Help identifying NTC value - Page 1
Forum section: electronics / repair

author: keenox
author_rank: Contributor
timestamp: November 14, 2024, 09:43:44 pm
content: Hi! I'm trying to repair a Corsair RM100x PSU with a blown NTC (along a blown cap and shorted MOSFET). The NTC has no markings on it. It is after the rectifiers, a coil and a diode.

author: fzabkar
author_rank: Super Contributor
timestamp: November 14, 2024, 10:36:09 pm
content: The diameter may give us a clue.

author: bte
author_rank: Regular Contributor
timestamp: November 15, 2024, 01:02:13 am
content: There's a review athttps://hwbusters.com/psus/corsair-rm1000x-atx-v3-1-psu-review/3/and the "parts analysis" section indicates the NTC is SCK-207R0 (https://www.alldatasheet.com/datasheet-pdf/view/1132411/THINKING/SCK207R0.html).

author: Harry_22
author_rank: Frequent Contributor
timestamp: November 15, 2024, 08:47:58 am
content: Hi!Carefully cut off the legs, gradually wipe off the soot trying to see the inscription. And finally, measure it with a tester.Estimate the power consumption of your device. Look at the rating of bulky capacitor. Most likely there is a PFC circuit.PSThere's probably a whole bunch of faulty parts there.

author: keenox
author_rank: Contributor
timestamp: November 15, 2024, 01:44:41 pm
content: @fzabkar:The diameter is a bit over 14mm@bte:Wow! Great find! Unfortunately mine is a different revision, as the layout is different. The big caps are the same, but mine has 3xIPA60R190P6 (one of which is shorted) and generally worse radiators for the mosfets (no fins). You reply was very helpful nonetheless!Harry_22:Did cut the legs, but didn't notice anything written on it. Today I looked again and managed to make out SKC 037. Coupled with bte's answer I managed to find the right one. Should I replace it with a beefier one?Indeed there are more components faulty. In the PFC circuit there is one MOSFET shorted, the film capacitor near the NTC was blown and the 2 bridge rectifiers seem blown (no conductivity). It's weird that the main fuse didn't blow.Looking in the datasheet provided bybteI can see that 037 is a bit underrated (820uF) for the 1150uF (680uF + 470uF) that this PSU has. Should I upgrade it to an SCK253R0 (1200uF capacitance, 14A max current)? (Just to add context, mine doesn't have a relay before the PFC, just this NTC)

author: Harry_22
author_rank: Frequent Contributor
timestamp: November 15, 2024, 07:20:52 pm
content: Check the thermistor resistance.Please take high-quality photos of both sides of the board.

author: keenox
author_rank: Contributor
timestamp: November 15, 2024, 08:08:39 pm
content: @Harry_22:It's blown. Measures at around 16k. How does that help you?I already wrote that I could discern the markings and identified the right NTC. I was asking if it's ok to replace it with a beefier one.

author: fzabkar
author_rank: Super Contributor
timestamp: November 15, 2024, 09:20:06 pm
content: Quote from: keenox on November 15, 2024, 01:44:41 pmShouldn't that be "SKC137"?

author: Harry_22
author_rank: Frequent Contributor
timestamp: November 15, 2024, 10:24:37 pm
content: Quote from: keenox on November 15, 2024, 08:08:39 pmSorry, I processed a lot of information today.But you still haven’t taken high-quality photographs of the PCB on both sides!PSI have 1kW professional PS with two MOSFET PFC keys. There are two SCK20160 in series. I remember the connection because the cutomer change the one to capacitor. But I don't remember regarding relay. Will check on monday.

author: keenox
author_rank: Contributor
timestamp: November 16, 2024, 03:48:21 pm
content: @fzabkar:I pieced the markings and the size together with the datasheet and the full model name (from the datasheet table) is SKC15037 (15mm, 3 ohms, 7 Amps)

author: keenox
author_rank: Contributor
timestamp: November 16, 2024, 04:03:17 pm
content: @Harry_22:Here you go. You still didn't tell me what you need them for.

author: Harry_22
author_rank: Frequent Contributor
timestamp: November 16, 2024, 05:07:20 pm
content: Quote from: keenox on November 16, 2024, 04:03:17 pmGreat photos!Thank you very much!You'll see soon...

author: Harry_22
author_rank: Frequent Contributor
timestamp: November 16, 2024, 06:28:35 pm
content: Here!By the way, everything became clear with your thermistor now. Usually it is not placed there - between MOSFET keys and HT Capacitor. It operates during startup when charging current flows through the Inrush Diode. But then it’s completely out of place.Use the one with minimal resistance - SKC15037 (15mm, 3 ohms, 7 Amps)Attached is a file for PaintNET. Look, thanks to your strong hand, how precise the layers are!Check the green components.https://drive.google.com/file/d/1FnUlIw8UpXSYTlo2fm6CLhklv_FOI4R_/view?usp=sharingPSSorry MOSFETs should be mirrored on the picture.

author: keenox
author_rank: Contributor
timestamp: November 17, 2024, 04:30:21 pm
content: I already did. The bridge rectifiers are ok (I think I didn't push the probes hard enough the first time). The inrush diode is ok. I didn't check the PFC module, but I also assume it's ok. The middle MOSFET from the PFC side (with the heatsink) is shorted and I think that was the main cause. It caused this thermistor and the film capacitor near it to blow.Now what I asked is if I can replace the original SKC15037 with the beefier SCK253R0 (3 ohms, 14 Amps)