Strange focus problem 21" monitor P810

[j. whang]

I acquired a viewsonic P810 monitor which almost works properly,
except for focus. It starts out from being extremely blurry and
then gradually (over few minutes interval) comes into fairly good
focus. However, the good focus dosen't last, and it abruptly
shifts back into extremely blurry focus, and then slowly works it's
way back to good focus again. This cycle repeats endlessly, and
leaving the monitor on for long periods has no effect on the
periodicity. It seems like there is gradual cycle of charging up
and breakdown of focus voltage somewhere, but I am at loss to
guess the first place to start looking. I've checked archive of
this newsgroup, but I don't believe anyone else has run into this
type of problem before. Any hints would be appreciated. Thanks

 

[Andy Cuffe]

I acquired a viewsonic P810 monitor which almost works properly,
except for focus. It starts out from being extremely blurry and
then gradually (over few minutes interval) comes into fairly good
focus. However, the good focus dosen't last, and it abruptly
shifts back into extremely blurry focus, and then slowly works it's
way back to good focus again. This cycle repeats endlessly, and
leaving the monitor on for long periods has no effect on the
periodicity. It seems like there is gradual cycle of charging up
and breakdown of focus voltage somewhere, but I am at loss to
guess the first place to start looking. I've checked archive of
this newsgroup, but I don't believe anyone else has run into this
type of problem before. Any hints would be appreciated. Thanks

It's almost certainly either the flyback, or the picture tube. I've
seen both types of failure in TVs and monitors. Either way, it's
going to cost more than a used P810 would cost.
Andy Cuffe
[email protected]

 

[j. whang]

Thank you for the advice. Actually, I've stumbled on the source of
problem. I was thinking it was very complicated and expensive problem
such as the ones you pointed out, but it turned out to be something
very simple. It was just that the crt board was loose from the
socket (perhaps due to bouncing around during shipping), and reseating
the crt board to the crt solved the problem.

 

[Art]

Seen sockets actually develop a high resistance short at the focus tab on
some sets. Replacing the socket, if available, tends to recrify the problem.
Also have seen focus packs, LOPT assemblies, and CRTs cause very similar
problems. Congrats on locating the "simple fix".