Originally posted by Agent69:
1. What steps do you recommend to keep an iMac from loosing internal video due to that board that often dies in them?
There are two types of failures that the analog/video board can take, one is the horizontal flyback, and the other (I suspect) is due to a Philips chip that switches the monitor back on from sleep, and when returning from sleep doesn't give the monitor enough power.
I recommend that you avoid sleeping the internal monitor. Either use a screensaver, or shutdown, but don't let the monitor go to sleep.
2. Can you totally dim, or even turn off, the built-in screen of an iMac and still see the desktop on an attached VGA monitor?
If you can connect a VGA monitor at the same time as the built-in monitor, you must be talking about a slot-loading iMac. If this is the case, the answer is, not without difficulty. In a slot-loading iMac, it would mean complete disassembly of the covers, removing the video cable from it's port on the motherboard and reassembling the covers.
On a tray loading iMac, this is much easier, because the video cable is easily accessible, and has to be disconnected to connect an SVGA monitor in any case (exception, there is an adapter that allows both to be connected, but in my experience you get better use out of just using a larger SVGA monitor, because with the internal screen disconnected, you can display higher resolutions on the external display.)
3. If you set MacOS to make the monitor sleep after a certain amount of inactivity, will it make the external monitor sleep as well.
If you set Mac OS to make the monitor sleep, the external monitor should copy that behavior.
Really, the tray-loading iMacs were easier to deal with in many respects- when the analog/video boards of a tray-loading iMac fail, it's even-odds whether it will take out the power supply board at the same time.
On a slot-loading iMac, the video/analog board and power supply board are integrated, so if it's failed, there isn't much you can do with it. Avoiding letting the computer sleep is about the best way to prolong the machine's life, which I know seems backwards.
I've made an adapter to the ATX PC power supply for tray-loading iMacs, and am working on making a similar adapter for slot-loading iMacs, which would get around the problem of analog/video/power board failure, and be a relatively inexpensive way of avoiding an expensive repair. If you're handy with a voltmeter and want to help me with this project, email me.
-- thanks, Shmerek, you know more than you think you do on this subject!