suspicious too cheap switching PSUs - Page 1
Forum section: electronics / general

author: legacy
author_rank: Super Contributor
timestamp: September 28, 2018, 04:02:30 pm
content: so, I am observing a couple of switching PSU modules on eBay and ePrice, and they appear too suspiciously cheap.60Watt 12V DC @ 5A for 4 euro? Umm, a product with the same characteristics (low ripple, no noise, etc) is being sold by Omron for 20 euro.I can't judge by a picture, I am tempted to buy one of those cheap units and to analyze it.What do you think guys? any experience?

author: HB9EVI
author_rank: Frequent Contributor
timestamp: September 28, 2018, 05:14:34 pm
content: The cheapies I got so far in hands were all missing essential parts and had obvious design lacks; missing parts are input filter caps, common modes chokes, PFC correction coils, poor quality electrolytics, which even blew up under nominal load a.s.o.

author: Terry01
author_rank: Frequent Contributor
timestamp: September 28, 2018, 06:24:43 pm
content: "4 euros" is an ok price if you get a decent pyro effect off it when it blows? Maybe the Mrs won't see it that way though so best not to if there's a high possibility it will catch fire!

author: kripton2035
author_rank: Super Contributor
timestamp: September 28, 2018, 06:30:59 pm
content: as with many cheap chinese stuff, expect at best to have half what is claimed.

author: Bud
author_rank: Super Contributor
timestamp: September 28, 2018, 07:10:05 pm
content: That is right, having a ps blew up at 80% of its labeled power rating on me. Divide by two for safety. Also garanteed lower quality electrolythics and questionable quality semis. Shitty soldering, almost forget to mention.

author: HB9EVI
author_rank: Frequent Contributor
timestamp: September 28, 2018, 07:15:24 pm
content: If possible, watch out for Delta or Meanwell devices; they are not too expensive, but rather good quality

author: legacy
author_rank: Super Contributor
timestamp: October 01, 2018, 04:54:38 pm
content: Here it is. Do you see anything weird? Any clue? This PSU was purchased for 4 Euro by my colleague. He said he is willing to give it a tryShould we be worried ?

author: legacy
author_rank: Super Contributor
timestamp: October 01, 2018, 04:58:44 pm
content: Quote from: HB9EVI on September 28, 2018, 07:15:24 pmYup, I will. But the PSU must be within 110(B) x 78(C) x 37(A) mm.

author: Mr. Scram
author_rank: Super Contributor
timestamp: October 01, 2018, 05:14:30 pm
content: Quote from: Bud on September 28, 2018, 07:10:05 pmBy "devide by two for safety" you mean cutting the PSU in half, right? I don't think any derating can make these safe to use.

author: schmitt trigger
author_rank: Super Contributor
timestamp: October 01, 2018, 05:32:10 pm
content: In addition to what others have mentioned:One of the usual faults for these cheap supplies is that the creep distance between the hot primary side and the secondary side is routinely violated.At least this unit shows that the PWBA has some slots to prevent that, to some degree.But we don't know how the transformer was wound.Another is that the EMI-reducing capacitors are too large allowing excessive leakage current.Do you have access to a hipot tester? I would at least do a test to determine whether a shock hazard exists or not.

author: CJay
author_rank: Super Contributor
timestamp: October 01, 2018, 08:22:22 pm
content: Quote from: blueskull on October 01, 2018, 05:42:45 pmIt looks surprisingly good, the component leads look the 'correct' thickness, most of the components don't look cheap (capacitors don't look great), there's an insulation sleeve on the main reservoir cap, isolation cutouts in the board and the board material looks decent quality, it's had some attention to detail, I think I'd be happy to give that a try.

author: ebclr
author_rank: Super Contributor
timestamp: October 02, 2018, 01:01:29 am
content: I used a similar power supply to power my homemade t12 solder and is working fine for more than 4 years, You don't need name brand components, to have a decent power, Name brand can increase quality for sure, but the price will increase exponentially while quality will increase in fractions.KISS

author: Mr. Scram
author_rank: Super Contributor
timestamp: October 02, 2018, 12:57:14 pm
content: Quote from: ebclr on October 02, 2018, 01:01:29 amThe power supply could work fine and function for a while or even years. It could also burn your house down. That's the thing. You just don't know.

author: schmitt trigger
author_rank: Super Contributor
timestamp: October 02, 2018, 04:51:31 pm
content: Exactly!When CFLs came out about 20 years ago, they were expensive, $8US or more.Then I found some units on the dollar store which were exactly $1US apiece. I immediately bought units for the whole house, over 20 units.The light was a little weak, but hey, what can you expect from $1US.One evening I was working on my computer, when there was a loud bang and smoke started pouring from one of the lamps.I immediately turned off the light, and after a while I removed the lamp.Of course, an autopsy was made. Turns out there had been a short between the pair of AC lines, and the PWBA, a cheap paper phenolic type, started to burn. Later I tested the plastic enclosure and it also burned readily. No flame retardant of any type.If it had been my wife in the room, or would the room had been unattended, something really bad could have happened.Afterwards, I removed and discarded all the other lamps.NOT SAYING that this particular PSU of yours will burn. Only saying that to achieve a certain price range, shortcuts are made.

author: ebclr
author_rank: Super Contributor
timestamp: October 03, 2018, 06:07:33 am
content: "It could also burn your house down. "The probability of this happen is lower than Trump makes America great again.