Screen Flickers And Computer Shuts Down

GRMrGecko wrote:
I have a iMac G3 tray loading
every few minutes the screen flickers
sometimes it will shut down
sometimes i can't even start up it shuts down when the screen first turns on
i think it is the crt screen ding but i don't know
maybe if i can find a flat panel to replace the crt screen

can some one help me

Hi GRMrGecko,
Well that sounds like the PAV board is going bad. You could install the OS into a 400 iMac. They can be had for $25 around here. It would also have FireWire and be able to play DVDs.
Richard

Well the PAV generates all the voltages to drive the CRT. Then via the "Down Converter" (which in the slots sits right next to the logic board) converts the voltage from the PAV to logic board level voltage. When the PAV is going bad a current sensor will shut the board down when certain perameters are exceeded. Occasionally the PAV will fail but the voltage to the down converter will be OK and the logic board will still work and put out video. In the FireWire iMacs the VGA output will still work. In the Trays the out put is that gray multipin cable at the back of the mass store tray. It's "old Mac" and the adapters to VGA are still available.

Richard

so a imac g3 with firewire dose not go bad?
is that what your saying

No both can fail PAV wise but the slots fail less frequently than the trays. But then they're newer.
Richard

FYI - On an CRT iMac that is a tray-loader (not slot-loader), you can bypass the problem by disconnecting the internal video cable and connecting it to an external VGA monitor. It will even go all the way up to 1600x1200 resolution on a big enough VGA monitor if the iMac has the full 6mb of video RAM.

You will need an adapter. The internal video port is the old-style Apple video connector. You can see the type I used by searching on "apple adapter vga TVCS-183" on eBay. It's a little yellow adapter with one switch.

Connect that adapter to the iMac's internal video port. You can access the port by removing the bottom plastic panel. It's not labeled, but only one of the cables looks like a video cable. Undo that cable, connect the adapter (to the "body" side), and connect the cable to the external monitor to that adapter.

NOTE: You can't do this with a slot-loader.

It may not be too elegant, but it may work OK short-term until you get that new iMac.

You should be able to use an LCD, as long as it has VGA input and you use that adapter. However, I don't know of any "flat panel" LCD displays that have the old Apple video connector. They usually have VGA or DVI (or both). There are some really old Apple-branded fixed resolution CRT displays (not LCD) that use the Apple video connector. It's possible those will work without any adapter, but I've never tried it.

I used that adapter, connected through VGA cable to a 19-inch CRT display. I usually run at 1280x960 resolution, 75 Hz and "millions" of colors (Mac OS X 10.3.9). I can go up to 1600x1200 at 75 Hz and "thousands" of colors, but the text gets a bit too small.

If you already have a spare VGA display collecting dust, it may be worth getting that $7 adapter to try it.

Yes, I think it will fix the shut down problem. Apple designed those iMacs to shutdown if it detects a problem on the video board (probably for safety reasons). By bypassing the video board, the iMac does not detect a problem.

My old iMac started to shut down, and eventually it did not start up at all. It would power on, then almost immediately power off. Bypassing the video board allowed it to start and keep running. You can try it yourself, without the adapter. Just disconnect that internal video cable, then start up the iMac. You won't be able to see anything, but it should start up and keep running.