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trouble turning the computer on


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#1 HAJiME

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Posted 02 June 2009 - 11:37 AM

I have to press the button over and over until the computer randomly turns on. Appears to be loose connection with the button (which on my Dell dimension is a flimsy thing in the first place), but it seems to be worse when it's been off for any length of time, say overnight, compared to just turning it off and turning it back on now when it turns on straight away. When I'm trying to get it on, the light on the power button lights up and then turns off at random.

Before I phone Dell and have them charge me 30 for a diagnostic test that I'm not entirely sure I trust, I'd like to know what you guys think. :thumbsup: I figure the answer is probably to just buy a new case? At least I could get a smaller one I s'pose, this monster is an echoing joke.

Thanks so much for looking and in advance for any help,

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#2 rigacci

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Posted 02 June 2009 - 01:42 PM

I'm not sure I would blame the case. Due to what you say has been happening, it sounds like some component has a problem when it is cold and once warm, it works "better" but not great.

I would suspect the power supply first. The power supply starts off cold and then gets warm within a few minutes. Within the power supply, there is something called "Power To Good" which is the time it takes for the power supply to get up to proper operating output. Possibly, when it is cold, it takes too long and will not allow it to boot?

On the other hand, you can get a case WITH a power supply for not too bad a price. Just make sure it is a GOOD power supply.


And good luck.



DR

#3 HAJiME

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Posted 02 June 2009 - 01:58 PM

Thanks so much,

Any way to assure it's the power supply without replacing it?

And do you think there will ever come a point where this problem will prevent me from turning it on at all? Or is that unlikely? Just wondering how concerned I should be about suddenly not being able to turn my pc on at all...

#4 rigacci

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Posted 02 June 2009 - 03:43 PM

I have a power supply tester, the most rceent I believe, that gives all of the voltages as well as the "Time to Good". I believe an acceptabel Time to Good is 500ms (milliseconds). The latest power testers have LCD displays and run less than $20 on ebay, but your local repair shop may be able to help althugh you might want to take it out and bring it down there all by itself.

And yes, it will probably get to a point where it just won't work at all.

Good luck.


DR

#5 garmanma

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Posted 03 June 2009 - 11:12 AM

Caution: There are electronics inside the case that are very susceptible to electrostatic discharges. To protect your computer, touch the metal of the case to discharge yourself of any electrostatic charges your body may have stored before touching any of the components inside. As a safety precaution you should unplug the computer to avoid electrical shock.
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The purpose of this procedure is to bypass the motherboard to test the PSU.

Caution:
This procedure will involve working with live 12VDC electrical potentials which if handled improperly may lead to electrical shock. Proper precautions should also be taken to prevent electrostatic discharges (ESDs) within the case of the computer. For safety purposes please follow the instructions step by step.

First, shutdown your computer. Then unplug the power cable going into your computer.

Once you have opened the case, touch the metal of the case to discharge any static electricity.

The connector of the PSU which connects to the motherboard is readily recognizable by the number of wires in the bundle. To disconnect it you will need to press on the plastic clip to disengage it and then pull the connector up and away from the motherboard. Please take notice of the location of the locking tab and the notch on the socket of the motherboard, this will only connect one way as it is keyed. This wire bundle will have a memory of the way it has been installed and will want to bend back that direction, you may have to play around with it to find a position that the connector will stay in the same position while you run the test.

Posted Image

From the top left to right the pins are 13-24, the bottom from left to right are 1-12.


Please notice that there are PSUs with 24 pin and 20 pin connectors, the location of the green wire in the 24 pin connector is #16, and the green wire in the 20 pin connector is #14. If you look at the connector with socket side facing you and the clip on the top the number one pin will be on the bottom left corner. This makes the pin out for the 24 pin connector from left to right 13-24 on top, and 1-12 on the bottom. The pin out for the 20 pin connector from left to right is 11-20 on top , and 1-10 on the bottom. If you look at the connectors you notice that these are sockets that fit over the pins on the motherboard where the PSU cable attaches, this is where you will place the jumper. For a jumper you will need a piece of solid wire about the size of a paper clip (20-22 awg), preferably a wire with insulation. It will need to be large enough to fit firmly into the socket so that it will not need to be held in place while testing. You are at risk of electrical shock if you are holding the jumper when you power up the PSU. Insert one end of the jumper into the socket of the Green wire, and insert the other end into the socket of any Black wire.

Once the jumper is in place plug the cord back in. If the PSU is working properly the case fans, optical drives, hdds, and LEDs should power up and remain on. I would suggest that you not leave this connected any longer than is necessary for safety purposes.

To reconnect the 20/4 pin connector unplug the power cord, remove the jumper, and reconnect the connector. Take a moment at this time to make sure that nothing has been dislodged inside the case.
---------------------------
At this point you can use a DC Voltage meter to read the different rail Voltages. You will want to insert the black probe into any of the Black (-) sockets, and insert the Red (+) probe in the five different colored sockets, one at a time. Below are the five different colors and their corresponding rail Voltages. The Voltages should be within about ten percent of the given values.

Yellow +12VDC

Blue -12VDC

Red +5VDC

White -5VDC

Orange +3.3VDC
Mark
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#6 HAJiME

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Posted 14 July 2009 - 03:28 AM

I'm not confident messing about with the internal workings of the computer, so I guess I'll have to take it to be fixed somewhere.

I don't know if this helps the diagnostic, but the other day after leaving it plugged in ALL day (I live n the uk, so the mains have switches, andi turn them off whennot in use usually), it was still blinking the orange light at me and not turning on. I pulled out the power supply on the back of the computer and plugged it back in, and it stopped blinking and turned on immediately. Today, it mysteriously worked after turning my monitor off and then back on.

Probably coincidence, but could it be possible that it's an issue with shared power? The PC shares an extention cable with the monitor, printer, scanner and speakers. When I next turn it off I'll try giving it it's own mains socket and see if it improves.

#7 HAJiME

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Posted 22 August 2009 - 11:03 AM

Fixed!

Just an update in case anyone encoutners this issue in the future. I changed the entire power supply (it cost me 23 and my friend fitted it for me) and now it works as normal.

Strangly, before changing it, I found that unplugging all the USB devices allowed me to turn it on much quicker.

Thanks for all the help.

Edited by HAJiME, 22 August 2009 - 11:04 AM.





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