What would cause my monitor to do this?

[mattpsu03]

Hello,

I have a Ducksan Type 20 13" CGA monitor which is displaying a strange screen. The strange thing is, I replaced the capacitors on the monitor board and it displayed perfectly for a couple days and I thought it was fixed. Well now it's back to doing this. Any ideas as to what might cause this screen? There is also a high-pitched noise when this is being displayed, and when I power down the monitor it fades to a white dot in the center. It's hard to tell in the pic, but the game does display very faintly inside the square. Could it be a flyback problem? Yoke issue? Bad tube? I've been troubleshooting this for a week now and I am out of ideas....

Thanks for any input...

Matt

[stj]

Re: What would cause my monitor to do this?

low B+ voltage will cause that.

what is it, a megatouch?

[mattpsu03]

Re: What would cause my monitor to do this?

Yes, originally a Megatouch 4. It's been upgraded to a Touchmaster 8000. Would a failing flyback cause a low B+ situation? Anything else it could be? I went over the board pretty thoroughly and couldn't find any cold solder joints and the resistors looked ok...

[mattpsu03]

Re: What would cause my monitor to do this?

Thank you for those schematics. Mine is the "O" version. I have been looking all over for that.

[stj]

Re: What would cause my monitor to do this?

lol - schems came from merit website.

the power section is top-left, 4 voltages.
you need to solder some wires so you can meter them and see if one drops when it goes bad.
probably the high voltage ones.
once you check that it will narrow it down a lot.