PSU repair - Page 1
Forum section: electronics / repair

author: hpapagaj
author_rank: Contributor
timestamp: January 24, 2019, 10:05:39 pm
content: I ordered a PSU from china, it worked for 12 hours only.What I found is a blown fuse and 2 bad diodes. If am not wrong 2 shorted diodes can cause the fuse to blown up? For what reason can a diode fail in a new PSU? Other components seem to be OK.

author: fzabkar
author_rank: Super Contributor
timestamp: January 24, 2019, 10:24:50 pm
content: Is the clamping bracket across the MOSFETs (?) touching the wire link on the PCB?

author: mariush
author_rank: Super Contributor
timestamp: January 24, 2019, 10:28:54 pm
content: Yeah, the metal bracket that holds the mosfets or diodes to case should not touch that wire link on the circuit board.And it looks to me like both are fully isolated in plastic case, so you may want to drill a hole for each part and screw them through the hole, after adding a bit of thermal paste for better heat transfer.

author: hpapagaj
author_rank: Contributor
timestamp: January 24, 2019, 10:32:49 pm
content: What a good catch, I didn't notice that. I am not sure in the answer, because I already dissasembled it, but here are the original images before dissasembling:https://imgur.com/a/M9LFkQ7From what I see on the picture, I would say yes, it is touching that wire link on the PCB.Can this the cause of the failure?

author: hpapagaj
author_rank: Contributor
timestamp: January 24, 2019, 10:34:34 pm
content: "And it looks to me like both are fully isolated in plastic case, so you may want to drill a hole for each part and screw them through the hole, after adding a bit of thermal paste for better heat transfer."Thanks for the recommendation, I will follow your instruction. There was no thermal paste at all.

author: Armadillo
author_rank: Super Contributor
timestamp: January 24, 2019, 10:55:35 pm
content: It happened to me within the instant I power it up.It's obviously an irresponsible clone. I lodged a complaint to the Chinese authority for imitation clone endangering lives. The supplier was banned, never see him again.Yes, the problem is almost the same, the slanting heat sink touches onto the diode and the whole thing exploded.You should demand a refund before you open it up.Too bad, too many of them.

author: fzabkar
author_rank: Super Contributor
timestamp: January 24, 2019, 11:01:36 pm
content: I found a pop rivet (?) rattling around in one Chinese made PSU. I didn't turn it on.

author: Armadillo
author_rank: Super Contributor
timestamp: January 25, 2019, 06:11:48 am
content: Just look at the disaster causing whole house in darkness, power tripped.It's not imitation, its a fake!.Just look at the fake fuse."simon" fuse? hahahahahahaI lodge a compliant anytime to the authority.

author: Wolfgang
author_rank: Super Contributor
timestamp: January 25, 2019, 12:18:00 pm
content: There should be a law forbidding that ICs leave their homestead on the PCB without a written consent from their owner.

author: montarbo
author_rank: Contributor
timestamp: January 25, 2019, 06:19:20 pm
content: Cheaping on basic stuff is never good.

author: Wolfgang
author_rank: Super Contributor
timestamp: January 25, 2019, 06:24:23 pm
content: Thats a new world record in design flaws per cubic centimeter. People designing this should be tarred and feathered.

author: Armadillo
author_rank: Super Contributor
timestamp: January 25, 2019, 07:07:49 pm
content: Have you guys ever "SEEN" the "METAL LEAD" protect the fuse and not the other way around.?World Record in Cheaping and Fakes.Don't know what happen to their Customer Protection & Product Safety Compliance Authorities there, how did they let this thing pass?My word of advise is;First you compare the weight of the SMPS, if is too light, don't buy, if you can't find the weight information, don't buy.Even though you can see all the compliance logos printing coupled with the price being set not ridiculously cheap, may likely fool buyers.Save alot of trouble and blackout or RF interference.

author: janoc
author_rank: Super Contributor
timestamp: January 25, 2019, 11:43:34 pm
content: Quote from: Armadillo on January 25, 2019, 07:07:49 pmEven simpler - don't buy power supplies from random vendors in China but from reputable sources and brands. Cheaping out on stuff that could kill someone or set your house on fire is an incredibly stupid idea. Decent supplies are not that expensive.

