External monitor for an old iMac?

**Chris** · 06-12-2011, 17:36

The monitor of our elderly iMac core duo seems to have bitten the dust. It is no longer the primary computer in the house so expensive Apple-authorised repairs are not viable.

As I can interact with the computer perfectly well via screen sharing from my new iMac, I would like to consider attaching a cheap (*very* cheap) LCD monitor to it and shoving the computer itself out of the way.

First I need to make sure it's the actual monitor that's failed and not the graphics controller. Does the fact I can see output on my own machine mean the old iMac's graphics controller is at work, putting out the pictures?

Or can anyone who knows about Macs interpret this screencap for me - it's from the System Profiler of the ailing machine:

**Chris** · 06-12-2011, 20:48

Update ... after being off at the mains for half an hour and then re-starting, it was fine again. I powered up and down a few times without issue, but then when I tried to set the iMac to sleep it all went wrong again.

On waking from sleep it did the happy Mac chime and then started up without the display running. I managed to get it back by powering down from the apple menu (via screen sharing) and then off at the mains for a few more minutes.

Apple Hardware Test says there's nothing wrong with the display. It's all very odd. Anyone got any ideas?

**Kymmy** · 06-12-2011, 20:53

Could be a number of reasons..

I'm more likely though to suggest that the video good signal isn't getting through though that could be the gfx card, cable or monitor..

Try wriggling the cable when it happens to see if there's any effect.. Apart though from trying a new monitor it's very hard to diagnose

**Chris** · 06-12-2011, 20:57

Wiggling cables on an iMac is a bit tricky ...

danielf · 06-12-2011, 21:01

Shake the machine vigorously then

**Kymmy** · 06-12-2011, 21:01

Sorry I thought you meant an earlier model... Used to deal with the power macs and duobooks (with the docking stations)

DocDutch · 07-12-2011, 06:13

How handy are you with computers Chris as it might just be dirt in the unit itself so opening up the imac came cleaning it out could work

haydnwalker · 07-12-2011, 08:39

Looks like a LCD cable fault inside the machine. I haven't had my hands inside an imac so unsure how they deal with video to monitor exactly, but had this same issue on a Dell Laptop not long ago and it was a loose/faulty LCD to Gfx card cable (that particular instance was a ribbon-type cable).

Gfx card would be OK as remote screen sharing is working (as all the processing is still done on the host machines video card). Your System profiler shows theres nothing connected to the Gfx Card under the Display Connector area. Check the System Profiler once the monitor is working (that should confirm or blow out my theory).

Websites such as iFixIt should guide you through taking apart/checking the internals of an iMac (Linky > http://www.ifixit.com/Browse/iMac_Intel )