Blinking green light on motherboard - what does it mean?

[Wester547]

I'm wondering what it means if, after turning off a computer and turning off the power strip to which the PSU cord is connected, that the green light on the motherboard (that indicates 5VSB power is being supplied) flashes a few times after the light itself shuts off? I would think this insinuates a short of some sort, which worries me...

The system I speak of is the one I referenced in the first thread I created here. The motherboard is a D845PEBT2 and the power supply is an Hipro P3527F3. As stated before, the CMOS battery is dead. Does that have anything to do with it? ^^; This issue didn't arise until I installed this power supply, though (after the former Huntkey died, and after the FSP before it started having cold boot issues). Or rather, if it was there before, it certainly didn't come to my notice. Note that the computer in question is definitely in fine and working condition, I'm just wondering if the 'blinking green light' on the motherboard (after complete power off) could forebode danger somewhere down the road. Does this also have anything to do with cutting AC power?

Thanks in advance for any answers.

[ThePCDoctor]

Re: Blinking green light on motherboard - what does it mean?

EVEN after you kill the input line power to the PC, there's still a huge amount of energy stored inside all the PSU and motherboard caps.
The flashes from the green LED just tell you that the stored power level is going down. To do a truly COLD boot, that green light should be OFF completely. Only then, can you be assured of a truly COLD boot.

It's all normal!

Enjoy!

The Doctor

[dmill89]

Re: Blinking green light on motherboard - what does it mean?

^
I'll second that

This issue didn't arise until I installed this power supply, though (after the former Huntkey died, and after the FSP before it started having cold boot issues).

Chances are the Hipro has much larger primary caps than either of those did and thus supplies power on the 5VSB longer when AC is cut. Hipro tends to use 680uf caps in their 300w PSUs while Huntkey and FSP generally use 470uf or 560uf caps in 300w units. Most Hipro's I've seen are very overbuilt (especially old ones) and are excellent PSUs, although they don't always use the best caps on the secondary (Teapo, SuScon, OST, etc.).

[Wester547]

Re: Blinking green light on motherboard - what does it mean?

Thanks again for the responses. That's reprieving to know.

I didn't open up the referenced Hipro (HP-P3527F3) power supply but I did stick a flashlight on one of the side vents and I noticed one large (680uf, as said before me) Teapo capacitor on one of the primaries, rated at 85C. I also might have spotted another Teapo in one of the secondaries. I guess Teapo on the primaries is better than Capxcon, though? (that's what the other Huntkey had, which was closer to being a 350W PSU, I think - it was of the Huntkey V Power 450 series, or a LW-6450HG, maybe, though it was rebranded by BFG as a BFG450GS and had thick heatsinks). Then again, I've read what's on the primary matters less than secondary capacitors in PSUs. But I did open up the older FSP (a FSP300-60BTV), which I think had Teapo (a LXK) on the primaries as well (might have even been 680uf), but one of the Fuhjyyus on the secondaries was bulged and leaking slightly... Not that it was a bad power supply. Save by its capacitors it had great heatsinks, a Pyrotechnic ball bearing fan, and seemed well designed.

Not to be off-topic, though. Glad to know that a motherboard whose light is flashing after total power off isn't necessarily bad.

[dmill89]

Re: Blinking green light on motherboard - what does it mean?

Thanks again for the responses. That's reprieving to know.

I didn't open up the referenced Hipro (HP-P3527F3) power supply but I did stick a flashlight on one of the side vents and I noticed one large (680uf, as said before me) Teapo capacitor on one of the primaries, rated at 85C. I also might have spotted another Teapo in one of the secondaries. I guess Teapo on the primaries is better than Capxcon, though? (that's what the other Huntkey had, which was closer to being a 350W PSU, I think - it was of the Huntkey V Power 450 series, or a LW-6450HG, maybe, though it was rebranded by BFG as a BFG450GS and had thick heatsinks). Then again, I've read what's on the primary matters less than secondary capacitors in PSUs. But I did open up the older FSP (a FSP300-60BTV), which I think had Teapo (a LXK) on the primaries as well (might have even been 680uf), but one of the Fuhjyyus on the secondaries was bulged and leaking slightly... Not that it was a bad power supply. Save by its capacitors it had great heatsinks, a Pyrotechnic ball bearing fan, and seemed well designed.

Not to be off-topic, though. Glad to know that a motherboard whose light is flashing after total power off isn't necessarily bad.

Yah, What is on the primary doesn't matter much in non-APFC PSUs. Capacitance is important but brand means little so long as the brand accurately marks their caps, some no-name brands (Canicon,YC,Anodia,etc.) mark a much higher capacitance on the sleeve than the actual capacitance. Some really bad brands i.e. Fuhjyyu are known to have primaries fail but still at a much lower rate than caps on the secondary.

Teapo is far from the worst brands, and they usually do ok in PSUs. They just aren't one of the best either, they're just mediocre. So far the only failed Teapo's I've seen in PSUs were in hot areas (usually next to/touching coils or resistors) high hours units (most had probably far exceeded their rated lifespan anyway).

[Wester547]

Re: Blinking green light on motherboard - what does it mean?

I've also read that Teapo and G-Luxon (sometime in the early 2000s, but I see dates from 2002-2005) merged. Does that mean that some Teapo capacitors may be closer to being G-Luxon capacitors (I guess it's drudging to tell, but to my knowledge, G-Luxon are not at all well reputed)? I don't doubt that Teapo do okay in PSUs, though the G-Luxon merger might explain why I've seen a number of posts complaining of bulged Teapos after a few year's of use (or give or take a couple), even in PSUs. But I could be wrong, of course.

I've also read that Teapo do alright so long as they're not stressed.

[Wester547]

Re: Blinking green light on motherboard - what does it mean?

Not to bump old threads, but I think I know why the motherboard's green light blinks for a few seconds after I disconnect AC power. It must be because there's 3 amps on the 5vsb rail according to the Hipro label, which I think is hefty for 5vsb, since most other supplies I see only have 2-2.5 amps on it and rather older supplies only had 1-1.2 amps. I don't know how "overbuilt" this PSU is, though, since it's a 300W but only has two 470uF capacitors on the primaries (it can still do 300W, but I'm guessing it will shut down at 350W) and its heatsinks are not particularly thick. However, it does look like it's full of components, so it doesn't look gutless either. I would also think that there's an overspec'd capacitor on the 5vsb rail.

Sort of off-topic, but if there are faulty capacitors on the 5vsb rail, are they more likely to fail high or low (assuming they don't have the plague that the Bestec 1E series did, along with select Antecs), or is that too general a question? Failing high is of course worse and the end of the motherboard...

[joshnz]

Re: Blinking green light on motherboard - what does it mean?

The reason for the flashing is due to the caps charging up after they have been discharged (ac power disconnected)
once the voltage meets the start up threshold of the 5v standby it starts discharging the primary caps again this process repeats in-till the start up voltage can no longer be reached.

All capacitors do this the higher the voltage and capacity the more it occurs.
capacitors that are used in high voltage do it as well and is why after discharging the need to be shorted/low Resistance load across them to prevent recharging and causing injury.

[Wester547]

Re: Blinking green light on motherboard - what does it mean?

That's interesting. I've never seen it happen in any other system, though it could be because the capacitors on the 5vsb rail were probably of lower voltage and capacitance (as you said) so it might have reached occurrence less often (or I might have disconnected AC power less often if at all).