Corsair GS800 Power Supply Problem

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Re: Corsair GS800 Power Supply Problem

Sleep helps.

Power supply tester is applying a 329mah load to 5v+ rail. 15 ohm resistance I have been chasing is in the power supply tester itself. UGH again! Without PSU tester in place and 12v applied to daughter card w/bench power supply current is 137mah. This sound right?

Applied 12v to daughter board with a thermocouple attached. U1 temp rose from 77f to 96f and settled there in about in about one minute-draw at 307mah. Removed PSU tested and current dropped to 136mah but temp stayed at 99-100f.

Current state in this Corsair PSU SAGA is 5v stdb that does not power on. That is serious progress from where this thing started.

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Re: Corsair GS800 Power Supply Problem

Supplied corresponding power to each rail (secondary side; 3.3, 5 and 12) to see current draw-PSU tester not connected:
1. 12v - 137mah
2. 5v - 61mah
3. 3.3v - 1mah

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Re: Corsair GS800 Power Supply Problem

Connected oscilloscope (TDS 320) to 12v and there is no response. Did same for 5v and 3.3...no signal.

Primary side detecting a problem and not trying to startup secondary side optocouplers maybe? Could the Q12 short have caused other damage along the same circuit maybe? It seems Q12 is controlled by pin 5 of the CN1 riser board. Has 160vdc to positive terminals of Q12, but negative terminal is no being grounded by the CM6800 riser card as it was shorted before and constant on state. Reference. post 82.

- U10 oc controls appears to control 5vstdby
- U3 and U5 maybe signal for large transformer.

U3 and U5 trace back the the vertical riser board (CN1) on primary side. Controller IC on this riser is a CM6800TX.

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Re: Corsair GS800 Power Supply Problem

Removed riser board on primary side again to get to the PFC controller (CM6800tx).

Traced the riser board to Vcc of this PFC controller (in-circuit) and applied 15vdc (typical) to the riser board which results in 10.1vdc to pin13 of the cm6800. Reasonable voltage drop? datasheet states min. is 10vdc.

Pin 14 is Vref and should be 7.5vdc. It does go to 7.5dc but is extremely unstable, drops out completely then jumps back to 7.5vdc.

Pin 15 Vfb Is typical 2.5vdc and is actually .0663.

All of the above testing is in-circuit.

I put a new CM6800TX in breadboard applying 15vdc to vcc. Vref gives a stable 7.669vdc and Vfb provides a stable 2.18vdc.

Question: original controller faulty or just normal in-circuit? Interesting...that Q12 PNP that RJ found was shorted causing PSU to be in constant-on state traces to VCC on riser board. Is it likely that Q12 being shorted damaged PFC controller (CM6800TX)?

Thanks for any help.

Top Photo: Third pin from top is ground 6 is Vcc for controller.

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Re: Corsair GS800 Power Supply Problem

Tagged some jumper wires directly to the original controller while still in-circuit and got a stable 7.5vdc for Vref and a stable 1.766vdc for Vfb. Consuming 21mah. Maybe surrounding SMDs causing the erratic readings?


New-out-of-circuit consumes 0mah during testing.

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Re: Corsair GS800 Power Supply Problem

Decided to chase the voltage. Applied 15v to riser board. Maybe one of these two caps that are in parallel? Update:First two caps where the voltage drop begins are fine.... Gotta be getting close. Any ideas?

D4 testing odd in circuit. D2 testing fine. D4 look bad to anyone-goes to PFC driver output on cm6800 controller? Hard for me to tell when in parallel with other components. if D4 I don't understand why a drop at the two capos where the 3.7v drop begins. Why not after the diode? Or maybe it is one of the two caps where the drop is first noted? I don't have an EST just doing a simple capacitance test with DMM.

* voltage unstable bouncing from 3.7-4.2v

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Re: Corsair GS800 Power Supply Problem

".237 nF" seem correct for this capacitor (C15)? When removed the voltage is WAY more stable around 4.2v.