coolermaster v650 atx repair - Page 1
Forum section: electronics / repair

author: ants2
author_rank: Newbie
timestamp: August 13, 2025, 05:04:30 am
content: Hi guys, i picked up a broken powersupply free, thought I would see if anything obvious was burnt/exploded. I only have experience on simple valve/tube amplifiers, so know how to work safely with HV.. But this is above my skill set obviously.the 5vsb works. When you jump the green wire to gnd, the voltages on the 12v outputseems to jump to the correct voltage then it turns itself off instantly , also the 3.3v jumps to 3.3v then slowy drops, however the 5v only goes to 0.3v..I measured resistance on the outputs they rise like a capacitor charging no short.. I measured the diodes and transistors couldnt see any shorts. WHen you turn it on via atx plug the primary filter cap voltage increases - indicating active pfc is working i believe ?https://www.techpowerup.com/review/cooler-master-v550s/4.htmlhere is some pictures of the inside

author: Psi
author_rank: Super Contributor
timestamp: August 13, 2025, 05:17:04 am
content: Could be a lot of things.How long is there from shorting green to ground and it turning off.Is it practically instant, or 500ms to 1000ms?Check if every single output voltage is normal, including negative ones. If one is not coming up in time that can trigger a shutdown.If every voltage is coming up normally and their voltages get to where they should be but after 500-1000ms it turns off I would suspect a fault related to current sense and/or overload protection. There is some lag before shutdown because graphics cards can draw really large busts of peak current, so it has to allow the high current situation for long enough to conclude it's actually a fault before powering off. Otherwise it might turn of in the middle of your game.Could also be that the voltage is not within the correct < > window to be considered 'good' within a set time. eg 12V rail only getting to 10V would probably do it. That sort of thing.If it turns of pretty much instantly, like the fan twitches a bit, and voltages only start to rise but never get to full voltage then its probably a short on one of the rails somewhere. But could also be a fault where it only thinks there's a short

author: amyk
author_rank: Super Contributor
timestamp: August 13, 2025, 05:19:04 am
content: Likely to be protection circuit sensing an abnormal condition and shutting down.From your link it says it uses aPS223monitoring IC, so use that datasheet to check whether it's triggering the shutdown.

author: fzabkar
author_rank: Super Contributor
timestamp: August 13, 2025, 05:32:39 am
content: Some working PSUs will shut down in the absence of a load.

author: ants2
author_rank: Newbie
timestamp: August 13, 2025, 05:42:27 am
content: thanks i will look into that.. I added some extra info - the 3.3 line jumps to 3.3v then slowly drops , the 12v goes to ~12v and slowly drop back down.. however the 5v line only goes to 0.3v.. the psu switches off almost straight away

author: Psi
author_rank: Super Contributor
timestamp: August 13, 2025, 06:32:13 am
content: Quote from: ants2 on August 13, 2025, 05:42:27 amSounds like you know where to look then.Check for blown fets related to 5V. If they're all good it might be worth checking the feedback opto on the 5V rail. Probably have to remove it to check. I would say check diodes on 5V rail but they're probably using fets given the current involved.You could try inject a low voltage (less than a volt) into the 5V rail with a current limit to see what gets warm.But injecting voltage can be a bit risky. Best to look for a short before trying that, and it can be hard to locate a hot spot without a thermal cam.Could also be something else that happens before the 5V rail starts, but sounds more like 5V issue to me.

author: ants2
author_rank: Newbie
timestamp: August 15, 2025, 03:26:15 am
content: it has 2 boards standing up one for each 5v and 3.3." Each of the two VRMs also has an APW7073 PWM controller and a single CSD86350Q5D fet."https://www.techpowerup.com/review/cooler-master-vsm750/images/in_secondary_caps2.jpgI measured both boards receive ~10-12v in from my dmm, does that mean the fault is localized to that board ?Anyway I can find out which component is bad ? like how does the power flow through these 3 semi conductors , which is first in the line.There is also a third semiconductor thing which the techpowerup doesnt mention, which I cant read - a cap in the way.. would it be an identical mosfet? The part numbers look somewhat similarI suppose I could swap components from each board as techpowerup says they are the same , except for the third thing circled

author: ants2
author_rank: Newbie
timestamp: August 15, 2025, 03:42:19 am
content: "You could try inject a low voltage (less than a volt) into the 5V rail with a current limit to see what gets warm.But injecting voltage can be a bit risky. Best to look for a short before trying that, and it can be hard to locate a hot spot without a thermal cam."I will try remove the board and measure the mosfet(s)I can remove the board and add 1.5v from an aa battery to the output?

