macpro 6,1

The initial "chime" sound is generated in software when your Mac passes the Power-On Self Test. If the chime occurs and/or startup continues, your Mac is working. The screen should light up, and draw a blank gray screen.

Then on to the disk Drive.

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Based on those symptoms, your graphics card is flaky, or your display is unplugged or flaky.

There is no other failure I can think of that would fail to show a startup screen, then work after a reset.

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On this particular Mac Pro 6,1 dark cylinder, users have reported that the ribbon cable connectors that connect all the cards together may tend to accumulate corrosion late in life. The "fix" is the same as for a dead backup battery: Perform the 32-step teardown and rebuild to get access to the battery, and change that battery while the unit is open.

This can provide relief because removing and replacing the ribbon cable connectors clears corrosion and refreshes their electrical connections.

When you format a paragraph the way you have been, it uses a monospace font, but highlights action words in purple and anything beyond a screenful scrolls off the page. It is really hard to follow.

Is the power indicator on solid, or blinking a code?

what are the symptoms when it does not start?