iMac G3 slot: flickers, after 10 minutes shuts down

If you have done the usual stuff like resetting the PRAM and restarting from another volume (such as the Mac OS X installation CD), and the problem does not go away, it sounds like the monitor is dying.

I was having this same issue with my Imac G3 DV 450. Its been at it intermittently for awhile, even after i upgraded to 10.4. But now finally the monitor has died today. And it wont even boot up. Im gonna keep an eye out on this thread to see if your luck is any better.

Looks pretty much that your iMac ist going to die. It's time for a HD backup or a external HD case. Frequent issues of old CRT iMac is a bad flyback transformer due to permanet overheating the transformer's immer cabel insulation becomes poor. For electritians there are repair instruction in the net, but you need to be an expert.

Sorry for the bad news!


Intel iMac Mac OS X (10.4.6) (iMac DV 400), Classic II, Wintel XP Notebook(s)

My iMac (tray-loader) did the same thing. The problem was the analog video board, not the CRT itself. There is a safety mechanism in the iMac that prevents booting (or shuts it off) if the analog video board (and probably the power supply) is failing. In my case, the problem got progressively worse until it would no longer start up.

I managed to fix it using instructions in an Apple tech manual PDF I downloaded and a part I bought off of eBay. Unfortunately, that replacement part also died. So I made a "headless" iMac out of the non-video components, and it's been running better than ever since then.

This is what want to try next to disconnect the internal video board and get it up again. With my new OSX Mac I have the trouble to read old iMovie (OS9) files from an FAT-formated external HD

The limited lifetime of the flyback transformer which feeds the screen is due its small size and the poor ventilation within the iMac G3 body and the high temperatures inside.

Intel iMac Mac OS X (10.4.6) (iMac DV 400 - dead), Classic II, Wintel XP Notebook(s)

Mr. Watanabe, Can you tell us how you fixed your crt imac to work without the CRT, with an external monitor only? I need detailed directions.

This is for a tray-loader CRT iMac, not the newer slot-loader CRT iMac.

You remove the bottom panel from the iMac. You will notice several connector cables that go from the "carrier" (the housing the holds the drives, motherboard, and CPU card) to the rest of the iMac. There will be two or three, depending on whether your iMac has an infrared port (IrDA). One of them is a video cable. If you want to see if your iMac will boot up with the video disconnected, disconnect this video cable and start up the iMac. If it sounds like it is starting up properly, then this procedure should work (you should be able to shut down by pushing the power bottom and the hitting Return).

You simply need to connect an external VGA display to the video connector on the carrier. The problem is that it is an old style Apple video connector, not a standard VGA connector. So you can get one of these adapters on eBay

http://cgi.ebay.com/New-Switchable-Apple-Mac-to-VGA-Video-Adapter-TVCS-183_W0QQi temZ250073333243QQihZ015QQcategoryZ3759QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

I don't know about this particular vendor, but these yellow ones with one switch work very well and they are cheap. Set the switch to the side that says VGA/G3.

Connect the adapter to the carrier and connect the VGA cable to the adapter. This should drive a standard VGA external monitor at up to 1600x1200 (if your display is big enough). The other standard resolutions down to 640x480 should be supported.

That should you get it going again. I went one extra step and removed the non-video components from the system, and set them up on a shelf above my 19-inch external CRT. That is a more complicated process that requires taking apart the iMac. But it works very well.