# Dell Dimension 9100 - bad power switch?



## IFP (Mar 10, 2009)

Hello all - first time poster here.

My Dell Dimension 9100 refuses to power up - no blinking amber lights or diagnostic lights/beeps of any kind, no fans, nothing.

I've confirmed that the power cable and power outlet I'm using are all fine, and in fact the little green flea light comes on when I plug it in.

My first suspiscion was the PSU, but now I wonder... I've been told that pressing and holding the power button should discharge all flea power within 5-10 second - does that mean the little green light should go out?
Because I can press and hold the power button for as long as I want, the green light doesn't go out for 2-3 minutes... whether I'm pressing the power button or not. Could my problem just be a bad power switch?

Thanks in advance for any advice!


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## Wrench97 (May 10, 2008)

Do you have access to a digital volt meter?
Have you removed the side cover and followed the wires from the case switch back to the motherboard?


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## IFP (Mar 10, 2009)

I don't have access to a volt meter, but I'm guessing that I could check the voltage coming from the PSU?

Following the wires from the switch to the motherboard on this PC is a bit of a problem - the switch is part of a small I/O panel on the front, which includes USB ports, and the entire I/O panel is connected to the board with a large ribbon cable - I'm clueless as to how to actually check that, other than just making sure it is seated firmly at both ends...


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## Wrench97 (May 10, 2008)

Making sure it's seated is what I was going to say.
With the Volt meter you need to make sure you have 5v standby at the motherboard power connector purple wire and the green PS_ON wire is at 3- 5v and drops to 0 when the power switch is pressed.


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## Wrench97 (May 10, 2008)

Making sure it's seated is what I was going to say.
With the Volt meter you need to make sure you have 5v standby at the motherboard power connector purple wire and the green PS_ON wire is at 3- 5v and drops to 0 when the power switch is pressed.


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## IFP (Mar 10, 2009)

This green PS_ON wire that you mention - is it part of the 24 pin power connection on the motherboard? And will I actually be able to test the voltage on these while they are connected to the board?

I'm still wondering about the green flea light - should it go out when I hold down the power button for 5-10 seconds?


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## Wrench97 (May 10, 2008)

With the power unplugged normally but it's not a good indication.
Yes you check the power with the power connector plugged in both wires are on the 34 pin main connector. If for example the purple wire has 5v and the green does not then you would unplug the I/O panel connector from the motherboard if the green then has 5v the switch is stuck closed or the wires are shorted, you could then jump the green wire to a black ground momentarily with a paperclip or short jumper wire and the pc should start. but first you have to know the readings now.


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## IFP (Mar 10, 2009)

Ok, so it sounds like I should get a volt meter before I just assume anything and start wasting $$. Anything special I should now about meters? Will just walking into Radio Shack and asking for a basic volter meter do the trick, or is there a specific type I need to look for?

Thanks a ton for your help!


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## Wrench97 (May 10, 2008)

Sears has a decent one for about $20 and they come in handy for other adventures around the house and garage.
http://www.sears.com/shc/s/p_10153_...hop&sName=Multi-Meters,+Testers+&+Accessories


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## IFP (Mar 10, 2009)

Thanks - I'll be grabbing a meter today. One question I just thought of - this is a Dell, bought in 2005 - I saw on the "how to test" page that some Dells have proprietary PSU/motherboard combinations - does that apply to mine? Is there a way to tell?


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## Wrench97 (May 10, 2008)

No the wiring is standard the only thing that may be an issue is the placement of the 110v connector on the PSU some models interfere with the side of the case opening slightly requiring a little trim of the case other models go right in.


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## IFP (Mar 10, 2009)

Well, the strangest thing has happened.

I got a multimeter, and started testing the ATX connector while connected to the motherboard, with AC power plugged into the wall. I was following the ;how to test...' instructions here on this site.

So, Pin 9 shows 5V, as it should.
Then Pin 14 PS-On shows 4.09V - ok, that's in the normal range.
Then I press the power button, but the voltage on PS_On does NOT drop to 0 - so OK, it's either my switch or my CPU. Hopefully switch.
So then, I "jump-start" by shorting PS_On to GND, and the computer starts up.
Sweet!
It doesn't boot though, because I had disconnected the IDE ribbon cables to get better access to the ATX connector.
So, I push the power button again, and it power down without issue.
Weird... the power button will turn it off, but not on?

So, after re-connecting the IDE ribbon, I try the power button again - and it starts, no problem. And it's been fine since - I'm posting from it now.

So, now I wonder, should I be worried about why this all happened in the first place? Any idea what my problem could have been?

Anyway, thanks again for the help!


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## Wrench97 (May 10, 2008)

It may be a loose connection on the I/O header on the motherboard or the power connector keep an eye on it if it happens again you know where to look first


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## vonhinkle (Oct 15, 2010)

I just had this exact same problem with a Dell Dimension 9100. I used a voltmeter to test the voltages on the wire that they direct you to test above, and had the same outcome. So I jumped the wires as directed and BAM the comp started. Thanks for the advice.

I also found this useful - [url]http://support.dell.com/support/edocs/systems/dim9100/en/SM/techov.htm#wp1053958[/URL]


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## IFP (Mar 10, 2009)

It's funny, I still use the Dell I was asking about at the start of this thread, and it powers on and off just fine UNTIL I unplug the power from the wall (or the power in the apartment goes out, or the power is interrupted for whatever reason.) EVERY time the power is disconnected from the computer, I HAVE to jump-start it to get it to power on. Does anyone have any idea why the power button would not work after disconnecting (and reconnecting of course :wink power to the PC? I worry that one day the jump might not work


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## Wrench97 (May 10, 2008)

It's probably the power supply, not supplying enough power on the 5v sb line to start the PC.


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## vonhinkle (Oct 15, 2010)

When i brought the PC back to my friends house I had to jump it there too. It was only unplugged for maybe 15 min. Everybody thought i was soooo smart with the paper clip wrapped in electrical tape to start the comp, thanks for the tip!


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