Question System will only turn on when 4-pin CPU-power is disconnected...

Jan 29, 2023
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Hello!

Shortly before Christmas I put my computer in sleep mode only to return from work with all lights out in my home. Apparently my computer made some sort of short that seemed to cause a fuse in my appartment to blow.

Turning on all electricity again made my computer go back to sleep mode (off/orange light on power button). But the computer wouldn't turn on again. Cutting power to the PSU and retrying only turns the fans shortly and the computer does not react or start up.

Now, the system is old (2007) but has been continously upgraded. My PSU, however, is 10 years old and I bought a new one figuring that was the problem. But nothing changed. I have just tried another new PSU/different brand to no avail (700 watts and 600 watts). The current system setup requires around 500 watts of peak power.

I then started changing everything. First the mobo, then the CPU, then swapped all RAM (and also tried without RAM), changed the CPU-cooler, reseated all devices and trying numerous scenarios. I have also tried removing the battery and clearing CMOS. In all cases the graphics card has been disconnected.

The result is the same but I learned that the system will turn on, when the 4-pin CPU-power cable is disconnected. This works in all scenarios but naturally the computer won't boot. Remember, I changed the mobo (a used but working one) and it seems unlikely that this board would have a short circuit as well. I examined both boards with a magnifying glass for bloated capacitators and other signs of shorts etc. Nothing.

I think I have tried all scenarios besides changing computer case.

I'm running out of cooling paste for the CPU but did notice, that not all connections on the CPU have "holes" in them indicating that the pins on the mobo is not connected to all receivers on the CPU. But they never have since this CPU has been in there for 15 years (there would be marks on these seemingly unused receivers).

I have cleaned the computer case at least once a year with new cooling paste but without reseating the CPU. This should keep the pins intact.

Any ideas besides buying a new computer? Anybody solved a similar issue (and I did search Google and tried many of those suggestions)?

Specs:
  • HP m9067SCA (2007)
  • IPIBL-LB motherboard (LGA 775) - changed from native IPIBL-LA a while back because of bloated capacitators
  • Intel Q6600 CPU (have two of those and two Q8200's)
  • 8 GB RAM (4x2 GB Kingston DDR2 800 Mhz)
  • Samsung 840 EVO SSD 250 GB (system only)
  • MSI GTX960 2GB GPU (8 pins aux power) - disconnected
  • Chieftec 650 watts PSU (80 bronze)
Thanks,
Søren
 
Last edited:

4745454b

Titan
Moderator
I really don't mean to be rude, but you have a lot of issues here. First is the general age of that hardware. Add in a power surge with a bad PSU, you really have no idea what might have blown. I don't know what boards those are. I know some boards had issues with 45nm quads, so your Q8200s might not be compatible without a bios update. The 65nm quads like your Q6600 shouldn't be an issue. Finally, 600W and 700W doesn't really tell us anything. I know a "1050W" unit I won't let near my house let alone my system. You need a good quality unit, not something that claims it has a lot of power. FYI, a worst case Q6600 is 105W, and the GTX 960 depending on model maxes out at around 130W. So a system with both needs around 300W. A quality 500W PSU can do this. Depending on model the Chieftec might not have been the worst idea. But I don't know how well the protections, if any, are set or work. if you had a power surge with an unknown PSU in it, it could have passed that surge on to anything.

So what to do? Luckily your system is so old that nearly anything will be an improvement. Try looking around for a new system and just be done with what you have. You'll spend too much time chasing damaged parts.
 
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Jan 29, 2023
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Like I said, the PSU is the oldest component in the case. And the 650 watts did an awesome job for 10 years. I have downgraded the graphics card since this computer is mostly used for office work and old games. 500 watts drain is set high in my opinion.

The IPIBL-LB is with the latest BIOS which allows for 45nm CPU's.

So, you're saying that two new PSU's shouldn't be able to boot a system with the graphics card disconnected? I don't agree - I would at least be able to post with that setup - not only have the fans spin for a second.

