Hi, I have a Corsair CX400W that has been in use for a few years.
Recently I had to replace it because the owner complained that his PC would shut off for no apparent reason (It has a UPS too...)
To make a long story short the PSU is finally here at me now and disassembled.
There seems to be no problem to rectify the AC, I have a constant 330VDC on the main filter capacitor.
The 5vsb is generated by a Fairchild FSQ0165 which has just Q0165R printed on top of it.
If I plug it in I get a nice and stable 5v output, but after a couple of minutes with a small load it goes into a safety loop: shutting down the output and then trying to restart it.
It does this if I plug in a PC too, it runs for a minute or two and then shuts down, at which stage 5vsb pulses all lights on the mainboard as it tries to restart...
I replaced all electrolytic capacitors in the 5vsb section but it made no difference.
I also replaced diode D101 for a UF1007 even though it measured good, with no difference, I replaced it because the soldering on the back looked bad.
All the other diodes and zener diodes in the area measure good in circuit.
Between VCC and GND sits a 100uF 50v Suncon WX cap now, it was a 100uF 25v OST RLS before.
The voltage on this cap starts off at 16v but rises slowly to 18v at which stage the IC goes into it's safety loop.
The optocoupler has around 2 > 3v on the primary side depending on load.
On the secondary side was a 3300uF 10v OST RLX that I replaced with a 6.3v Rubycon MBZ
And finally a 16v 220uF OST RLS right on the 5vsb output cable that got replaced with a Rubycon ZLH 220uF 16v.
Once the chip is in the safety loop it's enough to remove the load for it to be able to stabilize the 5vsb again, but if I don't it seems to be stuck there forever.
I also noticed that if I'm probing the feedback signal on the optocpupler it seems to not enter the safety loop as quickly.
But if it "should have" then it's enough that I remove my probes from the feedback pins and it will enter the safety loop instantly.
It's worth noting that with no load I see around 720vdc between drain and ground, but with a load this goes down to a more sensible 600vdc.
Is not this too high, the datasheet says max 650v for the drain?
Any ideas what more I can check?
Recently I had to replace it because the owner complained that his PC would shut off for no apparent reason (It has a UPS too...)
To make a long story short the PSU is finally here at me now and disassembled.
There seems to be no problem to rectify the AC, I have a constant 330VDC on the main filter capacitor.
The 5vsb is generated by a Fairchild FSQ0165 which has just Q0165R printed on top of it.
If I plug it in I get a nice and stable 5v output, but after a couple of minutes with a small load it goes into a safety loop: shutting down the output and then trying to restart it.
It does this if I plug in a PC too, it runs for a minute or two and then shuts down, at which stage 5vsb pulses all lights on the mainboard as it tries to restart...
I replaced all electrolytic capacitors in the 5vsb section but it made no difference.
I also replaced diode D101 for a UF1007 even though it measured good, with no difference, I replaced it because the soldering on the back looked bad.
All the other diodes and zener diodes in the area measure good in circuit.
Between VCC and GND sits a 100uF 50v Suncon WX cap now, it was a 100uF 25v OST RLS before.
The voltage on this cap starts off at 16v but rises slowly to 18v at which stage the IC goes into it's safety loop.
The optocoupler has around 2 > 3v on the primary side depending on load.
On the secondary side was a 3300uF 10v OST RLX that I replaced with a 6.3v Rubycon MBZ
And finally a 16v 220uF OST RLS right on the 5vsb output cable that got replaced with a Rubycon ZLH 220uF 16v.
Once the chip is in the safety loop it's enough to remove the load for it to be able to stabilize the 5vsb again, but if I don't it seems to be stuck there forever.
I also noticed that if I'm probing the feedback signal on the optocpupler it seems to not enter the safety loop as quickly.
But if it "should have" then it's enough that I remove my probes from the feedback pins and it will enter the safety loop instantly.
It's worth noting that with no load I see around 720vdc between drain and ground, but with a load this goes down to a more sensible 600vdc.
Is not this too high, the datasheet says max 650v for the drain?
Any ideas what more I can check?
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