Boot issues with TX750

[Currency Lad]

Background:

Bought this new PSU late December after reading good reviews to upgrade 14 month old OEM system in order to play newer games at decent framerates/resolution (replaced 500W brandname PSU OEM supplied).

 

Plan to replace existing RAM with PC6400 (or perhaps better) with tight timings and existing GPU with 2x Geforce 8800 class (GT or GTS) in SLI.

 

Also plan to overclock a little once Iv'e done my homework. Please note the system has always run at stock and I have attempted no overclocking to date.

 

The problem:

Shortly after installing the TX750, the system would shutoff without warning even at idle. Thought I had solved the problem by reconfiguring way the fans and DVD drives were running off the molex cable. Haven't had a real chance to give the system rigorous testing due to commitments over the holiday break.

 

Anyway, the other day the system again shutdown without warning and displayed corrupted video upon rebooting. Since it subsequently rebooted without issue I thought no more of it.

 

The next day, however, the system again shutdown without warning. Upon rebooting it failed to finish POST, successfully rebooted allowing me to enter the BIOS setup screen but shutdown after exiting (instead of rebooting as normal). All subsequent attempts to power up system failed. Green LED on motherboard shows it has power but system fails to power up when pressing main power button on case (no beeps, nothing).

 

Please note that, with the exception of the addition of a Zalman CNPS 9700NT heatsink to replace the stock one, the PSU has exactly the same load as was handled by my previous 500W PSU flawlessly for 14 months.

 

I am concerned that the PSU may have been faulty and thus damaged one or more of the components in my system for the following reason:

Although both the 5V and 12V rails were rock solid (at 4.95-4.97V and 11.97-12.03V respectively) the 3.3V rail appeared unstable. It would commence from a cold boot at 3.43V and quickly climb after 15-20mins use to 3.55V when idle. This would steadily climb under load to sometimes 3.6V at peak. Is this normal for this PSU?

 

The only other possibility is that the wrong 4-pin 12V motherboard connector may have been used. The 8-pin EPS12V connector supplied breaks into 2x 4-pin connectors, but the users' manual gives no indication which is the correct 4-pin ATX12V connector to use (although it requests you use the correct one). One of the 4-pin connectors has black stripes running down the yellow wires and, since my old PSU had the same on its single 4-pin connector, this is the one I connected. Was this incorrect? If so, wouldn't a single sentence in the manual avoid the confusion?

 

Anyhow, at the moment I have a dead system. Any ideas?

[RAM GUY]

When you attempt to boot the system do the fans spin up and then the system powers down? Or does the system stay on with all the fans running?

[Currency Lad]

Behaviour when the system would suddenly shutoff was same as for a soft shutdown - all fans/lights etc. off - except without the graceful exit from Windows and would occur without warning.

 

The green LED on motherboard lights up when the rocker switch on the PSU is set to on - all other components including fans are off.

 

Obviously, when the system could attempt to boot the fans would power up. This includes the one occasion when it failed to POST which, however, was immediately followed by a hard shutdown as above - preventing me from being able to read the "failed to POST" error message onscreen.

 

As stated in first post, was able to successfully POST after this and enter the BIOS setup. Upon exiting this, however, a hard shutdown occured. All subsequent attempts to power system on (by pressing the main power button on front of case) have failed - no lights, no fans, no beeps ... nothing.

 

Have checked all connections are OK and couldn't see or smell any obviously burnt out components.

[RAM GUY]

What happens when you try the Paperclip Test? If it powers up and stays on, then I would recommend testing the PSU in a different system, however if it does not stay on, or turn on at all, then we should have it replaced.

[Currency Lad]

OK. Performed paper clip test with 2 fans attached for load and all remained powered and spinning (including PSU fan) as long as there was a connection. I suspected that the PSU was able to supply power per se as the green motherboard LED still came on when the PSU's rocker switch was set to on.

 

Reconnected everything and was able to boot and enter BIOS. Upon exiting, system shutdown instead of restarting. Did a cold boot and managed to load Windows until the system again powered off (hard shutdown as above) after about 1 minute. Subsequent attempts to power up and boot failed with no response as before (fans spin 1/2 revolution, then stop). Bizzare, huh?

 

So, looks like I'm in the unenviable position of having to diagnose an obscure hardware problem/conflict - next candidates to check are CPU, RAM and finally, motherboard. But this leads me back to the point in my original post. That is, these problems did not manifest themselves for 14 months on my old PSU - only when this one was installed.

