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A(other) possible fix for a Mac that won't power up
Authored by: aMacUzur on Apr 12, '05 07:29:38PM

This is a copy of an email I sent in response to a mailing-list posting about a system that sometimes spontaneously re-boots after being shut down and sometimes won't boot when the power button is pressed (it was a MDD PowerMac). My (edited) response to the poster was:
Your problems might be related to the following:

It turns out that some of the ATI Radeon graphics cards (e.g., the 9000 in our ol' DualGig MDD) can cause/exhibit these problems when using the DVI-to-VGA adapter with certain kinds of VGA cables. VGA cables have some pins that are either present/wired or not because they are used to indicate the "kind"/size of montior (VGA, XVGA, etc. ... i.e., the pixel dimensions).

I've found that using some VGA cables (i.e., wired to indicate some monitor sizes), but not others, will cause the following behavior (sorry, I've not figured which is which):

- when the VGA cable is connected and you attempt to shut the system down, the system will shutdown then immediately reboot (i.e., seemingly can't be shut down)

- when the system is powered down (e.g., by removing the A/C power cord) and then the power button is pressed (while the VGA cable is connected via the DVI-to-VGA adapter) the system will not not start up until the VGA cable is temporarily removed

One can imagine why this scenario occurs when you consider that the ATI card must (somehow) be connected to the power-on logic/signals because it also has an ADC connector (that supports powering on/off the system via an Apple monitor).

Anyway, I hope this helps someone ... sometime.

(Great resource, this Mac OS X Hints ... nice job!)

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A(other) possible fix for a Mac that won't power up
Authored by: Bobr on May 01, '05 04:17:47PM

I bought a used G4 Quicksilver at auction. It looks in great shape, no damage, cracks or signs of misuse. Anyway I have no luck in getting it to power up. The Front panel light will not stay lit, but the fan is running and the little red light on the mother board is lit. The DVD/CD drive clicks quietly twice on start up but other than that there is no activity. I replaced the battery and used the info you guys posted about the power button located on the board also, but still no luck. Any other suggestions? Thanks.

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