Problem With Defender Monitor

tb lilley

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I have a problem with the monitor in my Defender. The monitor gives a nice, sharp, bright, vibrant picture. But, after about 10 minutes of being on the picture starts to drift downwards. Leave it for long enough (about half an hour) and the 'scanner' will be in the middle of the screen, and the planet surface at the top.

There's a remote board for the monitor, and provided the screen hasn't drifted too far down then I can trim it back into place. I'm pretty sure it's a monitor issue, but I'm having trouble identifying the chasis. Pics below.

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So, a few questions. Can anyone ID the monitor chasis? Is this a common fault? Any idea on a fix? I'm guessing it's a dodgy cap somewhere, which I'd be happy to replace if I knew which one. I'd hate to have to shotgun every cap on the board, so even some advice on how to narrow it down (if people think that it is a cap ....) would be gratefully received, as would any other advice if I'm barking up completely the wrong tree.
 
It's a K7000 chassis, and there are only 17 caps, so "shotgunning every cap" isn't that big a deal, takes about 15-20 minutes if you have experience, and ensures no other 20-yr-old caps close to failure can cause other issues after you fix this one. Cap kit costs $5 at most places.

Those chassis are notorious for cold solder and burnt traces, too, so go over it good while you have it out...
 
Thanks for helping with the id. I've replaced caps on boards before, so that wouldn't be a problem. I'm slow at it though, so 17 caps to desolder then replace would probably take me at least a couple of hours .....

Anyway, problem now appears to be solved. Thought it might have been a problem on the remote board, so unplugged the vertical position part. Made no difference.

Couldn't find a description of a fault similar to mine anywhere on the net, which I thought was odd .....

Chassis looks like it's had a fairly recent cap kit too ......

So, had a fiddle about with the vertical hold. Picture now locks and doesn't drift.

So bloody obvious. Didn't cross my mind that it might be the vertical hold on account of the tiny amount of vertical drift going on. Didn't help me that I could trim that out using the 'vertical position' control .... Still, you live and learn. Eventually .....
 
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