Troubleshooting a dead PC

I've troubleshot a friend's HP Pavilion P6-2035UK PC and have narrowed down the problem, but I'd like your expert opinions before I get back to him with my diagnosis please.

Pressing the power switch causes the fans to spin up and the power switch to light up, but that's it. No video and no system beep.

The 300W PSU is definitely bad, since it's confirmed as bad on my Thermaltake Dr. Power 2 PSU tester. The display is a solid red, no intermittency.

After checking that the PSU doesn't have a HP proprietary connector, I connected a known good PSU (tested it on the PSU tester first for good measure) but got the same exact result. Note that I didn't connect power to anything other than the motherboard to remove the possibility that something like the HDD is causing this. This PC uses integrated graphics, so there's no graphics card to worry about.

It's just possible that the CMOS RAM is corrupted and hence causing this, so I removed the CMOS battery, but was unable to reset the CMOS RAM since there's no link to do so and I can't find anything about it in the HP documentation.

I wanted to try another DDR3 RAM stick in it, but the only ones I have are in my main PC and I don't want to risk damaging one of those to test it. It's not impossible that the memory is faulty, but it doesn't seem all that likely. Note that the board complained when I removed the module, so it can still detect its presence. The PC also does switch off when the switch is pressed in for 5 seconds.

I visually inspected the motherboard for damage, but it looked perfect, with no dodgy looking caps or other signs.

My diagnosis is that when the PSU died it took out the motherboard with it. It's possible that it's simply a corrupted BIOS that's causing this, but there's no way to reprogram it.

What do you think?

Common HP issue. PSU took out the motherboard.

Mr.Scott said:

Common HP issue. PSU took out the motherboard.

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I concur.

Sounds like a dead mobo, and if the PSU is also dead, it probably took the mobo with it.

Thanks for the confirmations people. It's good to have a second opinion with these things.

Ok, that memory I couldn't troubleshoot due to the lack of a spare part has been bugging me and I wanted to eliminate it as a suspect. Only thing I could do was use my PC, so I took the plunge tonight and swapped it with a stick from my PC. Results:

- My stick in friend's PC: works fine

- Friend's stick in my PC: fans only spin up and no other sign of life, just like my friend's PC.

My PC still works ok after trying that duff memory stick I'm glad to say, but it wasn't a high risk anyway.

I'm glad I tried this now. It's going to be a real cheap fix for a replacement 4GB memory stick.

EDIT: I'm going to replace the PSU too, see post 15 for details.

Yes, PSU failure can ruin motherboard as others have said but not just the motherboard. It can also fry the CPU and memory but damage to the memory is more likely than damage to the CPU IMO. CPUs are very tough and memory is very fragile.

qubit said:

I'm glad I tried this now. It's going to be a real cheap fix for a replacement 4GB memory stick.

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Gazing into my crystal ball, I see you coming back to say a new stick of ram didn't fix it.
I have never seen a bad stick of ram fail to post without at least a beep code...........unless there is no speaker, which is the first tool you should be using for any diagnosis.

Your crystal ball is off again, did you not see that I double verified the fault in the very post you're quoting from?

qubit said:

Your crystal ball is off again, did you not see that I double verified the fault in the very post you're quoting from?

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What do you mean, again?
No. I don't read the posts. I just throw stuff out there hoping I'm right.
Of course I read the post. I'm saying it was a fluke. How long did you run your ram in that machine.....like two seconds?
I'm saying that the machine will fail again when it gets warmed up. There is an underlying issue still there. I hope I AM wrong.....but experience tells me different.

Well, I've been fixing PCs for years too and I have seen enough to know that the mobo works and isn't a fluke. It's a hard fault with the RAM, so was very easy to verify.

