Arcade game monitor problem

[Ken G.]

I have an old asteroids full size vintage video game .
I has a black & white monitor .

When it first comes on its fine . Within 10 minutes the whole image gets
bigger , things disappear off the edges . The center of the screen gets
a bit darker .
I suspected the hi voltage diode off the flyback and adjusting the hi
voltage pot but replacing that did not help .

I dont have any model #s the monitor has one medum circuit board and
one small board with the flyback in a metal box .

Thanks

 

[Franc Zabkar]

On Wed, 22 Oct 2008 08:22:07 -0600, goodguyy@webtv.net (Ken G.) put
finger to keyboard and composed:

I have an old asteroids full size vintage video game .
I has a black & white monitor .

When it first comes on its fine . Within 10 minutes the whole image gets
bigger , things disappear off the edges . The center of the screen gets
a bit darker .
I suspected the hi voltage diode off the flyback and adjusting the hi
voltage pot but replacing that did not help .

I dont have any model #s the monitor has one medum circuit board and
one small board with the flyback in a metal box .

Thanks

The "blooming" does sound to me like a low EHT problem. I'd check the
B+ going to the FBT, and the base drive to the LOP transistor. Make
sure the duty cycle doesn't change. I've seen this happen in an old
IBM monitor as a ceramic capacitor in the horizontal oscillator warmed
up. However, in my case the EHT gradually increased until the HV
protection shut down the monitor.

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.

 

[Ken Layton]

rec.games.video.arcade.collecting is the correct newsgroup.