Vertigon
1 Copper

XPS 400 - Trick to boot with broken power switch?

Hi all:

    I have an old XPS 400 that I have sitting in a corner as a media server.  It works great for that purpose, and I usually leave it on for weeks at a time with no monitor attached.

    Recently after trying to reboot the machine,  the power button went "mushy"...  like some physical component in the switch broke.  The system still has power but I have no way to boot it.

    I took the front off and tried pressing the lever mechanism attched to the switch directly, but no luck either.  It sounds like the typical action is to replace that entire I/O board from the front of the machine, but all I need to do is boot the system *once*, set it to boot after power failure in the BIOS, and all should be great.

    This isn't a machine I'm very worried about and it's way out of warranty, so I've been trying to act on some advice I heard which is to (carefully!) short out the particular pins on the I/O connector that tells the mobo to boot.  If I could find the pinout information I might be able to do that.

Any advice on (low-cost) actions I can take, or can anyone point me to any pinout information on the I/O connector?

Thanks!

 

0 Kudos
6 Replies
7 Plutonium

Re: XPS 400 - Trick to boot with broken power switch?

Pinout of the I/O panel is not forthcoming, not posted or given out by Dell any model.

The ATX paperclip grounding of the green wire to black wire with a normally open push button would work.

First, the switch makes momentary contact.

This means that a toggle-type switch will generally not work as a replacement power switch unless it’s also momentary.

Second, the switch is normally open, also known as push-to-make.

When you select a momentary switch, be aware some are normally closed, or push-to-break.
Third, the current carried by the ATX power switch is very low, so you may select almost

any switch you like without regard to the current rating.

This also means you can extend the wires to your power switch using inexpensive hookup wire.
Fourth, the voltage carried is no more than 5V, so you don’t need to pay attention to the voltage rating.
Fifth, the minimum switch you need is SPST (single-pole, single-throw), but any of the other

switch types can be connected to act as a SPST switch, simply by selecting the correct two leads.

24-pin ATX12V 2.x power supply connector
(20-pin omits the last four: 11, 12, 23 and 24)
ColorSignalPinPinSignalColor
Orange +3.3 V 1 13 +3.3 V Orange
+3.3 V sense Brown
Orange +3.3 V 2 14 −12 V Blue
Black Ground 3 15 Ground Black
Red +5 V 4 16 Power on Green
Black Ground 5 17 Ground Black
Red +5 V 6 18 Ground Black
Black Ground 7 19 Ground Black
Grey Power good 8 20 Reserved N/C
Purple +5 V standby 9 21 +5 V Red
Yellow +12 V 10 22 +5 V Red
Yellow +12 V 11 23 +5 V Red
Orange +3.3 V 12 24 Ground Black
  • Pins 8, and 16 (shaded) are control signals, not power:
    • Power on is PULLED UP to +5 V by the PSU, and must be driven low to turn on the PSU.
    • Power good is low when other outputs have not yet reached, or are about to leave, correct voltages.
  • Pin 13 supplies +3.3 V power and also has a second power good sense wire.
  • Pin 20 (formerly −5 V, white wire) is absent in current power supplies; it was optional in ATX and ATX12V ver. 1.2, and deleted as of ver. 1.3.
  • The right-hand pins are numbered 11–20 in the 20-pin version.

Four wires have special functions:

PS_ON# or Power on is a signal from the motherboard to the power supply. When the line is connected to ground (by the motherboard), the power supply turns on.


Report Unresolved Customer Service Issues
here

I do not work for Dell. I too am a user.

The forum is primarily user to user, with Dell employees moderating
Contact USA Technical Support






Get Support on Twitter @DellCaresPro

0 Kudos
Vertigon
1 Copper

Re: XPS 400 - Trick to boot with broken power switch?

Thank you for such detailed information.  Forgive me if I make a novice mistake in interpreting it.

I bridged pins 15 and 16 on the connector from the top so that it could remain on the motherboard.  It did work somewhat, because the power supply, fans,  and CD drive were powered, but the system itself did not boot.  I still assume that the mobo needs the switch signal via the I/O cable to actually kick off the boot.

Remember I don't really need to install a switch, but would installing one change my results in any way?  It feels like there's still something missing here.

0 Kudos
7 Plutonium

Re: XPS 400 - Trick to boot with broken power switch?

It has to be a momentary button that is normally OPEN.  

SPST MINI MOMENTARY

SPST MINI MOMENTARY PUSH BUTTON SWITCH


Report Unresolved Customer Service Issues
here

I do not work for Dell. I too am a user.

The forum is primarily user to user, with Dell employees moderating
Contact USA Technical Support






Get Support on Twitter @DellCaresPro

0 Kudos
seaduner
1 Copper

Re: XPS 400 - Trick to boot with broken power switch?

This is a year old post about turn on an ATX supply, so I'm not sure the author is still monitoring this.  Seems like good info, but this doesn't work, as stated by a previous posts. This momentary connection of the green to black only turns on the PSU fans for me.  It doesn't boot the system.  It appears something else is missing. Interesting enough, the author says to use a momentary switch between the green and black (ground) wires, but his video and illustration shows a paperclip inserted for a constant connection, not a momentary connection.  So the instructions don't match the demonstration, which is a clue that something has been overlooked in the directions.

0 Kudos
Vertigon
1 Copper

Re: XPS 400 - Trick to boot with broken power switch?

Yeah, unfortunately this trick did not work for me.  He did say I think that the paperclip would have to be replaced with a momentary connection, but even with the specific switch he suggested I had no luck.  I tried some other methods but I eventually messed up the power supply, so I ended up abandoning the project since it was just an old PC I was only using as a media server. The infuriating part is that the PC was fine, the power switch was just over-complicated..

0 Kudos
7 Plutonium

Re: XPS 400 - Trick to boot with broken power switch?

The power switch is probably mounted on a circuit board, so you may need to replace that to get this to work. And there's always Dell Spare Parts.

Ron

   Forum Member since 2004
   I am not a Dell employee

0 Kudos