Re: Zalman ZM500-GV stops after 40s and 5VSB drops to 2.5V
I replaced the CM6800 PWM/PFC chip, even though i sort of knew that it was probably OK
and i also replaced the 3.3V output caps (which tested good)
Same deal as before
It's not shutting down due to lack of load - when i connect a mobo and a hard drive, it shuts down a lot sooner
The FPO pin on the supervisor chip goes high when the PSU shuts down, but i'm not sure if it that's because it shutting down the PSU, or if it goes high when something else shuts it down.
Prior to this i bypassed the PFC section - and it makes no difference
The 3.3V rail starts close to 3.3V (2.29V sometimes) but quickly starts falling from the moment that it is powered up
I doubt that it is the standby chip that is causing that
Maybe the supervisor chip is faulty, but that wouldn't be causing the 3.3V rail to behave like that, unless it's somehow causing a lower and lower resistance path to ground via the 3.3V voltage/current sensing pins
But i don't see why that chip would be damaged
I think that that supervisor chip is dropping 2V across it's VCC to ground, when the PSU shuts down, which would explain why the 5VSB chip goes to 2.5V (yeah, i know that there's 0.5V missing somehere) - which is possibly normal behavior
VCC of the controller chip starts at 4.4V (from 5VSB), then goes to 11.1V (probably now supplied by the 12V rail), and then goes to 1.97V when the PSU shuts down
Something is stealing voltage from the 3.3V rail (maybe as some component heats up)
And it seems that that supervisor chip is shutting down the PSU, when it shouldn't be.
I wonder if they are separate issues, or if they are due to one fault only?
I replaced the CM6800 PWM/PFC chip, even though i sort of knew that it was probably OK
and i also replaced the 3.3V output caps (which tested good)
Same deal as before
It's not shutting down due to lack of load - when i connect a mobo and a hard drive, it shuts down a lot sooner
The FPO pin on the supervisor chip goes high when the PSU shuts down, but i'm not sure if it that's because it shutting down the PSU, or if it goes high when something else shuts it down.
Prior to this i bypassed the PFC section - and it makes no difference
The 3.3V rail starts close to 3.3V (2.29V sometimes) but quickly starts falling from the moment that it is powered up
I doubt that it is the standby chip that is causing that
Maybe the supervisor chip is faulty, but that wouldn't be causing the 3.3V rail to behave like that, unless it's somehow causing a lower and lower resistance path to ground via the 3.3V voltage/current sensing pins
But i don't see why that chip would be damaged
I think that that supervisor chip is dropping 2V across it's VCC to ground, when the PSU shuts down, which would explain why the 5VSB chip goes to 2.5V (yeah, i know that there's 0.5V missing somehere) - which is possibly normal behavior
VCC of the controller chip starts at 4.4V (from 5VSB), then goes to 11.1V (probably now supplied by the 12V rail), and then goes to 1.97V when the PSU shuts down
Something is stealing voltage from the 3.3V rail (maybe as some component heats up)
And it seems that that supervisor chip is shutting down the PSU, when it shouldn't be.
I wonder if they are separate issues, or if they are due to one fault only?
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