Computer Problem--Help Appreciated

[David Root]

I bought a refurbished Dell OptiPlex 760 small tower CPU about 9 months ago from Newegg. Worked fine until last week, when it started going intermittent on me.

Start up in the morning, works fine then suddenly cuts out, loses all power, and won't restart until left alone overnight.
I took it to a local repair shop, they said it needs either a new power supply or a new motherboard, both of which are too expensive to put in a $300 used machine.
It appears to me that this is likely a protection mode cutout of some kind, as no permanent damage has occurred.
A friend of mine said it could be the microprocessor fan being dead or malfunctioning, so the processor heats up and triggers a temperature sensor to cut the power.
There are still an LED or two no inside the machine even when the power is "off".

I have been on the Dell website and run the "quick" diagnostic test which didn't pick up anything. I am going to try the "full" mode diagnostic test, takes 2 hours, but I thought I would ask you guys first about this. If all it needs is a new fan or a replaced sensor, I wouldn't mind trying that myself, but I would need the benefit of someone's knowledge/experience.

[Gibsonman63]

Sometimes they have a thermal cutoff. Have you tried blowing the dust out of it?

[David Root]

There was a lot of dust in it when I first opened it up. It looks like the repair shop may have dusted it out but I'll try one of my aerosol dusters on it.

[norburybrook]

David, it does indeed sound like a thermal problem. In my experience when power supplies die they just die and then there's nothing. Motherboards can be intermittent before complete failure due to thermal issues.

I've actually witnessed a laptop motherboard being brought back to life by putting it inn the over to re flow the solder . obviously this was a last ditch effort.

I'd remove the heat sink/fan assembly and give it a good clean and then re apply it with some decent thermal compound like arctic silver.


You can download something like CPU temp and check the temperatures of your CPU from inside windows. You'll see if you're in danger territory, also if you go into the bios before the computer boots (press the delete key when booting) you might find a setting with an actually temp reading for shut down. You could disable this or adjust it slightly upwards from the default setting. THis might not be possible with a Dell as they could have their own BIOS and not allow this.


Marcus

[David Root]

Thanx for the tip! Could you explain more on the CPU temperature thing? I don't follow you on that. I am running it with the case lid removed, hoping that might help.

I did blow it out with an aerosol duster and it was pretty clean already.

[Phil_S]

For CPU temp, you'll need to choose something, look here: http://www.tomsguide.com/forum/245467-4 ... monitoring

If your fan isn't running correctly, or your CPU is overtaxed, it will get too hot and stop working. See if that's the problem. It is possible to add a 2nd fan or change the existing one to get more speed. Fans are cheap. It might help if that's the problem.

[xtian]

Do a visual inspection of the e-caps on the motherboard, just like you would on an amp. Look for any leaky or bulging ones.

My computer had a failing power supply--had the same symptom of sudden quit. I replaced the PSU, and all is good. You can get good ATX PSUs for $30-40.

[David Root]

It's been on for seven hours now. I just moved the case a bit to check the caps and it lost the signal but the power stayed on. Shouldn't do that I would think? Caps look OK.

The repair shop I took it to said that no generic PS would connect as the "connections are also proprietary to Dell". Originally they said it might be possible to transfer the guts to another used case that would fit a generic PS, but after further examination they said it wasn't possible.

I downloaded HW Monitor. It shows core and assembly temperatures between 38 and 45 deg C (100 to 113 deg F). Is that OK?

[xtian]

I downloaded HW Monitor. It shows core and assembly temperatures between 38 and 45 deg C (100 to 113 deg F). Is that OK?

Sounds nominal:

http://www.anandtech.com/show/1296/3

[drew]

Is there a Dell part # on the power supply?

[sliberty]

In the old days it was possible to get power supply cable converters for Dell machines in just this situation. Check eBay.

Code: Select all

http://www.ebay.com/itm/Converter-for-Dell-Optiplex-380-580-MB-Mini-24pin-use-Standard-Power-Supply-PSU-/361474531187?hash=item54298f9f73:g:kysAAOSw-zxWosa3

This may or may not be right, but will give you the idea.
[/code]

[David Root]

I could not resurrect it y'day, power is permanently gone, so today I went to Best Buy and got a new one. ASUS K31. Also bought Outlook 2016.

All works great now except I have to rebuild our email address book, and download all my files from my external drive, so I won't lose all that TAG info and my amp build files.

Thanx to all who helped me out on this. Much appreciated!

[David Root]

Sorry double post somehow.