Corsair CX650M AKA Vengeance, help identifying zener diode value

[PCTechnics]

Hi guys im trying to fix a Corsair CX650M,same like the Vengeance (I didnt saw any more change than the sticker) the zener diode is under PCB marked ZD4A anyone know the value?
Thanks!

[Stefan Payne]

Re: Corsair CX650M AKA Vengeance, help identifying zener diode value

None?
Because it doesn't look like there was ever one there...
Another possibility would be to look at the datasheet of the Chip it's used for...

And the real problem seems to be above that...
Broken (SMD) Resistors, broken Traces of the PCB...

[stj]

Re: Corsair CX650M AKA Vengeance, help identifying zener diode value

there was one once - the laq is missing indicating a glue-spot.

[PCTechnics]

Re: Corsair CX650M AKA Vengeance, help identifying zener diode value

Stefan, i just cleaned and changed 6 resistors, 1 mosfet CEF04N7G , 1 ceramic cap, 1 fast recovery diode (FR157) and reconstructed the PCB trace.I just need to know the voltage of that Zener diode. Messy solder job but all was replaced in this picture. Check this to see what was like when i opened it https://www.badcaps.net/forum/showpo...postcount=1318 Regards!

[PCTechnics]

Re: Corsair CX650M AKA Vengeance, help identifying zener diode value

Someone with contacts @ Corsair to help me?

[momaka]

Re: Corsair CX650M AKA Vengeance, help identifying zener diode value

Can you post a better picture of that area where the missing Zener diode is? Also, can you post the part number of U8?

From what I can trace so far, ZD4A appears to be connected to the Cathode of D11, which has its Anode connected to the Cathode of D12. So to me, this looks like ZD4A may be part of a circuit that regulates power to Vcc/Vdd of U8. If this is the case, then we just need to know what is the maximum voltage that U8 takes for Vcc/Vdd, and chose a Zener diode accordingly, so that the regulated voltage does not exceed that.

FWIW, I had to do that once on a TV power supply that blasted its Zener diode to pieces. So if we know what U8 is and with some better pictures, we should be able to figure this out.

[redwire]

Re: Corsair CX650M AKA Vengeance, help identifying zener diode value

Long PCB trace run ZD4A appears to connect to Q12 (SOT-223; collector?-) then HV opto U3. Not sure what this subcircuit is about.

I don't see a path to U8. In CX650M teardown, U8 is OB5269 +5VSB PWM controller which typically does not use any zeners. It has a built-in 32V zener on VDD pin 6, and HV pin 8 is ok to 500VDC) R36 has HV across it, should be no flux and good soldering)

[momaka]

Re: Corsair CX650M AKA Vengeance, help identifying zener diode value

Your right, redwire. I traced the circuit again based on the improved contrast version you posted (don't know why I didn't think of doing that), and ZD4A indeed does not appear to be associated with U8.

That said, some of what I said about the way it is connected still stands. Mainly, it appears that D12 is the first rectifier of the 5VSB's primary-side auxiliary winding. It likely provides power to all ICs on the primary side, including U8. After the rectification from D12, looks like the primary-side auxiliary winding rail takes two paths: one through D23 (which does appear to be associated with U8), and another through D11, after which it goes through that zero-Ohm resistor and then gets regulated by ZD4A. So that second path there probably provides power to the primary-side PWM/PFC controller, and ZD4A likely is used to limit the voltage going to that controller.

So what to use in place of Zener diode ZD4A? I say check what the PWM and PFC controllers are and post the part numbers here.

[PCTechnics]

Re: Corsair CX650M AKA Vengeance, help identifying zener diode value

Sorry for delayed answer momoka and thank you guys! Detailed component description from Tom's Hardware review http://www.tomshardware.com/reviews/...su,4770-3.html

[momaka]

Re: Corsair CX650M AKA Vengeance, help identifying zener diode value

Thanks.

So looks like PWM and PFC are handled by the same controller - the venerable CM6800TX. According to its datasheet, it can take up to 18 Volts max on its Vcc pin.

As for the circuit... looks like I was on the right track. After the second diode, D11, the primary-side aux. rail gets filtered by that 100 uF, 25 V cap you marked on your diagram above. Since I don't see any resistors before ZD4A, it most likely is used for over-voltage protection of the primary-side aux. rail rather than regulation. The voltage then goes to Collector/Drain of Q12 (I have not looked up what it is, but we don't really need to know at this point). The optocoupler to the left of U10 (U3?) is likely used for enabling power (Vcc) to the CM6800TX chip. You can see that the primary-side aux. rail also connects to one of the legs on that optocoupler, and the leg adjacent to that is connected to resistor R66 ("512" or 5.1 KOhm) and into the Base/Gate of Q12. So when the secondary side is signaled by the PC to turn ON, it allows current to flow through that optocoupler, which in turn allows power to go through Q12 and likely power the CM6800TX chip.

So with all of that said... I think an 18V Zener might just work in place of ZD4A. But before installing that, plug in the PSU to your wall outlet (but do NOT plug to a PC and do NOT try to turn it on) and measure the voltage you get between primary-side ground and the primary-side aux. rail. The easiest spot to do what would be to measure the voltage across that 100 uF, 25 V cap. Then post what voltage you get. Also put a small load on the 5VSB line - around 500 mA - and then measure that voltage again. Then try the same with a 1 Amp load.

The reason to do this is to see how high the voltage on the primary-side aux. rail can go without the Zener diode so that we can hopefully get an idea of what to use.

If the voltage is much lower than 18V (say, 10-12V max), I suggest using a slightly lower Zener voltage - the next lower value below 18V (I forgot what that is... 16.3V? or 15V?)