K7000 vertical linearity problem

Buffett

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Donor 2012-2013
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i have been working with this chassis and cannot figure out what is not working correctly.

back story on the chassis.

chassis was dead on arrival.
capped it re flowed it tested the H.O.T, VR, all the diodes in the hor/virt/power circuit installed a new fly. fired it up with out any problems.

B+ is good at 123v.

but cant figure out what is causing this vertical linearity problem.
i have measured countless resisters and diodes. and changed out all the IC's to eliminate them.

there is a factory mod on the chassis with a resister from the V-size pot to trace with C13 on it negative side. if i remove it it gets smaller but that is all it helps the but vertical linearity problem is still there its just squished more.
the resister is good when tested.

here is some pics and a video of the problem.
the video sucks as my camera is not that great.

video
http://www.youtube.com/watch?v=RKHp919GnJQ&feature=youtu.be

pic 1 is the best it will get with the pot at its minium.
pic 2 is with the pot centerd.
pic 3 is the pot maxed out.
so what would make this happen.

Peace
Buffett
 

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its a 19" p447 10 pin fat neck WG. not a K7000a.

what you see there is the best it will adjust even with the 50/60htz.

believe me this is the first time i have run across this problem.

i have done dozens in the past year 19-25" K7000's and never have seen this problem.

Peace
Buffett
 
got any donors? ive heard stories of all kinds of weied issues due to that little dipped tantalum cap changing value might be worth a shotgun swap..
 
witch one are you referring to there are a bunch on the chassis??

i do have doners i don't mind robbing.

Peace
Buffett
 
Those pics are showing as very little to me, so I can't see what the issue is...
 
OK imagine if you max out the V-Size pot on a working normal chassis how big the screen gets.

well on this chassis that is how big the screen is with the pot all the way down.
and if you max out the pot it doubles the image on the screen and rolls it half way back into the center of the screen over it's self.

so what main parts on the chassis control that part of the circuit.

Peace
Buffett
 
Which IC3 do you have? I know that when I tried replacing one with another of a different number, I had size display issues like this. If you put one from a 25" on there, that would cause something like this.

Normally, you'd check the 1000uf 25v cap at C50, as it handles thew up and down raster deflection through the yoke. There are some other resistors and ceramic/tantulum caps on that line that could also be an issue.

You could also check your +24 line to see if it is way off. R83 and Q9 handle the raster shift, but position doesn't seem to be the problem.

Feedback to IC2 control drive amplitude and linearity as size changes. You siad you changed the ICs, but perhaps some part on on of the input or output pins is off. Have you compared the voltages at the IC pins to what is listed in the manual?
 
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