Optiplex 780 SFF Random Shutdown+ PSU upgrade

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nickrios424

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Oct 28, 2017
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Hello. I have a Dell Optiplex 780 Small Form Factor that has been shutting off at random, usually after about an hour of use, for maybe a day now. Nothing particular seems to cause it, as it happens regardless of whether it is running something particularly taxing or simply idle at the desktop. I suspect a PSU failure, but I’m not sure what exactly is causing it. No burning smell.
CPU- Core 2 Quad Q9550
RAM- 3 2gb 1333 Nanya, 1 2gb 1333 Samsung. (8gb total)
Graphics Card: GT 620
Everything else, including the power supply, is stock. Any idea what could be causing this?
Also, I do not have an optical drive, so could I replace the power supply with another TFX-form factor one without the divot? Or am I just better off replacing a similar PSU?
Thanks for reading. Please don’t tell me not to replace it at all or to get another computer, because this one is all I can do. I see a lot of that in threads about upgrading SFF Optiplexes.
 
Solution
W
Discoloration in the notches on top of the caps is a sign of failure. The notches are there so the cap will leak instead of bulging and then exploding, so it's the same problem.
I have had a malware called Fake Alert that minicked PSU failure. You could try running from a Linux live DVD in Trial mode and see if it still shuts down. It will boot w/o an HDD connected so it's the cleanest SW environment you can have. CC Cleaner had a virus recently so even good sites can be infected. User reviews are not the same as a professional PSU test. A low quality PSU can damage other components over time and it won't be obvious what the cause is. Also users may post the review after only a few days use. The PSU that you have now is protect ing...
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Aftermarket PSUs for that computer saying they make 400W are bogus. Don't buy one unless you see a test or review from a repuatble source that it's a good one. The Dell PSU is a good part, they can get old and fail, but they don't catch fire or damage the rest of the computer. Is there any BSOD or does it just quit?
Before getting a PSU you could inspect the capacitors on the MB for leaks. This will show up as discoloration on the top or out the bottom. If the MB is failing the PSU can shut down due to that. So the PSU swhotting down isn't necessarily the PSU failing. I would also run a good virus scan, and Malwarebytes Anti Rootkit (which was a free beta last time I looked).
 
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Seasonic is a very reputable brand. thanks for posting that link.
It also has 16A on the 5V. rail a place where many otherwise good aftermarket PSUs fall short for use in a Dell.
It even looks like it has the slot in the side that Dell uses to support their PSUs in the case.
 
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I don’t believe it’s any kind of malware. I haven’t downloaded anything other than Windows and a couple of applications from reputable sources. There’s also no blue screen- it just cuts out as though I’d unplugged it. After a moment or 2 it turns back on, and goes into a recovery screen. I have to disconnect and reconnect the hard drive to get it to go into Windows. I decided to dust it to see if there was any kind of interference from dust, but it’s still cutting out. I did notice discoloration on a few of the capacitors but no bulging or distortion.
 
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So, I'm thinking about getting this one. https://www.outletpc.com/wr4972-replace-power-rp-tfx-420-tfx-12v-420w-psu.html From the reviews I've read, it's a good PSU, despite its strange problems with labeling. It's got all the correct connectors. The only problem seems to be the form factor. I want to make sure that the 780 is large enough to fit it. I'm not worried about cable location or about dealing with Optical Drives since I don't have one. Any ideas?
 
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Discoloration in the notches on top of the caps is a sign of failure. The notches are there so the cap will leak instead of bulging and then exploding, so it's the same problem.
I have had a malware called Fake Alert that minicked PSU failure. You could try running from a Linux live DVD in Trial mode and see if it still shuts down. It will boot w/o an HDD connected so it's the cleanest SW environment you can have. CC Cleaner had a virus recently so even good sites can be infected. User reviews are not the same as a professional PSU test. A low quality PSU can damage other components over time and it won't be obvious what the cause is. Also users may post the review after only a few days use. The PSU that you have now is protect ing either itself, or your other compnents by shutting down, cheaper ones don't always do that.
http://www.jonnyguru.com/modules.php?name=NDReviews&op=Story&reid=71
 
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Solution


This power supply is not a true 420 watts

it offers +12V/14A thats total of 168 watts only on 12V.

when you see a cheap $29 power supply never buy one .

to know the TRUE power , allways look at the 12V Ampere , because this is what the PC uses the MOST.

you dont need alot of 5V and 3.3 V ...
 
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Dell Optiplex uses the old BTX form factor that dates back to Pentium 4 days. They do use 5V. and 3.3V much more than later computers. I've solved a few Dell PSU questions by pointing this out. It doesn't take a lot of 5V. Watts to add up to a few Amps.
I would advise looking for a genuine Dell PSU rather than get that one.
 
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