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Problems with two TX650s


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In May 2008, I put together two nearly identical systems that consist of:


- MSI K9a2 Neo-F (AMD 770)

- AMD Phenom 9550 2.2ghz (not overclocked - reliability is the priority)

- Xigmatek HDT-SD964

- Corsair TWIN2X4096-6400C5 DDR

- Nvidia 7600GS (in system # 1)

- Nvidia 7900GS (in system #2)

- Corsair TX650 PS

- WD Caviar 160gb SATA

- Maxtor 120gb IDE (leftover from previous systems)

- Pioneer DVD

- ADS Firewire card

- Cooler Master Stacker case

- XP 64, latest SP and autoupdated


I consulted some online PS calculators before selecting the TX650s. Based on the config above, a single rail 650 watt PS is way more than enough.


Up until recently, both systems ran with absolutely no problems.


Two weeks ago, one of the systems hung during a normal shutdown I initiated. The system hung at the point in the shutdown just before it actually powers off (blank screen that's the color of the desktop). I reset the system but it wouldn't successfully boot. Fans would spin, power light would be on - but no post beeps or anything. Repeated attemps resulted in the same thing.


Long story short: I solved the problem by not powering a supplementary 90mm case fan via the motherboard (it's been a few days and I haven't seen anymore problems with that PS). This really puzzles me. Why all of a sudden did I need to reduce a few watts of load to the motherboard?


Two days ago, on the other (nearly) identical system, I was in the midst of encoding a DVD when the display went blank. Fans were still going, but the lack of any disk activity told me the system was effectively dead. I reset the system and the same thing happened as with the other system: fans on, no post, no beeps.


Long story short: Couldn't get the system to post if everything was installed. This system uses a Nvidia 7900GS display card. If I swapped-in a 7600GS (uses less power), then it booted. Weird. Tried the 7900GS in a buddy's system: worked fine. Double weird. Ended up replacing the TX650 in the system with a 750 watt PS. Problem(s) solved.


So, I'm trying to understand what's going on here. I bought two TX650s (at the same time) to power two nearly identical rigs. They work great for several months and then, within the span of some days, both power supplies seem to be acting as if can't provide the rated amps.


BTW: I'm an experienced system builder. I did indeed do all the typical stuff when debugging the system problems: test with everything removed except the CPU and one stick of ram, test with the MB & PS out of the case, test components in other systems, tear everything down and completely reassemble, etc.


So, should I RMA both of my TX650s?




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Yes, each system is powered via its own APC BackUPS 750 UPS. I tested each outlet the UPSs are attached to and they are OK. They're standard grounded outlets and ground appears to be fine.


I ran some tests to see how much power each system is actually drawing (amp meter between UPS and PC). Even under heavy load (prime test), the PCs draw no more than 1.56 amps (184 watts). Utility power voltage has seemed fine, always floating between 119 and 120 volts whenever I check it. Our area does go through periods when there's sags in the utility voltage. I've seen it go down to 108v for a few days. However, I've seen no problems with utility voltage over the last few months.


Both systems have MSI k9a2 NEO-F motherboards, running Phenom 9550s. My BIOS settings for CPU and mem were effectively all set for auto. In the course of debugging things, I noted that the BIOS was running the CPU at less than 1.2 volts - around 1.14 - 1.18 volts. Seemed low to me since the specs I have for these CPUs list 1.2 or 1.25 as the typical voltage they should run at. I don't run Cool'n'Quiet. A couple days ago, I set the BIOS on both systems for a CPU voltage of 1.25 volts. Haven't had any problems since then.


So at the moment, I have both systems working again. The system with the 7900GS graphics board now has a PCP&C 750watt power supply (replaced the TX650). The system with the 7600GS still has its orginal TX650. Systems have been running fine since my original post. I'm clueless what was really the cause. But I'm up and running again.




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BTW: the systems didn't fail simultaneously. The system with the 7600GS graphics card failed first. The system with the 7900GS graphics card failed 3 days later. I know, it's odd. You'd think the the system with the 7900GS would go first.




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Generally a PSU will either work or it will not, intermittent problems would usually indicate some other issue. If at any point you would like to try replacing the units we can definitely do that for you, but at this point I would suspect the issue lies somewhere else. If you haven't tried it yet, I would hook up the TX650 which was removed from your 7900GS system and swap it into your other system to see if any of the problems come back. Also, you may want to run http://www.memtest.org on each system just to rule out any type of memory related issue.
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