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Help for a semi-dead PC

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8 replies to this topic

#1
JorgeA

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One of my computers is a Hewlett-Packard dx7500 Microtower that I bought on clearance at an unbelievable price about three years ago. I'm running Windows XP Pro, Vista Business x86, and Netrunner 12.12 on it. With an add-on graphics card, it serves mainly (and 24/7) as a participant in a distributed-computing (DC) project, but I've also used it to get a taste of both Linux and XP.

 

A couple of days ago, the computer -- at the time running on Vista -- finished a stage in the DC project and I rebooted into XP to see what updates (Windows Defender, MS Office) there might be waiting for it. I installed the updates and left it on overnight, as usual.

 

The next morning I went into my office and noticed that the computer was turned off. Nobody other than me goes into the office, so I knew that no living being had shut it down. It used to go off and not come back on after a power outage, but for several months now I've had it on a UPS battery so it should not have turned itself off even if the power had gone out (which it had not, in any event).

 

I hit the power switch as normal. Imagine my surprise and alarm when -- nothing happened!! No matter how hard, how many times, or for how long I pressed the switch, it would not come on. Time for Web research and diagnostics.

 

I plugged the power cord into a different outlet. Didn't help.

 

I opened the case and dusted it. (There WAS a lot of dust inside. :blushing: ) No dice.

 

I removed the graphics card. Still nothing.

 

Changed out the CMOS battery. Nada.

 

The only sign of life the PC is giving, is that the green LED at the back of the case, up where the power supply is located, is still glowing. The glow seems to be fainter than it used to be, but I can't be sure of that. However, nothing else seems to be doing anything: neither the fans nor the hard drive appear to be spinning up. There is no POST and no beeps.

 

My Web research seems to point to either the power supply or the motherboard. Two questions:

 

1. Is there any way to test these, to determine which one might be at fault? (Hoping it's the PSU that's having the problem, and not the mobo.)

 

2. Any other possible candidates for being the cause of the problem?

 

What do you think? Any suggestions that might lead to a solution are welcome!!!

 

--JorgeA

 




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#2
dencorso

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Open the case and look for bad caps, just in case (you know, burst electrolytic capacitors).

If you don't see any, then buy or borrow a used but known-working ATX power supply (that computer seems to use a common, garden-variety, 300W el-cheapo power supply, so anything 300W or more should do) and replace the power supply. If the computer springs to life, then you may discard the old power supply and call it a day, or even consider giving your machine a higher-end, new, power supply. If replacing the power supply gets you nowhere, then you do have a problem. My 2ยข only, of course.



#3
Ponch

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Any other possible candidates for being the cause of the problem?

No, the usual suspect here is the PSU.

I'd think a MoBo with leaked capacitors would still show some signs of life, but it may depend on which ones are busted and how bad.



#4
Tripredacus

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If you don't have a power supply tester, you should be able to just hook up another PSU and see if it powers on. You might be able to do this by simply unplugging the current PSU from the board without removing any components... Although I do not know how that looks on the inside. When I do this, I also will unplug the HDDs from their power just so that if the PC does turn on, I can shut it off without having to worry about an OS being in mid-boot.


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#5
JorgeA

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Thanks, guys.

 

I inspected the capacitors (viewed some images on the Web so I'd know what signs to look for) and everything appears normal.

 

@dencorso, you specified I should try a "used but known-working" PSU. In our situation, is that preferable to a brand-new PSU bought at the store?

 

@Trip, just to make sure -- so I would be disconnecting the old PSU but leaving it in place, then on the operating table connecting the new PSU to the motherboard as a test, right? I would connect to it everything that's currently connected to the old PSU, except for the HDD?

 

@Ponch -- this is reassuring. I already had to replace a PSU on a different machine so I have a little experience with the process. (In that case, the LED wasn't even lighting up.) Plus the repair would be a lot less expensive than a new mobo or (God forbid) a new CPU.

 

--JorgeA

 



#6
submix8c

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Yes, in any/all cases. Works for me, anyway.


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#7
JorgeA

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Yes, in any/all cases. Works for me, anyway.

 

Which question were you answering?  :)

 

--JorgeA



#8
Tripredacus

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@Trip, just to make sure -- so I would be disconnecting the old PSU but leaving it in place, then on the operating table connecting the new PSU to the motherboard as a test, right? I would connect to it everything that's currently connected to the old PSU, except for the HDD?

 

I just plug into the motherboard and hit the power button. I guess I flubbed with that part about the HDD, I do then test with everything but the HDD plugged in before going through the trouble of swapping the PSUs out. Basically, it is wasted effort to swap the PSUs only to find out that wasn't the problem.


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#9
JorgeA

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Supposing that I get a new PSU to test, HP has thrown me a curve ball by offering four (!) PSU models, the only difference being that two are "with power factor correction (PFC)" and two are "without" this PFC, whatever that means. Then one of each type (with/without PFC) is "RoHS: COMPLY_2.03" while the other one of each type is "RoHS: COMPLY_2.04".  :wacko:

 

I tried looking up this PFC concept but I couldn't make heads or tails of what they were talking about in the Wikipedia article. How's one supposed to decide from among them??

 

The part number for the PSU (by Bestec) that's currently installed doesn't match any of the numbers on the HP parts list for this computer, so I can't use it to try to match what I currently have. Looking up the PSU by the Bestec model number on Amazon (where BTW it's MUCH less expensive than if bought via HP) didn't solve the PFC/non-PFC mystery.

 

How to choose between PFC/non-PFC, and RoHS COMPLY "2.03" vs. "2.04"?

 

--JorgeA

 






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