"ripple effect" on my monitor at higher resolutions

[rage12345]

When I first turn on my monitor (ADI Microscan 5v) it's able to display 1280x1024x32bit@75Hz. However, after running for about 20 minutes (i.e., enough time to get hot) it starts to produce a "rippling effect" (like when you throw a rock in water) that disappears when I turn the resolution down to 800x600x32@56Hz (even raising the refresh rate to 60Hz makes it come back).

It seems as though it's getting too hot to function at the higher resolutions so I've tried placing a fan from an old cpu on top of the monitor to suck the hot air out, but you can see the interfence from the fan even at 640x480.

I've tried the monitor on two different computers and in different rooms using different outlets.

Any comments/suggestion would be appreciated.

 

[crwpulsar]

The rippling effect could be cause by the transformer that steps up the voltage,at higher frequencies the dirrection of the current is changing to fast and the eddy currents in the transformer are getting to big,in a sence the transformer becomes an electro-magnet and drags electrons away from the screen.Best thing is to try running it at 60Hz/72Hz from the start and if it continues bring it to a shop to have the transformer checked.

Could be WAY off the mark but this is what I would do?
David

 

[rage12345]

I'm trying that right now and have a fan screwed to the top of the monitor.

What I had said earlier about the fan producing interference isn't totally true...it seems to produce interference only when the monitor is hot to start with (I had placed thefan on after the monitor was already hot it hopes of cooling it down.) so I'm trying it with a fan on in hopes that it won't get hot enough to produce the "rippling" in the first place.

What you said does make a lot of sense (espicially because then the monitor is producing the rippling effect, the small (normally insignificant) magnet in the fan produces more) but I don't want to put any money into it because it's already quite old.