Hi, @UndeadPianist16 ,

Does anything in this old Post help?? 

https://www.manualslib.com/download/553552/Dell-Xps-400.html 

XPS R Series is MUCH OLDER than the 2006 XPS 400 so no that does not help.   The R400 is from 1995 to 1998

R400 meaning PENTIUM 2 400Mhz machine.

You have to be someone who used MSDOS and then Windows 1.0 2.0 3.0 etc to remember the XPS R400

This specifc model uses VERY proprietary Power supply.  Dell part number is 9228C.  Its a NON PFC power supply.

NO other unit will work.  Using that psu in another machine OR a regular psu in that machine will literally blow up and catch fire.

DANGER WILL ROBINSON.

The good news is that several other models use it.

https://www.startech.com/media/products/ATXPW300DELL/PDFs/ATXPW300DELL_Datasheet.pdf

https://www.newegg.com/startech-com-atxpw300dell-300w/p/N82E16817707050#

Found a vendor that makes the CONVERSION Adapter.

HOWEVER the power supply used must be NON PFC

https://www.amazon.com/Connector-Dimension-PowerEdge-Precision-WorkStation/dp/B0042GMAY2/

The PROPRIETARY Dell 9228C PC Power Supply is compatible with

Dimension Series Models:
2100 / 4100 / B1000R / L Series / V350 / V400 / XPS B Series / XPS Dxxx /
XPS Mxxx / XPS P133c MT / XPS Pro 180n / XPS Rxxx / XPS Txxx

Optiplex Series Models:
GN / GN+ / G1 / GX1 / GX1p / GX100 / GX110 / GX115 / GX300 / Gxa / Gxi

Power Edge Series Models:
2100 / 2200

Precision Workstation Series Models:
210 / 400

Hi, @UndeadPianist16 ,

Ignore the Link, in my Post, to the Manual - it is the incorrect Manual!!

However, as far as I can tell, my reference to an earlier R400 Post (within this Forum) is valid!

Yes

Your post links 2006 XPS 400  This is Pentium 4 system.

Specifically a pentium 4 PCI-E system

https://www.manualslib.com/download/553552/Dell-Xps-400.html

He has 1998 XPS R400 this is 400Mhz Pentium 2 system.

This is an AGP and PCI system from 1998 and uses specific power supply  dell 9228C

They are both XPS and Both Dell but wayy different.

He uses ancient vaccuum tube machine to run really old games.

You were trying to be helpful.

https://www.cnet.com/products/64mb-for-dell-dimension-xps-r350-r400-r450/

Hi, @speedstep ,

You wrote:- "XPS R Series is MUCH OLDER than the 2006 XPS 400 so no that does not help."

Sorry, not certain which Post you were responding to, but I'm assuming that its my Post??

My post referred to a Post (dated 2004 - hence BEFORE the XPS 400 existed) & specifically mentioned the XPS R400!

The other post is valid but the endpcnoize adapter cable isnt available anymore.  Athena makes one however.

http://athenapower.com/node/177

The 9228C proprietary power supply references are the same and I found another vendor that makes the adapter.

But you have to use NON PFC power supply for these old models.

Using 9228C  on wrong model or standard power supply without an adapter will fry motherboard and cause a fire!

Thats why Startech made specific 300W replacement for these also NON PFC.

https://www.amazon.com/Supply-Designed-Replacement-Specific-Proprietary/dp/B000LRIWRK

https://www.startech.com/media/products/ATXPW300DELL/PDFs/ATXPW300DELL_Datasheet.pdf

For THESE MODELS ONLY

• Dimension 2100, 4100, B1000R, V350, and V400 replace
• Dimension XPS B Series replace
• Dimension XPS Dxxx, XPS Mxxx, XPS Rxxx, and XPS Txxx replace
• Dimension XPS P133c MT and XPS Pro 180n replace
• Dimension L-Series (LxxxR, LxxxCXE, LxxxCX, and LxxxC), replace
• OptiPlex G1 and GX1 tower systems replace
• OptiPlex GX110, GX115, GX300, GN, GN+, GXa, and GXi replace
• PowerEdge 2100 and 2200 replace.
• Precision WorkStation 210, 220, and 400 replace