Replacing unknown NTC Thermistor in Corsair CX400

[goodpsusearch]

Re: Replacing unknown NTC Thermistor in Corsair CX400

Yes, they would.

Normal Ratings are B16 breakers wich allow only 3-5 times the nominal value.
Wich means that everything over 48A is crap and trips breaker (hello Sirfa!!)
And max is 80A.

However there is also the possibility to install a C16 breaker that allows 5-10 times the nominal value (=80-160A), but depending on the length of the cable it's not always possible.

And they are expensive as hell. At least double the price of a normal B16.
I've paid about tripple what a normal B16 breaker whould have cost....

That sounds like much but a B16 breaker cost as little as ~2€.
And I've paid ~9€ for one (Hager) C16...


First 1,5mm² copper wire is the norm here in Europe (German)
That is somewhat between AWG15 and AWG16...

Second: Normal breakers for that (as far as I know) is 16A with the B characteristics.
Although I've heard that 13A is the new norm and 16A is only allowed under certain conditions.

Third: In some regions like the old Communist Germany 10A are also used - with Aluminium wire. I can't say anything about that, never seen it, that's only what I've heard...

Actually it is more like:

10A for 1.5mm2
16A for 2.5mm2
20A for 4mm2
25A for 6mm2
32A for 10mm2

The problem is Corsair HX is almost the same thing as CX---M, just with bigger and more components. Design-wise, they look too similar and HX still has the same crappy flat heatsinks that the CX---M has. To me, that's a definite low-ball in quality. Even a Gold rated 700W PSU will dissipate over 70 Watts of heat. Divide that into three heatsinks, and you get 23W on average per heatsink - which is a bit too much for a fin-less heatsink.

You must love FSP power supplies

[Stefan Payne]

Re: Replacing unknown NTC Thermistor in Corsair CX400

Actually it is more like:
10A for 1.5mm2
16A for 2.5mm2
20A for 4mm2
25A for 6mm2
32A for 10mm2

Hm??
Where did you get those values?? For what country??
That (almost) looks like it is for Aluminium...

What I've found (for Germany) is something like that:
https://www.zaehlerschrank24.de/info...tstabelle.html

But that's just the most simple one, normally you have a table, depending on the laying method and the differences can be rather high...

[goodpsusearch]

Re: Replacing unknown NTC Thermistor in Corsair CX400

For 1.5mm2 cable its maximum current depends on many factors, but let's say it is ~ 15-19A.*

So, a 1.5mm2 line gets a circuit breaker with value of 10A, because as we know a 10A breaker opens in higher value of its nominal.

https://upload.wikimedia.org/wikiped...it_Breaker.svg

If we used a 16A breaker for 1.5mm2 line, protection of that line would be compromised, because we could pull 22A from it for example and the 16A breaker would never trigger!

*To know the max current with precision we would have to take into account the wire material (copper, aluminium), if it is multicore or singlecore cable, other cables that run near it etc.

[momaka]

Re: Replacing unknown NTC Thermistor in Corsair CX400

You must love FSP power supplies

Hehe, they're not all bad. Actually, I've seen some older FPS units that are very nice. Have pictures of two units that I need to upload here - probably the best built FPS of all time.

[Adrian_]

Re: Replacing unknown NTC Thermistor in Corsair CX400

I'm not sure how many of you are old enough to remember, but some 25-30 years ago all manufacturers of electric appliances were supposed to add the schematics of the whole thing to the manual sold with the device (be it a TV, a stereo or even a freezer and so on). This also included the part list, which made repairing a breeze once the defect was correctly identified.
I'm not sure when this habit (or were it laws/regulations?) ceased to operate but I'm amazed that at least in a highly regulated place like the EU the IT manufacturers are allowed to get away with selling stuff without even publishing the relevant schematics on their websites... [rant off]

[Agent24]

Re: Replacing unknown NTC Thermistor in Corsair CX400

PS: Please look for the protection chip.
Is it a HY-510N?? Seasonic seems to like this garbage protection IC...
Even in the 8pin world there are way better ones that support OCP on minor rails and/or UVP on +12V...

Yes. I can confirm mine uses the HY-510N also.

I can also confirm that the new NTC thermistor has also blown (don't know when that happened)

I'm starting to think there is something pretty strange going on with this PSU. I also noticed that the PC it was in, had been doing a DMI /ESCD data update on almost every POST. With a different PSU in, it's not doing that any more.

[Agent24]

Re: Replacing unknown NTC Thermistor in Corsair CX400

I think I spoke too soon. ESCD update still happens on this board even with a different PSU. Probably a BIOS bug instead maybe. The board only has F2 BIOS (Gigabyte) with nothing newer out yet.

But I still don't know why the new thermistor blew. What is the likely cause? Underrated component? Seems funny both blew quite hard though. Maybe there is a fault in the PFC circuitry?

[Agent24]

Re: Replacing unknown NTC Thermistor in Corsair CX400

I had a look at this again yesterday, after being annoyed by it and leaving it in a corner.

The design is such that the primary filter capacitor is initially charged via a diode direct from the bridge rectifier, and the NTC. The APFC circuitry is effectively in parallel with that diode, between the bridge and the NTC, and so there is no way a fault in the APFC could blow the NTC.

The only logical conclusions then are that for the NTC to blow, there must be either 1) a serious fault in the SMPS primary side, or 2) shorted mains filter capacitor. Since neither of these seem remotely true, I suspect that the NTC failed from old age.

This would fit with how my replacement NTC also blew, considering it was a used pull from a dead and much older PSU board.

I have now fitted a brand new EPCOS B57235S509M as the NTC. Time will tell what happens...

[PeteS in CA]

Re: Replacing unknown NTC Thermistor in Corsair CX400

Is there a relay or triac across this thermistor? In some PSUs the thermistor gets shorted out after some brief time interval. This allows use of a higher value of thermistor, to achieve a lower value of inrush, but whose hot resistance is so high that it would fry were it not shorted by the relay or triac. If there is such a relay or triac that failed, that might account for the frying of the thermistor.

[budm]

Re: Replacing unknown NTC Thermistor in Corsair CX400

If the APFC MOSFET shorted out it will blow the main fuse, or the NTC, and may take out the bridge rectifier with it also.

[R_J]

Re: Replacing unknown NTC Thermistor in Corsair CX400

I found this atx schematic and it uses a SCK-2R58 ntc, this is a 300watt supply

[momaka]

Re: Replacing unknown NTC Thermistor in Corsair CX400

Is there a relay or triac across this thermistor? In some PSUs the thermistor gets shorted out after some brief time interval. This allows use of a higher value of thermistor, to achieve a lower value of inrush, but whose hot resistance is so high that it would fry were it not shorted by the relay or triac. If there is such a relay or triac that failed, that might account for the frying of the thermistor.

I doubt you would find a circuit that "exotic" in a budget 400 Watt unit.

[Agent24]

Re: Replacing unknown NTC Thermistor in Corsair CX400

Indeed, there is certainly no relay and I've not seen a Triac in there either.