I have an iMac DV preloaded with OS 9. Recently the screen goes flickery whenever I pull down menus.

A friend suggested turning off extensions by holding down SHIFT when booting up. That worked.

So I booted up again and turned off all extensions using the Extension Manager but the problem reoccurred.

What gives?

[Krusty]

Obviously, some extension is causing a conflict. Start by unchecking the most recentely installed extensions. If that doesn't work, try using 'Mac OS 9 All' and 'Mac OS 9 Base' extension profiles. That will at least help you to narrow down which extension(s) is/are the potential problem.

No, no. I can't even turn on a single extension without the screen flickering again.

Have you moved the computer recently or moved another electrical device closer to it ? Sometimes the electromagnetic radiation from other devices can cause screen problems. I also get monitor activity when I use my mobile (cellular) phone too close to the monitor.
Just a thought.

No. I set it up in a different room and the problem roccurred. There aren't any other electrical devices near by.

Strangely it's less apparent today.

I don't know if we're on the right track with this electromagnetic thing, but moving it has had an effect ?
Sometimes the cause is not immediately apparent. Remote control devices can cause problems as can more powerful devices. When you moved the computer, was it still near a common wall with the old location ? I realise it might be a hassle, but if the problem has become less noticeable, you could try another move.
Stab in the dark, Larry.

Depends on the lighting, too. Incandescent (sp?) bulbs are one thing, but fluorescent bulbs are another...sometimes the refresh rate of your monitor resolution setting does not react kindly to the cycles of the fluorescent bulbs overhead. In my old office, 60 Hz was unacceptable because of monitor flicker, but 72 or 75 Hz was wonderful.

There are electronic ballasts in some compact fluorescent lamps in homes these days too. The electronics in these can cause some interference with your monitor.

If it's really and truly not some outside interference, maybe it's the way your eyes see the refresh rate. You say it started happening one day. Had you changed the monitor resolution to run a game? Had someone else used the computer who might have changed something? There are sometimes more than one Hz setting per resolution on most monitors (I don't have an iMac so I don't know about yours). Look and see if changing to another resolution with a different Hz makes any difference to your eyes.

Good luck! It can be tricky to track these things down.

One other thing: You say it's flickery only when pulling down a menu? Is this while you're holding down the mouse button? Try this: Is your mouse hooked into the keyboard, or hooked into the side of the iMac? Whichever it is, try it the other way and see if that helps.



[This message has been edited by Linda (edited 03-07-2000).]

http://www.multimania.com/madrau/html/about.html

800 €600 is a great rez I have my mon. at that in 100Hz. This lil control panel will alow you to see in MUCH better detail how many diff things your display card is truly capable of.

Thanks for the tips. I tried switchres but it doesn't work. It seems my iMac only supports 3 resolutions with just 1 refresh rate each.
The problem does go away if I change to 640x480 from my usual 800x600.

I don't need to hold down the mouse button to get the flickers.

I think i've solved it. When I shutdown my iMac (usually I just put it to sleep) I get a screeching noise form the speakers. This according to miningco is a symptom of a bad power supply which can cause monitor problems. I'm taking it in for repair Monday.