 

I am seeking answers to the following specific questions:

 

a) Monitoring the 3.3 volt rail when the sytem was able to boot after the paper clip test, I observed its value to be initially 3.31V in BIOS which climbed to 3.36V before shutdown. Upon loading Windows, value was 3.46V and climbing. Had the system not suddenly shutdown, I am certain it would have again settled (at idle) to the 3.55V value noted in original post. Again, is this behaviour normal for this (or, indeed, any) PSU?

 

b) When breaking apart the 8-pin EPS12V connector, which is the correct 4-pin ATX12V connector to use, or doesn't it matter? (Refer original post).

 

c) Is there any interaction between the PSU and the motherboard (eg. readback of voltage/temperature values) that would cause the PSU to suddenly shutdown?

 

RamGuy, if you could kindly address these specific issues in your next post it would be greatly appreciated. Anyone else who may have a clue why the system would behave in this fashion would also receive my gratitude. Regards.

[Currency Lad]

Bump. Anyone? Hello?

[RAM GUY]

I am seeking answers to the following specific questions:

 

a) Monitoring the 3.3 volt rail when the sytem was able to boot after the paper clip test, I observed its value to be initially 3.31V in BIOS which climbed to 3.36V before shutdown. Upon loading Windows, value was 3.46V and climbing. Had the system not suddenly shutdown, I am certain it would have again settled (at idle) to the 3.55V value noted in original post. Again, is this behaviour normal for this (or, indeed, any) PSU?

 

How did you measure the voltage on that rail? Were you using a multi-meter or software monitoring? There's an ATX specification that gives +/- 5%, so from 3.14 to 3.47 the PSU should be fine. If when booting the system the you measure the rail going out of spec, then the motherboard might be drawing too much power and triggering the overcurrent or overvoltage circuits in the PSU, but I would test in a different system to be sure.

 

b) When breaking apart the 8-pin EPS12V connector, which is the correct 4-pin ATX12V connector to use, or doesn't it matter? (Refer original post).

Only one side of the 4/8 pin will fit in the slot on the board, so there is really only one way to install it.

 

c) Is there any interaction between the PSU and the motherboard (eg. readback of voltage/temperature values) that would cause the PSU to suddenly shutdown?

 

If the motherboard pulls more wattage from the PSU then it is supposed to it will trigger the overcurrent or overvoltage protection circuits in the PSU and it will shut down in order to protect the system. Also, if the motherboard detects temperatures that are too high (CPU, Chipset, etc) it will tell the PSU to shut down.

 

Have you tried re-seating your new CPU heatsink?

[Currency Lad]

RamGuy,

 

Thanks for the answers - much appreciated.

 

Yes, you're correct - the value of 3.3V rail was measured in software as reported by the Winbond chip on my motherboard (ASUS M2N32-SLI Deluxe). As such, the absolute value of the readings may be suspect. But what concerns me is the 0.3V climb from initial boot to running at load (3.3V at boot, 3.6V under load). This is the full 10% range allowed by the ATX spec.

 

Not sure where exactly on the board to measure with a DMM and the last thing I want to do is short something out by taking a stab in the dark. ASUS aren't exactly forthcoming with details and have posted question on their forum but so far no luck.

 

The hint about the motherboard drawing too much power may have some merit. Although, I didn't notice the same behaviour on the 3.3V rail with my old PSU (was always reported as 3.35V unvarying) and the 5V & 12V rails on this PSU are solid. Is there something about the design of this PSU that may make it more likely?

 

To eliminate all other variables, I am going to reseat the CPU with the old stock heatsink and see how that goes. I'll let you know.

 

Thanks again.

[RAM GUY]

The hint about the motherboard drawing too much power may have some merit. Although, I didn't notice the same behaviour on the 3.3V rail with my old PSU (was always reported as 3.35V unvarying) and the 5V & 12V rails on this PSU are solid. Is there something about the design of this PSU that may make it more likely?

 

To eliminate all other variables, I am going to reseat the CPU with the old stock heatsink and see how that goes. I'll let you know.

There is nothing in the design of the PSU what would make the 3.3v rail run differently from another PSU, however it is hard to say with confidence that the 3.3v rail is increasing by reading only the software or BIOS measurements, and you would need to measure with a DMM to know for sure. Let us know if reseating the CPU and heatsink makes a difference!