BeQuiet! Pure Power 9 CM 700W +5VSB only

[Nabri]

Hello everyone,

I’ve been trying my best to repair a power supply I have recently bought, but I’ve had no luck with it as I can’t find any schematics or board views online for this specific model.
The current issues are as follows:
if I short the PS_ON pin to ground, a relay will click and the fan will spin for 0.1 seconds, and then nothing else.
I could not find any blown components or IC’s inside, but measuring all the output pins has led me to a conclusion of sorts, I only have +5VSB and all the other power rails show a very small voltage, like, 0.30V, for example.
This is my first time attempting to repair a power supply, I have more experience with GPU’s so I’m stumped as to where I’m supposed to be looking and measuring, any help is appreciated!

[CapLeaker]

First thing: Welcome to Badcaps!

A picture can say 1000 words. Use the attachment function an upload straight shot, high resolution images from top and bottom of the PSU. This will tell a story on how this thing is built.
From what I gather so far, it sounds like the supervisor IC is shutting everything down. This can be for various reasons. Look at the supervisor IC somewhere in the secondary and see what the part number is (something like WT75xx). I think it is a WT7527.
Once you got that, pull the spec sheet and go over the pin out. Find the FPOB pin (3) (fault protection output pin) and measure the voltage on it. If this pin is "high" (something like 5V) the supervisor has shut the PSU down and there is some kind of a problem with either one voltage rail on the secondary or all of them. If you want a good read on how to fix a head scratcher, here is an example of mine: https://www.badcaps.net/forum/troubl...300bn7-2-blown
Do not get too exited poking around in the primary while being plugged into power mains. The power factor correction, boosts the voltage up to 400VDC on the main filter capacitor! Be warned.
If you measure DC voltages after the bridge rectifier on the primary side of the PSU, your ground point is always the negative terminal on the main filter capacitor.
Measuring voltages on the secondary (low voltage side) you ground point here is you main ground on this side. Good luck!

[Nabri]

Thank you for the warm welcome!

after probing around I found something interesting, the third pin of the IC does indeed measure 5V, I read the thread you linked and I decided to try to short the pin to ground and the relay will click rhythmically, about every 0.5 seconds, which is interesting.
I did also find that a rail seems to be completely missing, starting from a blue through hole resistor and down to a SMD diode on the back of the PCB near the 240V input, the solder joint looks iffy but that was me previously. If I use my multimeter, I don’t even get a reading, it just remains on 1 in continuity mode.

[Nabri]

After further testing and another look at the post you linked, I’ve come to the conclusion that the main Teapo 420V 390uf capacitor is completely effed.
I measured the voltage after turning the power supply on and I got -110V on the high voltage side and after disconnecting it without discharging the cap, it reads… 0V. I’m pretty sure it’s dried up inside as it looks like new outside (besides a teeny tiny bit of bulge on top, but no leaking)
I’m not very sure though, I’ll order a new one and test it out and see what happens.

[Nabri]

Confirmed!
Just desoldered it and got to testing, completely open circuit, even tested a known good capacitor out of circuit just to see if I wasn’t crazy and yep, this one is totally dead.
So that makes two of us who’ve had issues with Teapo caps, I’ll be adding them to my list of brands to avoid. (I’m pretty sure their lower maximum rated temperature is what causes them to dry out, since power supplies get pretty warm and most people who own a computer always forget to clean out the insides of them, so they get clogged with dust and lint, causing them to run hotter)

[CapLeaker]

Good job! See… power supplies aren't that bad, once you know how to go about fixing it. The snap in caps seems to be a problem. Not saying this is always the case, with the main filter capacitor being bad (I had seen them go totally short too, but that's a rare case), but it can happen and the supervisor doesn't like it and turns the PSU off.

[Nabri]

I have already ordered a replacement and will update once it is soldered in place.
I hope the problem was this cap, I’ve read online that capacitors measuring open circuit are completely normal, but I’m not sure. I tested a known good smaller cap in continuity mode and saw a value rising until infinity, which is exactly what the bad cap doesn’t do…