Mac Pro 1.1 died. If no diagnostic LEDs illuminate, what does this indicate?

Ok, update. Forgot to mention I had already tried removing all components and also reseting SMC. Nothing. Not even a click sound of the relay when touching the power button. Found the service manual here: http://tesselator.gpmod.com/_Text/MacPro_Service_Manual.pdf

On page 120, it states:

Thank-you for confirming my suspicions. I'll look for a replacement power supply.

For those that would like to test this Apple DPS-980AB A power supply (for any power problem), this may help. Power supplies can be dangerous so you are at your own risk!

There are four connectors coming from the power supply: J1, J2, J3, and a fourth unlabeled one (i believed call "C"). You want to test the fourth unlabeled one, "C". On the "C" connector, connect the PSU ON pin (#8 in diagram) using a paper clip or small jumper wire to a nearby ground pin to ground (#2, #5, or #10). Please reference attached diagram below and the "J4" connector in the previously posted diagram in post above. Unplug all four connectors so the power supply is isolated, but plug in the 120v power cable. Using a multimeter, place one probe on a powered pin (see diagram) and the other on a nearby ground pin. If there is no voltage (+3.3V or 5V, depending on pin), then the power supply may need replacing or a new fuse.

You can check the power supply fuse also with a multimeter set to the Diode setting (look for symbol similar to below). Place a probe on each leg of the fuse. If you're multimeter reads "000" (and or beeps), the fuse is good (See: https://www.youtube.com/watch?v=HuWly36NyEE)

If the fuse is good and the power supply is working, you can move on to testing other things. FWIW, my power supply fuse tested OK, but the power supply PSU ON test failed.

Hope this helps.

Grant, thank-you for the info. Given there is no trickle power it is likely the power supply. However, it would be nice to know if a failed logic board can still illuminate the diagnostic LEDs. At this point it is difficult to tell if it is power supply, logic board, or both. Can a failed logic board still illuminate the diagnostic LEDs? If a failed logic board cannot illuminate diagnostic LEDs and no LEDs are lit, then it it may be more likely the logic board is the problem.

FWIW, the computer is used regularly and the power failed occurred yesterday while powered on. I did not notice any failure symptoms as I was using a different computer at the time.

I tried repowering many ways. With old battery removed. With new replacement battery. Unplugging power cord...waiting...etc, etc. following the Apple manual and other power related threads. In none of the attempts were any sounds heard (e.g., power switch relay) and pressing the diagnostic LED button each time resulted in no LEDs illuminating.

After about 6 hours of reading related threads and articles, I still haven't come across any info stating how to diagnose further when no diagnostic LEDs illuminate (including Apple's own manual). However, given Grant's comments, I'm inclined to think the power supply has failed.

For anyone replacing a Mac Pro 1.1 power supply, be advised: You have to match part of the serial number as well as the part number of the replacament power supply. Part number is usually: XXX-XXXX. The serial number is: XXXXXXXXEEEX. The last 3 of 4 letters or numbers (the EEE code) is the version number of the PSU. These letters/numbers must match or the power supply may not correctly manage the cooling fans.

Hi Grant, The replacement power supply arrived today and after installing, everything is back to normal. Thank-you for your assistance!