Neotec 38" NT-35E med res problem

[Paladin]

I've got a 38" medium res neotec monitor in my showcase cab. The picture quality is fine, but the pincusion was off to the point where the remote board pot would not fully eliminate it. I've been searching on the web for info, and found a couple posts about a 5.6uf @ 50VDC bi-polar High Frequency cap on the pincusion board of the 27 inch med res neotec at location C19. I verified with my manual that the same value and location exists on my monitor.

I had planned on eventually replacing it, but when playing the game last week (Gauntlet Legends) after about an hour the screen began to shake up and down like a small earthquake, then after a minute or two the picture collapsed  to about 1/3 of the normal height. At that point I shut the game off.

Does anyone (Ken, are you out there?) know if the collapse may be related to the pincushion problem, or if it sounds like something else? I see a cap kit on Bob Roberts site for neotec 3500, is that what I need or will I have to piece a kit together? According to the manual there are 76 capacitors on the main board alone, do they all need to be swapped?

Any help would be appreciated.

Small update:
I turned the game on tonight, and the picture was full size but still jumping around like an earthquake. I tried messing with the remote board, and thumping the side of the game but nothing seemed to influence it. Every once and a while it would stop jumping and look normal, but it only lasted a second or two before it started messing up again.

I don't mind doing a kap kit, but want to make sure I get the right kit.
 

[grantspain]

if its affected by physical force then it is surely a dry solder joint/trace or connection problem

[qrz]

try resoldering the vert output ic.
the "up and down" motion would be vertical deflection .
a horizontal defect would affect side to side (E/W).....

qrz

[Paladin]

Someone has suggested it may be a flakey pot on the remote adjustment board.  I'll take a look at it today and see what I can find.  I hope that's all it is, as the way I built the cabinet doesn't allow for easy removal of the chassis.  Lesson learned on that one!

[Paladin]

Still no luck.  It doesn't seem to be related to moving the cab or wires.  I ran it for a while and the shaking got worse the longer it was on.  It's not just horizontal, it's also vertical.  I guess you could say it's pulsing in and out.

My hole in the back of the cab isn't big enough to get the chassis out, but I do see some signs of overheating on R424.  Per the manual, R424 seems to have a relation to the B+ voltage.

[grantspain]

if it jumping size then it does sound like an unstable b+,maybe the resistor is breaking down or maybe the b+ filter cap is leaky

[Paladin]

I got the chassis out, and a visual inspection showed a bad cap.  Cap C312 had a slightly bulged top, and torn label.  I checked the manual, and it should be a 2200uf at 35v, but instead it was a 2200uf at 25v.  Hopefully that's the problem.

I just bought  a new cap, but after removing the bad one, it seems like it was installed backwards.  Now I'm not sure which way the replacement should go in.  The chassis uses a black circle with one side filled in black to denote the direction.  All of the caps are installed with the negative side in the black filled hole, but the cap I removed was in the other way around.

How did the monitor even work if the cap was in backwards?  It was OK for the first couple times I played the game.  Should I install the replacement the same way as the one I removed, or not???

[grantspain]

i would put the cap in like the others not like the one you removed,if blows crapless then you know i am wrong-just don't have your face anywhere near the chassis when you power it up

[Paladin]

I replaced the cap as per the chassis, and it didn't blow.  Unfortunately the monitor still has the shakes big time.  Back to the drawing board.