That PSU is still iffy though and perhaps should be changed. Note that I initially tested with my spare PSU. I then connected that "failed" PSU from the PC to the tester again to remind myself what exactly lit it up red and it showed that only the power good delay was out of spec. The PC starts up and shuts down just fine with this PSU though, so I'm not sure if it should strictly be swapped out or not. It's quite possible that the PSU had a little spike which took out the RAM and it should probably be changed as a precaution maybe and if it was my money I'd do it. It's 4 years old if nothing else and doesn't look the best quality.

qubit said:

Well, I've been fixing PCs for years too and I have seen enough to know that the mobo works and isn't a fluke. It's a hard fault with the RAM, so was very easy to verify.

That PSU is still iffy though and perhaps should be changed. Note that I initially tested with my spare PSU. I then connected that "failed" PSU from the PC to the tester again to remind myself what exactly lit it up red and it showed that only the power good delay was out of spec. The PC starts up and shuts down just fine with this PSU though, so I'm not sure if it should strictly be swapped out or not. It's quite possible that the PSU had a little spike which took out the RAM and it should probably be changed as a precaution maybe and if it was my money I'd do it. It's 4 years old if nothing else and doesn't look the best quality.

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LOL. Your whole post says it all.

FWIW, I don't have to ask for opinions on a forum to do my repairs.
And I have the proper tools to diagnose. But hey, you've been doing this for years, right?

GL with the repair.

There's always at least one awkward bugger on any forum and in this instance it's you.

I also don't "have to" ask for opinions and I don't normally, but I wanted to anyway this time. Does that meet with your approval? /sarcasm

I also see how you conveniently ignore the double verify and my attempt to discuss the PG state of the PSU with you, Mr Expert. Yeah, awkward and argumentative.

Dude, you're putting a tested, known bad PSU back into a machine that you're spending money on new parts for, and calling it fixed. How effing stupid is that. Tell me.....what do YOU think is gonna happen?
Case closed. I'm out. You know better than I do. I can offer you nothing.

Yeah, I was thinking about that PSU and am getting it replaced with a Seasonic SS-360GP, a pretty high quality unit that doesn't break the bank and is perfect for a basic PC like this with light requirements.

And you need to learn how to speak to people. Your very first post to me tonight was condescending, rude, attempted to put me down and was not helpful in the slightest - just read it again. People like you just crap up other people's threads and are not an asset to a forum where people come for discussion, help and to learn. Yes, please unsub this thread and don't come back. I'd be really grateful.

I call a spade a spade. Period.
Boo hoo if it hurts your feelings.

Yeah, I was thinking about that PSU and am getting it replaced with a Seasonic SS-360GP, a pretty high quality unit that doesn't break the bank and is perfect for a basic PC like this with light requirements.

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Come on......you have no intention of doing this. You're just trying to save face in front of the rest of these fine people here. Your intentions were pretty clear in your other posts.


Enjoy the show Steve.

Definite troll. Now go away.

To credit OEMs, they usually use at least reasonable quality 250 W PSUs and not the falsely labelled no-name crap, which you can usually tell they are right on the spot. The cheap no-name PSUs typically use the 4-diode treatment for the primary side.

HP is more likely to actually use quality tiny PSUs. Delta, Newton and Bestech are usually built well.

And the flaw that I heard about Bestech PSUs were long over with by now, it was with the "250-E" PSUs.
(The 250-E was probably pre-2005)

Badcaps.net said:

Thanks to members everell and severach who did some pretty extensive tests on different Bestec power supplies, so far it seems that only the ATX-250 12E model is the infamous motherboard killer, whereas the ATX-250 12Z, ATX-300 12E, and possibly other ATX-300 models are okay. However, posting pictures of the inside of your Bestec will reveal whether it's from the good or bad models.

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I would trust them more than a CoolMax!

Thanks RJ, that's good to know the quality is better than I thought.

It's tempting to keep using it as it's "only" the power good signal that's a bit iffy which the PC doesn't seem to notice and save my friend money. However, given that the RAM stick was bad, we're not sure exactly why it went bad, the PG is faulty and it's an old-ish PSU at 4 years which has been used for most of that time, it's prudent to change it.

My friend has now ordered the parts from Scan and I'll be fitting them in a few days.