Hi,

Thank you for reaching out to us.

It is highly unlikely the 3 PSU's are faulty. Apart from swapping the power supply units, can you try these PSU's on any other machine just to confirm there is nothing shorting the PSU on this motherboard.

You may also try to reseat the components like RAM and Graphics card .

If none of these works, Please send the desktop's service tag via private message. 

To send a private message, click on my name and click start conversation.
Thank you

I have a xps 400 as well with a blinking amber light  but no other lights. My computer has been down for a few months now and i already have tried two 375 watt power supplies and now a 430w.  When it first went down i had left my office and when i came back something was sitting on the keyboard.  It hasn't worked since then . I don't think that three power supplies could all be bad. I was curious as to if there could be a fuse somewhere or a reset that nobody has mentioned. Everything I've read says to check the red thing on the back of power supply to make sure its at 110. I did. It is. Any suggestions ?

suesalke

There are no fuses, or resets.

Are there any 'Beeps' [see page 22]?

Which 1-2-3-4 diagnostic lights located on the front panel are lite [see page 20]?

The XPS 400/Dimension 9150 Owners Manual, is Here:

 ftp.dell.com/.../dimension-9150_Service%20Manual_en-us.pdf

Bev.