Corsair GS800 Power Supply Problem

[ShortCircuited]

Re: Corsair GS800 Power Supply Problem

Feedback winding continuity.
Primary open.
Neg side of primary winding to feedback is 11 megaohm.

[R_J]

Re: Corsair GS800 Power Supply Problem

I would also check the resistance of the primary of the transformer, If you have +377v on D19 cathode, you should also have that voltage on D13 anode, and you do not.

[ShortCircuited]

Re: Corsair GS800 Power Supply Problem

If D13 cathode is 377v and D19 cathode is 377v then Q7 is either turned on or shorted.
D13 cathode connects to Q7 Drain
D19 cathode connects to Q7 Source

Q11 original if I remember correctly. Q7 was sourced from another PS
Removed Q7 and it is not shorted. Yes Q7 does have insulating mounting hardware. I will run an independent bench test on this and see if it is good.

It does appear .19 volts is making it through the transformer to the secondary side for the 12v rail.

Q7:


Q11:

[CapLeaker]

Re: Corsair GS800 Power Supply Problem

I just checked the pictures again and you are correct on the resistor, I also did notice that Q7 and Q11 are different, one is a full pack the other isn’t. There is insulating hardware on Q7, but either it is bad, or Q7 is bad. Do Q7 and Q11 have the same part number?

[R_J]

Re: Corsair GS800 Power Supply Problem

I also see Q7 has an insulating kit and Q11 does not, has it been changed to an insulated mosfet? I hope it's drain is not connected to the heatsink. or is Q11 an original and Q7 been replaced with something else?

[R_J]

Re: Corsair GS800 Power Supply Problem

He is still getting like 0.1v or something, I don't think that would be there with an open gate drive resistor.

R116 is the source resistor for Q11, I wanted to see if it was open or not, turns out it is good.

[CapLeaker]

Re: Corsair GS800 Power Supply Problem

where do you see voltages on the secondary?

He is still getting like 0.1v or something, I don't think that would be there with an open gate drive resistor.

[R_J]

Re: Corsair GS800 Power Supply Problem

Confirmed D13 is as originally tested

D19: Cathode 377v Anode .000

If D13 cathode is 377v and D19 cathode is 377v then Q7 is either turned on or shorted.
D13 cathode connects to Q7 Drain
D19 cathode connects to Q7 Source

[ShortCircuited]

Re: Corsair GS800 Power Supply Problem

I don't understand. "D13*:cathode 377v and anode -.19."
So the voltage on:
the cathode of D13 = 377v
the anode of D13 = -.19?
the cathode of D19 =
the anode of D19 =

I was going to ask for the voltages on Q7 & Q11 to see if the gates had any voltage

Confirmed with retest. D13 is as originally tested.

D19: Cathode 377v Anode .000

Q7 377 on all pins-this is not a mistake triple check. I believe I already changed this one when I was working on this PS before.
Q11:G 5.6v - D -.19 - S .0018

If there was a problem on the secondary side when I applied 12v directly current would have over loaded my testing power supply. All voltages were regulated properly on secondary side. Current during this test was less than 1amp and it was not regulated with one 3.5 , one 2.5 and one 12v fan running. 12v, 5v and 3.3v rails were all present.

[R_J]

Re: Corsair GS800 Power Supply Problem

I think there is either a short on the secondary somewhere or there is a problem with the feedback. If R116 is open there wouldn't be anything at all on the secondary.

where do you see voltages on the secondary?

[R_J]

Re: Corsair GS800 Power Supply Problem

D13*:cathode 377v and anode -.19. *Traced to transformer.
R116: 1ohm (in and out of circuit).

So it looks like you are correct no grounding /switching of main transformer on primary side.

I don't understand. "D13*:cathode 377v and anode -.19."
So the voltage on:
the cathode of D13 = 377v
the anode of D13 = -.19?
the cathode of D19 =
the anode of D19 =
If R116 is good then I suspect the fets are ok, but I don't think they are getting any drive.

I was going to ask for the voltages on Q7 & Q11 to see if the gates had any voltage

[CapLeaker]

Re: Corsair GS800 Power Supply Problem

I think there is either a short on the secondary somewhere or there is a problem with the feedback. If R116 is open there wouldn’t be anything at all on the secondary.

