20EZ vertical collapse

mc300baud

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20EZ that has had a full standard cap kit done it. it would run fine for quite a while then get the jitters, so i got a filter cap through Dokert recently.

decided tonight that if i'm taking the machine to Bumbershoot to live backstage for the weekend i'd better try to fix the jitters. get the filter cap replaced, put everything back in and get it hooked back up. fire up the cab up and no picture.

quickly shut everything back down and check the monitor over... find that i forgot to reconnect the r/g/b/y yoke wires. hook them back up, double check continuity on the fuses (the big one checked out fine, the small 300MA DC fuse seems to check out ok sometimes and not others.) put the monitor back in and still nothing. turn the brightness up on the flyback and suddenly i've got vertical collapse.

did i fry the yoke? or is it likely there's some other issue now?

i can probably replace the 300MA fuse in the morning, assuming my local shop has 'em (i'll have to buy five, probably at $1.75/each,) and i'll try that of course, but is there something else i should look for? i suppose i can pull the chassis again and check the yoke header pins for cold solder joints... beyond those two things i probably don't have time for any major repairs and i'll have to pick another game to go with me.
 
Did you check the service switch? This often gets flipped on accident when doing a cap kit.
I'ts in the middle of the chassis. it should be flipped to the "normal" position.
 
The yoke is fine, it wasn't hooked up. The 300ma fuses can be found at Radio Shack. You may have created another problem, by applying power without the yoke hooked up. Guessing, I would say you may have blown IC 601, or one of the vertical transistors.
 
well, hot damn setting the service switch to normal seemed to solve the issue. thank you very much!

what the heck is the service switch for if it all it does is cause vertical collapse? (and something else i suppose since there felt like another setting beyond the one it was on and "normal.") i just flipped through an electronic copy of the manual and couldn't find what the stated use is.
 
figures. i even kinda looked at it while i had the chassis out and thought 'huh, i wonder what this is for?'

my plan now is to leave it running overnight and see if the picture is shaking vertically in the morning. hopefully with the new filter cap it'll all be better.
 
cool.

That question has been asked many times, and never really answered.

The service switch is there to assist in initial convergence. It's probably a holdover from old TV sets - almost all of the vacuum tube type delta gun sets have a service switch that does the same thing. By collapsing the picture into a solid line, and turning down the drive controls for one color at a time, you can get the initial center convergence set up more easily - i.e. you need to get all three guns lined up, so you get a solid WHITE line, not a white line with red peeking out at the edge.

These days most people use a crosshatch generator.

-Ian
 
that vertical line i got was nice and white so my convergence must be good.

after putting in the new filter cap i seem to get no more shakes or sparkles, and it's steady even after being on for at least six hours straight.

now if only somehow i could stretch the cab into a widebody...
 
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