PTK195 based focus/screen block potting cracking.

[Jason D.]

While fixing on a lightbox with twitchy focus in green CRT, noticed
something unusual so wanted to say about that cracked potting in these
modules:

I had to check on two other lightboxes to find one that's not cracked
and swapped it in other set I was working on to test, this improved
somewhat but focus still is twitching.

Well, on the focus thing, it does like this, always on that green CRT,
slowly becomes unfocused then snaps back to in focus, over and over.
Also I noticed while adjusting that focus pot for green, it's not
smooth adjustment (focus goes in steps, not linear like other red or
blue does). Same problem with old or subbed from another set of f/s
blocks.

I know these has dynamic focus feature.

Interesting and any comments on both focus problem and potting
material cracking?

Cheers,

Wizard

 

[Bill Jr]

Jason,
We recently had a similar problem on a 195 chassis.
Turned out to be some contamination under the silicon that holds the plastic
piece on the end of the CRT.
Also had to change the CRT socket on that one.

Hope this helps.

Bill Jr




"Jason D." <jpero@sympatico.ca> wrote in message
news:4070ce19.96712904@news1.on.sympatico.ca...

While fixing on a lightbox with twitchy focus in green CRT, noticed
something unusual so wanted to say about that cracked potting in these
modules:

I had to check on two other lightboxes to find one that's not cracked
and swapped it in other set I was working on to test, this improved
somewhat but focus still is twitching.

Well, on the focus thing, it does like this, always on that green CRT,
slowly becomes unfocused then snaps back to in focus, over and over.
Also I noticed while adjusting that focus pot for green, it's not
smooth adjustment (focus goes in steps, not linear like other red or
blue does). Same problem with old or subbed from another set of f/s
blocks.

I know these has dynamic focus feature.

Interesting and any comments on both focus problem and potting
material cracking?

Cheers,

Wizard