Seasonic SS-600ET Voltages

[LordEricX]

Building a new "Entry Level Gaming" Computer for my Nephew. I tested the Motherboard on my test-bench w/ just a CPU and 1 stick of Memory and got the lovely sound of a "post beep". Installed the motherboard into its new home w/ a new Seasonic SS-600ET power supply. I did a basic test of the power supply looking at the 12v, 5v and 3.3v lines and all were spot on. (something I would expect from a Seasonic power supply) This is where my problems began... The motherboard light comes on and the fan spins but no post. I pulled out the motherboard and put it back on my test bench and had the same issue, no post. After testing the CPU and Memory in a known working computer and getting the system to post, I figured there must be an issue w/ the motherboard or power supply.

Going back to the power supply I tested in depth looking at all of the voltages and came across the "pwr ok" lead giving strange readings. The voltage goes from 2v to 4v erratically.

Is this normal or did it damage my motherboard? What can I do to fix the issue?

 

[Darkbreeze]

The nominal voltage of the Power Good signal is +5 V, but in practice the allowable range is usually up to a full volt above or below that value. I'd bet the motherboard is to blame, but only if taking manual readings from the power supply has indicated all rails and connector readings are within limits. Personally, I'd try to bench it with a different power supply, and if that fails to POST, then I'd RMA the motherboard.

 

[LordEricX]

I understand the voltage on the "PWR OK" is 5v to the motherboard. What i'm trying to understand is if the voltage is an erratic 2v to 4v (A) is this normal (B) if not normal, will this cause damage to the motherboard (C) can the motherboard be saved.

I have a test bench that is a fully working LGA1150 computer. (G3220 CPU, DDR1333 2x4gb, Antec 500w PS, H81 motherboard)

What is in question is the Seasonic SS-600ET power supply w/ the erratic PWR OK voltages and a Asus H97M-E motherboard.

The H97M mother board gave me a POST beep on my test bench but failed to do so connected to the Seasonic PS. Retested the motherboard with the Antec PS and failed to POST.

 

[Darkbreeze]

1. 2v to 4v when it should be somewhere between 4v and 6v, but preferably closer to 5v, is not normal. That's why I indicated a volt in either direction is "ok", but 1 to 3 volts below spec is probably an indicator of a problem.

This is pretty unusual for a Seasonic unit, so I'd recommend that your RMA the unit and explain to them what the problem is. I doubt that an undervolted signal on the power ok circuit would cause any trouble to the motherboard. Worst case scenario, unless there is ACTUALLY something else wrong with the unit, would be that the motherboard simply wouldn't power up.

There is never really any "saving" a motherboard. If it's damaged, it's done. If it's not, then it's ok. Pretty much as simple as that even if you have electronics repair experience, there is relatively little on a motherboard that can be replaced or repaired without astronomically expensive automated equipment.

IF the motherboard fails to post when using another, unrelated power supply, then either something that you've kept onboard like the CPU, RAM or GPU card is the culprit, or the motherboard is indeed bad. Eliminating all common hardware by removing what's not needed to be connected such as drives etc. and swap in a different CPU if one is available or try different RAM. This:

http://www.tomshardware.com/faq/id-1753671/bench-troubleshooting.html


If you are already familiar with those procedures and have done them, and still don't know what the problem is, then I'd just replace the motherboard and RMA the PSU. Certainly one can take out the other any day of the week, even under the best of conditions and using the best of hardware. Sometimes there simply is no "this IS the problem" way to determine what the issue is and you just have to throw parts at it. Not usually, but there are times.

 

[LordEricX]

I agree w/ you 100% that voltages below 6v on "PWR OK", even if they are erratic, should not damage the motherboard. Stripping the system down to the CPU, 1 stick of Memory and a known good PS I do not get a POST beep. I've done everything I can think of... 3 different CPUs, different sets of Memory, Clear CMOS and pissing on a sparkplug. Makes me sad to the fact I have to return the H97M-E/CSM motherboard and get a refund, because the place I got it from is out of stock and is unknown when they will get more.

Thank You for your help. Best Solution chosen.

 

[Darkbreeze]

pissing on a spark plug.

Ha! I thought I was really about the only person who used that phrase. Guess that's probably since one of the hats I wear is as a long time automotive tech and self employed shop owner. Too funny. I'd have to agree that the most probably failure would be the motherboard. Seems like it's actually becoming a more consistent issue these days, even with high end boards. Anyhow, good luck to you Eric.