author: Armadillo
author_rank: Super Contributor
timestamp: January 26, 2019, 12:48:22 am
content: Well the smart elusive Chinese Sellers quickly caught up with simple minded thinking by Not selling the price cheap, fake themselves with Super Stars rating, that of reputable sources.Better Still, don't cheap yourself at all by NOT buying from China, buy from Element14, Amazon or the likes for added assurance.But, the real point is, if you are going to buy something that you are not familiar with, One off kind....you are going to face with many new fresh unknowns in the market.Easy to say, not easy in reality especially for new fresh buyers.We can only practically advise how to differentiate it.Oh, BTW, do you know the reputable source/s in China for replacement power supply adapter for Yamakasi Leonidas 30" LCD monitor.Quote from: janoc on January 25, 2019, 11:43:34 pm

author: wasyoungonce
author_rank: Frequent Contributor
timestamp: January 26, 2019, 01:00:04 am
content: Quote from: fzabkar on January 24, 2019, 11:01:36 pmmeh found an extra screw in an F18 FLIR LASER PSU.These were brand new passed QA etc. They just arrived from USA years late as they had design issues of flash over at altitude. Finally they were done eagerly accepted at our workshop. My shake test QA found it. The factory Rep was furious his factory effed it up but appreciative. It was just something I did to all boxes I had to pass.We had to open and inspect them all after that. hahaha QA ISO and NASA stds yeah right.In general some Chinese stuff is ok but particularly PSUs get knocked off then the knockoffs get knocked off so the knowledge why things were done a particular way is lost.Sent from my iPhone

author: janoc
author_rank: Super Contributor
timestamp: January 26, 2019, 01:38:13 pm
content: Quote from: Armadillo on January 26, 2019, 12:48:22 amWell, that's what I meant. Buying a power supply from AliExpress/eBay or Alibaba is buying a cat in the bag unless you have the vendor thoroughly vetted already.Quote from: Armadillo on January 26, 2019, 12:48:22 amThen don't be an idiot and buy that component from a local supplier, such as Mouser, Farnell or similar. You may not get a better component than the Chinese one and you will likely pay more but at least you will have a neck to strangle should anything go wrong with it. That alone is worth the extra money.Another aspect of it is that if you buy and import a supply that isn't compliant with your local norms and doesn't have (or they are fake) the necessary certificates (CE, UL, etc. - therefore the device was not intended for your market) and it burns your house down, you may not get a dime from your insurance if they catch the wind of it. That alone is a good argument to buy stuff like this locally where someone who hopefully has an idea what they are doing has weeded out the worst abominations from you.Quote from: Armadillo on January 26, 2019, 12:48:22 amIf the supply is broken, isn't it easier to repair it? If it is a power brick you could find a generic supply with similar specs from the usual suspects (Farnell, etc.). If it is an integrated board then you are unlikely to find anything and repair is likely a much better option.

author: Armadillo
author_rank: Super Contributor
timestamp: January 26, 2019, 01:42:11 pm
content: Quote from: janoc on January 26, 2019, 01:38:13 pmAnd you, don't be a Bastard Idiot here as if you know all, smart alex!. Hahahahahahahaah

author: janoc
author_rank: Super Contributor
timestamp: January 26, 2019, 01:46:16 pm
content: Quote from: Armadillo on January 26, 2019, 01:42:11 pmWay to go, dude. Enjoy your shitty hardware then.

author: Armadillo
author_rank: Super Contributor
timestamp: January 26, 2019, 02:15:28 pm
content: Well, guys, I tried;Already given an awareness and obvious hint: "power supply adapter for Yamakasi Leonidas 30" LCD monitor". It's not easily available, not all shops carry it, not even in China. That's why some people would resort to buy the way they NEED to buy it, some people don't repair it, because they have reasons not to repair it example they have lost it.unruly lack of compassionate behaviors coupled with bad mouth..... what else to say......

author: hpapagaj
author_rank: Contributor
timestamp: February 05, 2019, 05:07:46 pm
content: Few days later:2 same diodes dead.1 capacitor dead.1 fuse dead.

author: Viljeri
author_rank: Contributor
timestamp: February 05, 2019, 05:46:16 pm
content: Hey just wondering did you fix the screw holding the mosfets like it was said here before or not?

author: hpapagaj
author_rank: Contributor
timestamp: February 05, 2019, 05:47:47 pm
content: Of course I did, the plate not touched the wire link on the PCB anymore.