I don't think I have a lot of issues with the computer. I have narrowed it down to one issue - the 4-pin CPU power where the PSU obviously cannot be the problem. The mobo was replaced after the power surge with same result.

I just asked here to see if I had missed anything. A new system isn't an option.
 
Some ASUS-made boards do behave like that if the CMOS battery is dead.

There are 3 jumpers on the board and two of them result in no-post: if the ROM Recovery one is missing or the CMOS CLR one is across the wrong pins.

The PSU ticking on then immediately shutting off is a sign that a dead short is detected. That it keeps running if the 4-pin isn't connected suggests it's in the CPU VRM. Check each of the eight Mosfets for continuity between Source and Drain, Source and Gate, and Drain and Gate--if one is shorted, then that is the problem.

The graphics card should be more than disconnected--it should be removed, then the IGP works for sure no matter what is set in the BIOS. Well, if you have a VGA monitor anyway.
 
Like I said, the PSU is the oldest component in the case. And the 650 watts did an awesome job for 10 years. I have downgraded the graphics card since this computer is mostly used for office work and old games. 500 watts drain is set high in my opinion.

The IPIBL-LB is with the latest BIOS which allows for 45nm CPU's.

So, you're saying that two new PSU's shouldn't be able to boot a system with the graphics card disconnected? I don't agree - I would at least be able to post with that setup - not only have the fans spin for a second.

I don't think I have a lot of issues with the computer. I have narrowed it down to one issue - the 4-pin CPU power where the PSU obviously cannot be the problem. The mobo was replace after the power surge with same result.

I just asked here to see if I had missed anything. A new system isn't an option.
Ok, so you have a NEW motherboard, a NEW CPU, NEW RAM, a NEW PSU and it's still not working?
 
Jan 29, 2023
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Ok, so you have a NEW motherboard, a NEW CPU, NEW RAM, a NEW PSU and it's still not working?

No of course not NEW as in MINT. But confirmed working alternate devices. I have not changed RAM since removing all of the sticks result in the same.

After the surge I changed to another mobo which I bought as confirmed working. This board - could - be faulty as well but it is unlikely. Two brand new PSU's - could - be faulty as well but it is highly unlikely. Four CPU's - could - all be dead but also highly unlikely. All in all it is more likely to win the lottery.

I tend to believe it must be the mobo and the MOSFET's. I will double check the CMOS and BIOS jumpers but they are in the default positions.
 
Jan 29, 2023
5
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Some ASUS-made boards do behave like that if the CMOS battery is dead.

There are 3 jumpers on the board and two of them result in no-post: if the ROM Recovery one is missing or the CMOS CLR one is across the wrong pins.

The PSU ticking on then immediately shutting off is a sign that a dead short is detected. That it keeps running if the 4-pin isn't connected suggests it's in the CPU VRM. Check each of the eight Mosfets for continuity between Source and Drain, Source and Gate, and Drain and Gate--if one is shorted, then that is the problem.

The graphics card should be more than disconnected--it should be removed, then the IGP works for sure no matter what is set in the BIOS. Well, if you have a VGA monitor anyway.

I will double check the jumpers. I can see 4 MOSFET's circled in red - where are the other 4?

IPIBL-LB

The graphics card is removed not just disconnected.
 
In the photo I linked to, there are two more Mosfets above the CPU socket to make it a 3-phase VRM for the CPU. And two more below left of it that may power the chipset or something--these have no associated choke so aren't part of the CPU VRM, but from the traces might also be powered by the 4-pin connector so it would be good to check those too.

I also see 4 Mosfets for the PCIe and PCI slots, plus 4 for the memory but those appear to be connected to the 24-pin.
 
Jan 29, 2023
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Since everything besides the board has been ruled out I have bought a new used board (guaranteed to work). I don't have the skills to do the soldering so I have returned the defect board. Keep your fingers crossed!

Can a PSU fry a board (VRM) by over- or undervoltage even though the PSU has these built in safeties?