k4900 brightness issue

cleverlyj

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So, i fixed my green issue. don't know exactly what i did, but i cleaned the dust off the neck board real well and touched up solder points that looked bad. have a new issue, though -

tonight, while playing, the brightness just cut out. i can still see the screen enough to play, but it's so dim you can't see the game grid, the white border is dim in the light cycle screen, and everything is generally real dark. it hasn't come back so far, which it did after a few seconds with the green issue.

anyways, i haven't pulled it back out to look at the monitor yet, but there was no noise, no smoke or anything, which would indicate to me a cap or flyback issue. any ideas?
 
and the damn monitor works again. after sitting for 20 or so minutes. ye gods! i'm getting tired of moving this cab around to get to the chassis. if anyone has a suggestion, let me know, but i'm gonna pull the chassis out and go over it and every piece of solder on it with a fine tooth comb.
 
Cap it and inspect the board closely for bad solder joints, particularly at the outer perimeter of the board. Sometimes bad solder joints develop at those jumper wires.
 
it has been capped already, ken. did that last week. i'll pull out the chassis though and check those joints. thanks for the tip.
 
There are several jumper wires around the outer perimeter that jump some of the foil traces. This is where bad solder joints are
 
I see this happen when it's internal. A short in the neck causes the heater voltage to drop. You can clear it out with a rejuvenator....
 
I see this happen when it's internal. A short in the neck causes the heater voltage to drop. You can clear it out with a rejuvenator....

hopefully that's not it. i didn't have the issue till i pulled the chassis to cap it so maybe i flexed it or something causing a cold solder joint. how much of a pain is it to rejuv a tube if needed?
 
allright. pulled the chassis and touched up all solder points, pretty much everything on the chassis. there were a couple that visually looked bad but everything looked ok for the most part.... took a look at the neckboard and all the solder joints on that looked good, so i didn't bother. so far it looks good as it did. i'll have to leave it on for a while and see if it dims again.
 
Did you check the tube socket solder points on the neck board? Bad solder point can also cause what Mod was saying about the heater.
 
i looked at them, but they looked fine so i didn't bother... i had it going for an hour or so with no issues after so i'm just gonna keep an eye on it.
 
just wanted to advise the fix on this.

for a while, the monitor stopped the brightness flickering, and then it would do it real intermittent. about 3 weeks or so ago, it permenantly went dim. you could still play, just a very dim screen.

anyways, i went over the neckboard and hit all the major solder joints (pins for the tube, and jumpers, and anything that looked crappy). no change

looking at the chassis, the pcb on the top right side was noticably black in color. went over every solder joint in that area, also the flyback for shits and grins, all the electrolytics, and i hit all the jumper wires on the board as well. that fixed it. unfortunately, as i didn't want to keep running from my work bench in my garage back into the game room and check progress, i can't say specifically what i hit with the soldering gun that did it, but it works great now.
 
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