Mac Pro 2009 Nahalem will not turn on

Hi everyone,
I am new to posting on this forum. Today, my Mac will not turn on. This same problem happened about 2 months ago. I performed the ram reset and it turn on and operated perfectly until this morning. The problem happened again where it will not respond to the press of the on/off button. I have performed all the same steps, and still nothing. About two years ago I had added additional ram to bring it up to 20GB. I removed the the additional ram as part of the testing process and still no responce from the on button. Other forums have suggested replacing the power supply or the graphics card.

Any advice is greatly appreciated.

Thank you,
Art

If you're not getting even the slightest response, I am inclined to think the power supply has gone.

There are lights on the backplane board and if they fail to light it indicates a power supply problem. The links below are to a downloadable Repair Manual and Technicians Guide on your 2009 mac pro. It will have pictures to show you where to look and how to interpret them.

http://tim.id.au/laptops/apple/macpro/macpro_early2009.pdf - Repar Guide

http://tim.id.au/laptops/apple/macpro/macpro_early2009.pdf - Technicians Guide

Lisa

Hi,, Thank you very much for the information... I really appreciate it. After much contemplation, I have purchased a used power supply off ebay. It should arrive in about 7 days.
After I paid for the used power supply I decided to try one more thing, as not one of the suggestions in the manual brought my mac back to life. I held down only the power button while pluging the power cord into the mac and two red lights lit on the backing board. Both lights read ovtemp cpu a and cpu b... I have my fingers crossed that this indicates I made the correct decision to purchase a used power supply
Thank you for your help ! I will let you know how it turns out after the power supply is installed

The power supply has a fuse that can trip. Also have a read of this and the necissity of having the original system install discs on your model mac Pro:-


http://www.mac-forums.com/apple-desktops/267864-psu-failure-mac-pro.html

Thank you #harryb2448 for the info. I read the link you supplied and I would like to avoid going thru the hassle of constantly replacing the psu. Unfortunately, I am not the original owner of this mac, it did not come with system install discs :-(
I went ahead and opened up the power supply, I tried to find info as to where the fuse you mentioned would be located, however, I came up empty. If you or anyone has any info, I would greatly appreciate it ! Here are some photos of the power supply open

Located the 16a 250v fuse next to the plug connector. Continuity is good. Tested it with and without power. With power 120v is read.

While powered on I took a reading in dc. CN2 had 5vdc and the other blue and brown read 166vdc. ???.... Could that be right ? View attachment 23517

I seriously need help. New/used power supply came in and I installed it. The exact same pattern as the original power supply happens. During the power cord plug in the 2 red led lights flash once. Press the power button and nothing happens.
New Power supply is an exact match to origina. 614-0454l
Please advise. Need help.

Thank you very much