[ShortCircuited]

Re: Corsair GS800 Power Supply Problem

...check the voltage on D13 cathode (white mark) and D13 anode and D19 cathode and anode. D19 anode should be close to 0 or ground, if it is not, check R116 it could be open

D13*:cathode 377v and anode -.19. *Traced to transformer.
R116: 1ohm (in and out of circuit).

So it looks like you are correct no grounding /switching of main transformer on primary side.

[ShortCircuited]

Re: Corsair GS800 Power Supply Problem

I have had the entire heatsink (HS3) out and replaced Q7 it appears. Had this PS for a while now. Did a test with a small fan and these FETs worked it seems or I would not have reinstalled it. The CM6800 (not showing short) is very near on the adjacent vertical board.

LOL I was about to start begging for a copy.

[R_J]

Re: Corsair GS800 Power Supply Problem

I don't have a schematic, I am using your picture of the board. When checkiing voltage on the primary side, use the main filter cap (-) for meter ground, then check the voltage on D13 cathode (white mark) and D13 anode and D19 cathode and anode. D19 anode should be close to 0 or ground, if it is not, check R116 it could be open

[ShortCircuited]

Re: Corsair GS800 Power Supply Problem

Those are likely in the gate drive circuit, they are used to modify the turn on and turn off of the fets during operation. that is normal. Those might be the pfc mosfets, The one (or two) I refered to are (Q11?) the ones that drive the transformer.
Those type of meters (UT61E) being lower cost, will be confused by the 20~40khz high frequency signal that is on the pfc mosfets.

Remember the pfc boost circuit is working. The raw dc voltage on the main capacitor would be 160vdc, but the pfc is boosting it to 380vdc.

There are a pair of 20N60S1s (TO220) physically closer to the main transformer and are labeled Q11 and Q7. You have schematic?

380V

I do have a DSO138, but I can't find it useful for anything. I dont think it can handle the voltage to be of any use here. EDIT: 50v 200khz max.

[R_J]

Re: Corsair GS800 Power Supply Problem

Those are likely in the gate drive circuit, they are used to modify the turn on and turn off of the fets during operation. that is normal. Those might be the pfc mosfets, The one (or two) I refered to are (Q11?) the ones that drive the transformer.
Those type of meters (UT61E) being lower cost, will be confused by the 20~40khz high frequency signal that is on the pfc mosfets.

Remember the pfc boost circuit is working. The raw dc voltage on the main capacitor would be 160vdc, but the pfc is boosting it to 380vdc.

[ShortCircuited]

Re: Corsair GS800 Power Supply Problem

That resistance is ok, the ic gets it vcc when the power supply is working, If there is no +12v then U7 is not the problem. Check the primary switching transistors. It looks like the pfc circuit is working as you have 380vdc, but the main primary switcher is not.
It looks like there are two fets in the primary, have you checked them?

Thanks for the suggestion. These two FETs you mentioned are Q10 and Q15 and are 6R190E6s (TO247 package) for which I cannot find the datasheet so I am consulting a C6 datasheet.

The drains are jumping around erratically between 138 and 172ish according to my DMM (UT61E) on both FETs.

The glass diodes (D37 and D40)s (circled yellow) are both 5.6ohm. Why are D37 and D40 (circled yellow) in parallel with a 4.7ohm resistor? What good are the diodes if they are essentially shorted?

I believe I have the pinout correctly labeled on he two FETs-

[R_J]

Re: Corsair GS800 Power Supply Problem

That resistance is ok, the ic gets it vcc when the power supply is working, If there is no +12v then U7 is not the problem. Check the primary switching transistors. It looks like the pfc circuit is working as you have 380vdc, but the main primary switcher is not.
It looks like there are two fets in the primary, have you checked them?

[ShortCircuited]

Re: Corsair GS800 Power Supply Problem

The VOLTAGE between pins 2 and 7 should be around 12 volts. what do you mean by OL? are you measuring the resistance between vcc & ground? Is that what your meter displays when the probes are shorted together?

Retest and resistance is 1.7kohm between vcc and gnd (2/7).

FPOB-Fault Protection is .38v to ground and 39 megaohms to ground.