Problem with PSU Cooler Master MPX-5501-AMAAB

[stomanata]

Happy new year.
This PSU use WT7527V supervisor.
On purple cable i have 5V, but on #4 of WT7527V i have 0.21V.
If i try to start PSU with short between green and black it star for a second and stop.
For what other to check? I now that is needed more info but i don`t know what else to share

[CapLeaker]

Means the supervisor is likely shutting it down. Look at the FPOB pin. If it is high, the supervisor didn't like something. If you ground out the FPOB pin, you disable the protection and the PSU starts regardless. Be careful and do some checks before you defeat the protection.
Also means the primary switching side is good, as it was able to start.
What you have to check is the primary main filter capacitor and the secondary power rails for shorts, bad output caps, etc. before defeating the protection.
Post some high resolution, straight shot pictures from the top and back side of this PSU.

Could be a bad main filter capacitor in the primary, a short on one of the DC rails on the secondary, maybe a missing or not correct voltage, a bad supervisor chip, etc.

[harp]

What is the brief history of psu, is from your working computer or else?

Simptoms you mentioned remind me to one atx psu, see simptoms from 14 min to end

https://www.youtube.com/watch?v=d7jXHcYf9wk

Some psu need a proper load like connection to motherboard in order to PG (power good grey wire) bring high, it is not a fault.

So check for that also is everithing else is ok.

[temyth]

Happy new year.
This PSU use WT7527V supervisor.
On purple cable i have 5V, but on #4 of WT7527V i have 0.21V.
If i try to start PSU with short between green and black it star for a second and stop.
For what other to check? I now that is needed more info but i don`t know what else to share

try injecting 12v, 5v and 3.3v with a regulated psu into the respective voltage lines of your PSU to see if there is any short.
besides, take a look at the primary section of the PSU and check for zeners or resistors with some fault.
you know how the power supply ended up not starting? the history of how the problem happenned the first time would be good.

[stomanata]

I work after test lamp (75W)
In normal state on FPOB there is 4.91V. When i connect green to black - it goes to 0V. I make bridge between pin #2 and #3 (FPOB and GND) and then green to black - again
PSU start for second and power off.

I take second working PSU and with 5W, 12V bulb i injecti 3.3, 5 and 12V. When i power up working PSU - it is OK. There is no short in not working psu.
When i try to power up not working PSU lamp light up may be at 100%.
4 diodes on heatsink (for low voltages) are OK - i remove them with heatsink and measure them.
I change 1 capacitor 16V, 2200uf because it has a little bit bad readings - marked with red line.
On video... may be he check for short circuit on every line...

[temyth]

I work after test lamp (75W)
In normal state on FPOB there is 4.91V. When i connect green to black - it goes to 0V. I make bridge between pin #2 and #3 (FPOB and GND) and then green to black - again
PSU start for second and power off.

I take second working PSU and with 5W, 12V bulb i injecti 3.3, 5 and 12V. When i power up working PSU - it is OK. There is no short in not working psu.
When i try to power up not working PSU lamp light up may be at 100%.
4 diodes on heatsink (for low voltages) are OK - i remove them with heatsink and measure them.
I change 1 capacitor 16V, 2200uf because it has a little bit bad readings - marked with red line.
On video... may be he check for short circuit on every line...

hmmm i see...try to get all the primary mosfets out (PFC and main switching) and test them to see if they're working. you can do it with a multimeter to see if they're switching or with a component tester. since a 75w lamp is going bright when you try to start it we may have a short or damaged mosfet that is not letting the PSU start. take a little bit more of attention in the PFC mosfets, they are damaged pretty often.
if the 75w lamp is getting pretty bright it indicates that the power consume of primary is pretty high, which can indicate a short in the secondary (which you already tested and we dont have it) or a short or damaged component in the primary. try also checking for shorted resistors or zeners that associate with the mosfets in the primary, they also get damaged quite often

[CapLeaker]

If you read the WT7527V datasheet, it got 2 fault protection circuits. FPOB and PGO. That's it. you have to check what them 2 pins are doing and why they shutting down the PSU.

[stomanata]

I remove all mosfets with heatsin and test all them with universal tester (for transistor, capacitor, resistor etc...) and all of them are working.
Next i`ll unplug all optrones and test them. There is 1 resistor R500 and on PCB i measure over it 2.5ohm. I`m not shure in his code but it
looks like red red gold gold green. But nowhere there is option gold to be on 2nd or 3rd position... Even if colours are red red yellow yellow green - it
must be some kiloohms.
Also will try to check where are going FPOB and PGO pins.
Btw on primary side there is cm6800tx IC. I`ll check also what it has on its pins.

[temyth]

I remove all mosfets with heatsin and test all them with universal tester (for transistor, capacitor, resistor etc...) and all of them are working.
Next i`ll unplug all optrones and test them. There is 1 resistor R500 and on PCB i measure over it 2.5ohm. I`m not shure in his code but it
looks like red red gold gold green. But nowhere there is option gold to be on 2nd or 3rd position... Even if colours are red red yellow yellow green - it
must be some kiloohms.
Also will try to check where are going FPOB and PGO pins.
Btw on primary side there is cm6800tx IC. I`ll check also what it has on its pins.

is pretty common to find these kind of resistors of low resistance in the primary of a PSU, they are fusistors, they act as a fuse. Try powering the PSU with 110V AC to see if the PFC system works to pull the voltage to +300VDC. If the PFC IC generator isn't working you're going to see something about 170VDC.
I still not understanding why the lamp is going bright if everything seems to be right...that's strange. check if everything is right in the soldering layer, maybe some line is shorted with something, it already happened to me one time.

[CapLeaker]

Could be a bad cm6800 as well… clue is if your PFC is working or not. A bad main filter capacitor does strange things too. Don't worry about a low reading resistor. I'd be worried for a low ohm reading resistor is reading high ohms. Keep poking around!