only 4V on standby - EVGA 850 B2 SuperNova

[luvtrumpsh8]

Hey guys I'm looking for a quick tip from a pro to get this fixed as soon as possible. With the info I have it should be a fairly easy diagnose.

I overloaded a 850 EVGA and it got real hot and made a loud pop. I'm wondering what component I blew. It shut down and now it only has 4v on standby and not enough to start it up. So running ok - to getting hot when I added 2 400w video cards, then pop about 45 mins later and now no power on and only 4v on stby.

Good news is I have a second one for parts. Just looking for a head start to get up as soon as possible. Fuse is obviously ok as there is some power.

[luvtrumpsh8]

Re: only 4V on standby - EVGA 850 B2 SuperNova

What makes a pop in a power supply ? Souded like a finger pulled out your mouth but louder.

[budm]

Re: only 4V on standby - EVGA 850 B2 SuperNova

Did you at least open it up to do visual inspection?

[R_J]

Re: only 4V on standby - EVGA 850 B2 SuperNova

Usually the standby is a seperate circuit in the power supply, I suspect you blew the main power supplies fets. at the least

[luvtrumpsh8]

Re: only 4V on standby - EVGA 850 B2 SuperNova

Did you at least open it up to do visual inspection?

Yes of course, nothing out of the ordinary. No burn signs and the fuse tests ok. I can't actually see it as its covered in shrink wrap but there is continuity

By standby I mean the poweron wires, I'm thinking TV where its usually called standby but this is a ATX power supply so it S PB or something.

[luvtrumpsh8]

Re: only 4V on standby - EVGA 850 B2 SuperNova

Usually the standby is a seperate circuit in the power supply, I suspect you blew the main power supplies fets. at the least

This is a difficult power supply to work on. Its all black and tight inside. you can't even see if there any burn marks.

[momaka]

Re: only 4V on standby - EVGA 850 B2 SuperNova

By standby I mean the poweron wires, I'm thinking TV where its usually called standby but this is a ATX power supply so it S PB or something.

Standby and PS-ON are two very different things on an ATX PSU.
Standby provides 5V to the board at all times. It is pin #9 on a 24=pin ATX connector.
PS-ON is what the board pulls low to signal the PSU to turn on the main power supply (3.3V,5V,12V,-12V). It is pin #16 on a 24-pin ATX connector.

Forget about the PS-ON pin for now and focus on 5VSB. What voltage do you measure on the 5VSB pin relative to ground?

As for the popping... that might have been a rectifier/FET on the secondary side.

When you pull PS-ON to ground (i.e. try to jump-start the PSU), does the fan twitch?

[luvtrumpsh8]

Re: only 4V on standby - EVGA 850 B2 SuperNova

The 5V SB is only 4V

That is what I meant by standby.. Its actually the power on button .

[luvtrumpsh8]

Re: only 4V on standby - EVGA 850 B2 SuperNova

Here are the results

pin #9 is 5.12v

ping #16 is 4.02v

Fan doesn't spin but then again it doesn't spin during normal power up either. It only spins after running the psu for a couple of minutes.

[luvtrumpsh8]

Re: only 4V on standby - EVGA 850 B2 SuperNova

Some progress. I stuck a flashlight and cam in there and it looks like Q301 was the pop. Its a 5R 199P / HRA 409

[momaka]

Re: only 4V on standby - EVGA 850 B2 SuperNova

The 5V SB is only 4V

That is what I meant by standby.. Its actually the power on button .

Here are the results

pin #9 is 5.12v

ping #16 is 4.02v

Okay, just to clear some terminology out of the way so we don't get confused in the future:

Standby power = 5VSB ----> this is pin #9
power ON button = PS-ON ----> this is pin #16

What I am seeing by the above measurements is more or less normal. 5VSB should be 5V, which you have. And the PS-ON pin has 4V, which is not necessarily bad (some PSUs have rather low PS-ON signal).

This means the issue is somewhere with the main power supply, so we need to further investigate that...

Fan doesn't spin but then again it doesn't spin during normal power up either. It only spins after running the psu for a couple of minutes.

Try connecting a regular fan to the PSU. Or connect the PSU to the PC and watch the case / CPU fans as you press the power switch. Do the fans twitch?

- If yes, the PSU probably has a short-circuit on one of the rails somewhere on the secondary side

- If no, then it could be that the APFC diode or switchers took a jump. Or could also be the switching FETs blew. Either way, you will not always see a visible burn marks when these go, though sometimes the MOSFETs may split/crack their cases slightly or they may have small holes blown through them - which is what makes them hard to see when they go bad.

*EDIT*
You beat me to it with the above post while I was typing this.

There you have it! -A blown MOSFET. Just need to tell us if it's on the primary side or the secondary, so we can go from there.

[luvtrumpsh8]

Re: only 4V on standby - EVGA 850 B2 SuperNova

EVGA 850 B2 SuperNova

[luvtrumpsh8]

Re: only 4V on standby - EVGA 850 B2 SuperNova

What do you guys think of this ? Its got 0 ohms on every pin in every direction. I think that means its blown right. I just want to make sure its bad and not sure if that is melting on it or a secret sauce compound the mfct puts on to hold on the pin sleeve in place. I'm just stumped because the other one looks the same so they are either both blown or both have compound and the problem is elsewhere.

It was a pain to get to and I had to remove the copper coil because they hide the screw behind it.

[luvtrumpsh8]

Re: only 4V on standby - EVGA 850 B2 SuperNova

pic attached 5R199P

[R_J]

Re: only 4V on standby - EVGA 850 B2 SuperNova

I believe this is the part, IPP50R199CP
If its all shorted, I would also check the gate drive circuit. and order more than one
That is just glue to hold the ferrite beads in place

[luvtrumpsh8]

Re: only 4V on standby - EVGA 850 B2 SuperNova

That is sort of what I as asking, if its blown ? I'm not familiar with mosfets and how to test them but I figured they must have some resistance. All pins seem to be 0 no matter which direction or configuration I try it.

[budm]

Re: only 4V on standby - EVGA 850 B2 SuperNova

If you get 0 OHMS on any combination of the 3 pins then it is bad. Are you sure it is showing 0 OHM since the meter leads will have 0.5~1 Ohm by itself.

[luvtrumpsh8]

Re: only 4V on standby - EVGA 850 B2 SuperNova

it actually shows 1 on the meter but thats just the default of the 200ohm setting. It basically doesn't move no matter which combination of pins I touch and I tried both ways. the meter works because when I test a resistor its pretty close to perfect.

[R_J]

Re: only 4V on standby - EVGA 850 B2 SuperNova

If you short the meter leads together that reading would show a short, if checking the fet and it does not show a short, it could be good and something else is bad.
You should also use the diode test if your meter has it.

[budm]

Re: only 4V on standby - EVGA 850 B2 SuperNova

May be you should read the user manual and study how to use and understand what is being shown on the meter's display means.
Hard to troubleshoot with wrong data.