author: Kean
author_rank: Unknown
timestamp: August 15, 2025, 04:44:08 am
content: Quote from: ants2 on August 15, 2025, 03:26:15 amLook at the datasheet for the APW7073 and it shows you the typical application circuit which uses two MOSFETs, an inductor, and a handful of capacitors and resistors.https://www.techpowerup.com/review/andyson-titanium-n700/images/APW7073.pdfThe values of some components will differ between the 5V and 3.3V boards - possibly just one resistor, but maybe also also different inductor and capacitors.If you remove the modules, you can power them off a 12V supply (10.8-13.2V recommended). Use either current limited supply, or with a fuse of maybe 2A for initial tests.I don't think using a 1.5V battery at the output will be much help, but maybe it will identify if a FET is shorted.

author: Psi
author_rank: Super Contributor
timestamp: August 15, 2025, 11:21:26 am
content: Quote from: ants2 on August 15, 2025, 03:42:19 amNo you need a current limited supply for safety when injecting voltage.

author: ants2
author_rank: Newbie
timestamp: August 16, 2025, 03:25:28 pm
content: I had trouble removing the board from the main pcb its held on by 5 solid lugs and only 1 30w soldering iron, ended up putting it on top of a toaster and pulling it out..carnage insuedhttps://imgur.com/a/8OgFf2vhttps://imgur.com/a/vzx02kLthanks kean for the great link.I dont know what value caps they are, do you think I should use the typical circuit ? 1uf and 0.1uf should be the ones..The resistance readings i measured in circuit on the mosfets are similar both on the working 3.3 v and the 5v damaged one. No direct shorts Do i need to unsolder them to test.Im assuming the apw chip is the issue, triggering low voltage shutdown , I need a new one regardless

author: Kean
author_rank: Unknown
timestamp: August 17, 2025, 12:35:07 am
content: Quote from: ants2 on August 16, 2025, 03:25:28 pmThankfully not too hard to fix that damage, and these buck converter modules are quite handy separate from the ATX PSU.Quote from: ants2 on August 16, 2025, 03:25:28 pmYes, the 1uF an 0.1uF values should be fine - these are the caps for Vcc and Boost which are not too critical anyway. I would suggest 25V or 50V parts.Quote from: ants2 on August 16, 2025, 03:25:28 pmOK, if no direct shorts on the MOSFETs when measured in circuit, then they are probably OK. If you can get the APW chip cheaply, then certainly worth trying to swap it. Not much to lose.

author: xenoxaos
author_rank: Contributor
timestamp: August 17, 2025, 01:05:44 am
content: Yeah... definitely sounds like the 5v rail is shorting somewhere. If it has the modular rail boards that give the 5 and 3.3 volts from the main 12v. Pull the module out. If you can't unsolder it you may be able to snip the legs and be able to replace them with pin headers later. My guess would be a faulty capacitor on the output that gave out and turned itself into a resistor that potentially can make confetti.

author: ants2
author_rank: Newbie
timestamp: August 18, 2025, 12:48:32 pm
content: I ordered the parts, while im waiting Im trying to find the optocoupler (s) , could be more than one ?on the top side of the board there is one PS2561D-1.., cant seem to get it to measure properly in circuit like youtube guides saybottom side: some 4pin chips not sure what they arecant read the part number on the 2 grouped together but I can see the first one however it doesn't show up on the internet.

author: Kean
author_rank: Unknown
timestamp: August 18, 2025, 01:09:25 pm
content: Those 4-pin devices are likely Liteon LTV-357T Photocouplers (aka optocoupler or optoisolator)Datasheet shows marking info- first line as "L" (brand) + 3 digit date code (YWW) - "G" for year will be in a cross reference table somewhere- second line as 357T - yep!- third line as factory code, rank, and VDE - so XB is China-TJ factory, and B ranking. Ranking relates to CTR range (current transfer ratio). VDE is safety conformance, which isn't marked so doesn't apply.https://optoelectronics.liteon.com/upload/download/DS70-2001-012/LTV-357T%20series%20201606.pdf

author: MathWizard
author_rank: Super Contributor
timestamp: August 18, 2025, 08:43:15 pm
content: Most of the computer PSU's I've worked on, were from before 2012. It looks like they are going at lot more to SMD, which makes sense I guess since it seems SMD stuff is usually cheaper than through hole patrs.

author: ants2
author_rank: Newbie
timestamp: August 20, 2025, 10:15:32 am
content: Curiosity got the better of me and i tried connecting live 5vsb to 5v output with a 47k resistor in series, with the 5v board removed .. Had some sparks.. Now I dont seem to get any voltages except 5vsb.. No relay click sound when trying to start it with the ps_on wire. Did i break something..Perhaps knocked off smd components with my board removal, looks like some diodes may be missing..https://imgur.com/a/0n88zyQthese ones seem to be gone, chip on left is ps223, one missing diode runs to the vcc of the ps223 perhaps no power herehttps://imgur.com/a/Cd6gRXVand a big one here. seems to run to the fan and the thermistor temp control thingshttps://imgur.com/a/fny97MTand my board with missing circled..