XPS 8700, power button does not work

I checked the Power ON switch and measured a resistance of 15 Ohm.  So I assume the switch is working on my XPS 8000.

An amber LED lights up on the motherboard when I connect the desktop to the mains.  But pressing the Power ON switch does not start the computer.

There was quite a bit of dust inside the desktop and also inside the power supply unit.
Also, for some time the desktop made often quite a bit of noise, noise I presume generated by the fan(s) (3 of them).  Maybe the power supply overheated and therefore is no longer functioning?

There is a small test button for the power supply on the back of the case. You can have PC off, plugged in, and pressing the test button should turn the power supply on while the button is depressed.

@GuillaumeCdB  - Do you mean it's a Studio XPS 8000, or is that a typo in your post?

If this is a Studio XPS 8000, it's hard to tell from the on-line docs if this model has the PSU test button on the back, but here are Dell's instructions to run the PSU "BIST" tests with or without that button. 

The amber light on motherboard only means it's getting "flea power" but that's not enough to boot the PC. And is it possible the switch has failed even though it has resistance?

Thanks, Ron for your comments.

It is an XPS 8000 (purchased in 2009).
Alas, no test button present, only the green LED that, I assume, lights up once the desktop is booting (which it does not of course).

Never heard of "flea power".

A resistance of 15 ohm is rather high for just a contact (measured between the pink and blue wire connections)...
I will try to temporary bypass/bridge the Power ON switch with a wire by connecting the 2 pins of the male plug at the bottom of the motherboard where the Power ON switch connector is plugged (I will have to remove the 2nd HDD to have easier access to the connector on the motherboard; I have a RAID1 configuration).

I can check the battery again but I replaced it not too long ago.

Willy

@GuillaumeCdB  Black is ground.  Yellow is +12V.  Red is +5V.  Orange is +3.3V.  (Assuming Dell followed normal conventions).

@GuillaumeCdB  The rear PSU LED should light up for 3 sec and then go out after disconnecting the cord from rear of PC, waiting 15 sec and then reconnecting the power cord to rear of PC with its other end already plugged into the wall, but without any surge protector or power strip in between.

So if you're not seeing the LED on for 3 sec, that suggests a failed PSU. Before buying a new PSU, you may want to strip PC down to bare essentials by disconnecting all drives, removing all PCI cards, except video card, removing all RAM, except the module in 2nd slot from CPU. Connect only mouse, monitor and keyboard and run the PSU test again. If you still don't see the PSU LED on for 3 sec, then it might be time to think about replacing the PSU...

EDITED

@GuillaumeCdB  You'll probably need to use the 'paperclip' test to turn the power supply on when not connected to the motherboard.  See here for the method.

And this solution, I might try first:

PSU test 

Willy

I removed the PSU, put a paperclip between the Green and a Black pin on the 20-pin connector, and also hooked up a case fan.

Result: the case fan did not run.
I tried the paperclip between Green and also other Black wires, with the same result.
I measured the voltage between B/Y, B/O and B/R and all were "0".

Conclusion: I must assume the PSU is defect and needs to be replaced.

The next problem: finding a replacement PSU (preferably in Europe).  I can try to contact Dell but I doubt if they have replacements PSU for an old(er) XPS.

Currently, I am using the XPS 8940 (purchased at the beginning of this year because of the Power ON problem with the XPS 8000).

Willy

It should be relatively easy to replace the power supply.  As I understand it, the original power supply was 350W and of standard ATX size, although you will need to confirm that.

There are people on the internet who will tell you categorically that you MUST buy a Gold+ rated power supply from their favourite supplier or you risk burning your house down / frying your computer / whatever.  Ignore them.  The computer probably isn't worth investing that much money in a new power supply.

Things you will need to look at:

1. Correct connectors for the Dell motherboard - as standard, an ATX power supply will give you an 8-pin and a 20+4 pin connector for powering the motherboard.
2. Sufficient watts on each of the power rails.  The current tends in computer power is to require less on the 5V rail as the newer motherboards split down the power from the 12V rail and so current power supplies don't supply as much.  An older computer like your XPS 8000 may require more 5V power than some power supplies now provide.

Also, I'd look for a semi-modular power supply.  Dell will have provided the power supply with the connections required for the computer.  Non-modular power supplies have a tendency to provide cables and connectors for anything they think you could possibly need, which leads to redundant cables having to be accommodated in the case.  A semi-modular power supply provides just two or three permanently wired cables to the power supply, usually those for the motherboard, and the rest plug in so that you only need to install the cables you require.

I recently purchased an Aerocool Integrator MX 600W modular, 80 Plus Silver, power supply from Amazon here in UK, which I feel is a good quality / price power supply and should also be available in EU.  You would need to confirm that it is suitable for the XPS 8000, though.

@GuillaumeCdB  I figured it was probably the PSU.

May not be so easy to replace the PSU in the Studio XPS 8000... Read this thread...

I do see some OEM Dell PSUs for this PC model on Amazon and elsewhere in USA, so look on the net to see if anyone is offering a Dell OEM PSU for this PC model in the EU...

Others have been successful replacing the Dell Power Supply in their XPS 8000 with a standard ATX power supply.  See here.  I know it's an old post, but does prove it can be possible.  The 4-pin power connector on the motherboard may be a problem, though.  The power supply I identified doesn't have a suitable connector, either on the permanently connected cables or the additional cables that can be plugged in.

I replaced the PSU with an ATX Corsair 350W and the desktop did start up.

Alas, de CMOS settings might been lost when I removed the battery for a voltage check.  Also the RAID 1 configuration is no longer there (embedded)

Currently I am reinstalling Win 10.

An old problem is resurfacing: the desktop goes into Power Save mode, i.e. the monitor goes off and will not come on when hitting any key on the keyboard.  I had this problem already before the PSU died, and it happened with 3 different monitors.

@GuillaumeCdB -  When you remove the motherboard battery, you reset BIOS to the defaults. For the Studio XPS 8000, the Service Manual says the default SATA Mode is IDE.

It probably was set to RAID for your RAID1, so you'd have to change it back to RAID in BIOS setup. And since you're reinstalling Windows, and BIOS is still set to IDE, you can't just go into BIOS and change it to RAID because Windows won't boot, unless you do the change correctly.

As for those power (wake) issues:
Reboot PC and open Device Manager. Expand list under USB. Double-click each USB entry and click its Power Management tab, if it has one. Uncheck the box "Allow PC to turn off...". Repeat for all USB entries.

Now expand list under Human Interface Devices in Device Manager and uncheck that same box for any HID entry that has a Power Management tab. Exit Device Manager when done.

Next, open the Windows Power & Sleep screen. Click Additional Power Settings. On next screen identify the active Power plan and click Change Plan Settings. On next screen, click Change Advanced Power Settings.

On that last screen, disable Hibernation, Hybrid Sleep, USB Selective Suspend, and PCI Express Link State Management. Be sure to save the changes to the power plan and then reboot.