changed color... Nothing changed.
-changed q1, q2, q3 and their associated non polar caps and IC1 from smalltownguy2's working donor chassis. No change...
After studying Randy Fromm's trouble shooting flow chart I decide to check the B+ voltage for the heck of it which at that time I think it needs to be 123V... It measures 134.5V... So I figure I figure a bad voltage regulator a STR30130. By fluke I found one on a an old tv chassis that i had kept from a tube swap....
Anyhow... Swapped that in and changed C57 in case...
Fired it up and the B+ was now 130V... Still puzzled I looked up the regulator and it turns out it is meant to regulate at 130V... Matching the last digits of the part number STR30130... The 19" chassis uses STR3123 @ 123V. Monitor worked good for about a half hour, and the problem came back... Sorry for the tangential side note...
Pulling my hair our at this point... There isn't much in the green circuit that I haven't touched at this point.
Can Anyone help?
I've attached pictures of varying states.
Game Running
http://i868.photobucket.com/albums/ab248/dlbagna/game_runningMedium.jpg
No signal
http://i868.photobucket.com/albums/ab248/dlbagna/no_signalMedium.jpg
Red only test pattern
http://i868.photobucket.com/albums/ab248/dlbagna/red_onlyMedium.jpg
Green only test pattern
http://i868.photobucket.com/albums/ab248/dlbagna/green_onlyMedium.jpg
Blue only test pattern
http://i868.photobucket.com/albums/ab248/dlbagna/blue_onlyMedium.jpg
All colors test pattern
http://i868.photobucket.com/albums/ab248/dlbagna/test_pattern_RGBMedium.jpg
Final Note… moved all original components to the donor chassis (minus the voltage regulator) and it works fine… also tried to use a different video source...
Thanks...
Problem
Intermittently, the monitor will start to over drive green, worst from left to right... See image links below... Sometimes cycling the power makes it go away. Most off the time not... One thing to note that when it's working, there is a thin green vertical line on the left edge of the screen regardless of the position of the image.
History...
Bought in dead condition... See thread Flyback Errupts! Reasons? (25K7191)... http://forums.arcade-museum.com/showthread.php?t=124185
Changed flyback, did cap kit... All was well... About a year later I did a tube swap with a TV tube... Reused the WG yoke... Again all was fine for about a year... Till the green screen of death.
What I've tried so far...
-Smalltownguy2 Rejuvenated the tube successfully with no faults... Green screen persisted..
-subbed in a neck board from a donor chassis I borrowed from smalltownguy2, same green screen
-moved my chassis to another 25" tube... Problem followed...
-tried swapping q1 with q2 to see if problem changed color... Nothing changed.
-changed q1, q2, q3 and their associated non polar caps and IC1 from smalltownguy2's working donor chassis. No change...
After studying Randy Fromm's trouble shooting flow chart I decide to check the B+ voltage for the heck of it which at that time I think it needs to be 123V... It measures 134.5V... So I figure I figure a bad voltage regulator a STR30130. By fluke I found one on a an old tv chassis that i had kept from a tube swap....
Anyhow... Swapped that in and changed C57 in case...
Fired it up and the B+ was now 130V... Still puzzled I looked up the regulator and it turns out it is meant to regulate at 130V... Matching the last digits of the part number STR30130... The 19" chassis uses STR3123 @ 123V. Monitor worked good for about a half hour, and the problem came back... Sorry for the tangential side note...
Pulling my hair our at this point... There isn't much in the green circuit that I haven't touched at this point.
Can Anyone help?
I've attached pictures of varying states.
Game Running
http://i868.photobucket.com/albums/ab248/dlbagna/game_runningMedium.jpg
No signal
http://i868.photobucket.com/albums/ab248/dlbagna/no_signalMedium.jpg
Red only test pattern
http://i868.photobucket.com/albums/ab248/dlbagna/red_onlyMedium.jpg
Green only test pattern
http://i868.photobucket.com/albums/ab248/dlbagna/green_onlyMedium.jpg
Blue only test pattern
http://i868.photobucket.com/albums/ab248/dlbagna/blue_onlyMedium.jpg
All colors test pattern
http://i868.photobucket.com/albums/ab248/dlbagna/test_pattern_RGBMedium.jpg
Final Note… moved all original components to the donor chassis (minus the voltage regulator) and it works fine… also tried to use a different video source...
Thanks...
Last edited:

