Studio XPS 435 MT, won't start?

For starters when you press the test button on the PSU do the fans start up? If nothing happens then the PSU needs to be replaced. Do you see any diagnostic lights or hear any beeps? Try pulling all the RAM and then boot the system. You should hear beeps or see a diagnostic light pattern indicating no RAM detected. If not then it could be a MB problem. Try disconnecting everything from the PSU except the MB. If the system tries to boot then connect items one at a time to the PSU until the systems fails to boot. The last item connected is the source of the problem.

Thank you I will try that, I don't get any beeps, I don't have a test button on my desktop... No fans are running... I will try what you suggest and let you know. Thank you so much for the help...

I removed all the ram, and all the fans started running, but nothing loaded on monitor? I put the ram back in and now the fans will start, but stop?  Now what can I do? At least I know the PSU is ok... I guess... Could it be my hdd or what else?

I wanted to tell you when it started with all the fans running, the on light switch came on for first time.. The fans were really running fast....Since the on switch came on for first time, could it be something in the switch?  This is driving me crazy...

Another thing I just discovered, when I hold the on switch in, the light comes on and the fans run, but there is a clicking sound, when I do that???

I have to apologize as I did not realize that we are dealing with an old (14 years) system with no PSU test button. At 14 years it is very possible that the PSU needs replacing. I would also first suggest replacing the CMOS battery (coin cell) as it probably has never been replaced and odds are very good it is defective. Make sure you use a brand new recently purchased CR2032 battery. And leave the old battery out of the system for 15 minutes before installing the new battery.

As for the clicking sound, assuming you have an HDD and not an SSD, it could indicate a defective HDD.

Thank you so much, I have already put a new battery in, but didn't know to wait  15 mins, should I take it out and put back in?  Yes this is old system, I will order a new PSU, and also test my hdd... I appreciate all your help....

The 15 minutes is to ensure that the BIOS will reset. I believe that Intel also suggests the 15 minute time frame.

Happy to help out!

One last question... Could you tell me what kind of Power Supply Unit, would I need to order?  For my old XPS 435mt......Thanks again...

Although you said you have 435MT, the picture of your listing is for 435T aka 9000 or 9100.  If the picture is what you actually have, let’s correctly name it 435T/9000.  Otoh the actual 435mt is a black silver mini tower.

435mt

435T/9000

for 435T you can get an original Dell oem 475w psu (Dell P/N: F217J).  for 435MT the Dell oem psu (0N248K) is 360w less powerful.

both 435T and 435mt motherboard can use standard non-Dell ATX 24/8 pin.

not convinced you necessarily have a bad psu although it could be a possibility. having fan on/off is a bad sign of motherboard.  if you have an old working desktop, try borrow its ATX 24/4 pin psu to test motherboard.  Good idea to replace cmos battery first w a brand new battery and clear cmos settings via motherboard RTCRST jumper.

Yes I have a old desktop I can try to see if it works, that way I will know if it's the mobo...Thanks...

My desktop looks like the top one, is that 435T?   I just took my PSU out of old computer, the pins aren't as wide to hook up to mobo, and this pc, it has 24 pins on my other PSU it only has 20? Will that make a difference as far as testing my mobo...  where this one has 8 the one Im trying to use only has 4 pins.. Will it not work to check my mobo?   Let me know as soon as you can, I am disgusted...lol

You can use a 20 pin ATX psu to test motherboard w 24 pin socket.  You can also use a 4 pin cpu connector to test motherboard w 8 pin cpu socket.  

do remember to replace cmos battery with a new cr2032 and clear cmos settings via motherboard CLR CMOS1 jumper.  It is located at bottom of MB bth red and blue multipin headers.

The computer must be disconnected from the electrical outlet to clear the CMOS setting.
Remove the 2-pin jumper plug from pins 2 and 3 and fix it on 1 and 2.
Wait for approximately five seconds to clear the CMOS setting.
Remove the 2-pin jumper plug from pins 1 and 2 and replace it on pins 2 and 3.

service manual 

You have 435MT if your pc looks like top one. MT is minitower.  otoh 435T is full tower.

I see the CLR cmos1  2 pin jumper, don't see the 1 and 3...

Remove the 2-pin jumper plug from pins 2 and 3 and fix it on 1 and 2.
Wait for approximately five seconds to clear the CMOS setting.
Remove the 2-pin jumper plug from pins 1 and 2 and replace it on pins 2 and 3.??? I don't understand about the above changes? Also the red and blue??    I have worked on computers before, but not mobo..

Again Thanks for all your help...