Macintosh Computers: Low Battery Can Cause No Video

I have a Macintosh 475 computer that recently stopped displaying any video. The computer appears to start up normally, but nothing appears on the monitor. What could be causing this?
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The loss of video signal on some Macintosh computers can be caused by the lithium battery, on the logic board, having a low voltage. If you are experiencing a loss of video, you should follow these troubleshooting steps to determine the cause.

Macintosh models which can be affected: Quadra 605, Performa 475, Performa 476, LC 475, Centris 660AV, Quadra 660AV, Power Macintosh 6100, and the Performa 61XX computers.

Step 1
If possible, swap the monitor with a known-good monitor and video cable to isolate the issue to the computer.

Step 2
Reset the Parameter RAM (PRAM) by restarting the computer while holding down the Command-Option-P-R keys. Continue holding down the keys until you hear three startup chimes, then release the keys to allow the computer to boot up normally.

Step 3
If the computer still does not display video, restart the computer off a known good startup disk or CD-ROM disc. If video returns, reinstall your system software.

If you still do not have video, your computer should be brought to an Apple authorized service provider to have the lithium battery voltage checked. If the voltage is below 3.0 volts DC, the battery should be replaced. If the battery voltage is above 3.0 volts DC, the logic board is likely the cause of the no video condition and should be replaced.

Published Date: Feb 18, 2012