Mains power board teardown - Page 1
Forum section: electronics / general

author: jfasoc
author_rank: Contributor
timestamp: March 09, 2016, 07:14:01 am
content: Calling it a teardown is perhaps a bit much but the first thing I did after getting a new power board was open it up to see how it was made. I was not exactly impressed. Or rather impressed if this is actually legal. I would be interested to hear from someone who know the standards around the world what rules are broken.

author: hamster_nz
author_rank: Super Contributor
timestamp: March 09, 2016, 07:22:49 am
content: Anyyhing you have in mind as being dodgy?Not sure if it is in the standards, but the tacking on of the protective earth wire to the metal strip is pretty bad. If that comes away it is a death trap.I always thought that it had to be a mechanical bond. E.g crimp lug and screw...Anything else could fail and it would be pretty harmless, but if that joint comes lose...

author: fantis1337
author_rank: Contributor
timestamp: March 09, 2016, 07:53:25 am
content: You'd be surprised how many dodgy and flat out dangerous power boards are CE marked. When you get those sockets that are extendable via bus bar they always seem to have an exposed end. Once you see inside one where the wires are plugged in rather than soldered you can't help but to think how crazy some designers are.

author: miker7940
author_rank: Contributor
timestamp: March 10, 2016, 07:25:51 am
content: Quote from: fantis1337 on March 09, 2016, 07:53:25 amRemember there is a difference between the CE and the China Export/Can Electrocute...

author: mmagin
author_rank: Frequent Contributor
timestamp: March 10, 2016, 11:40:15 am
content: What are the three terminal devices next to the outlets? If they're switches, why does the earth ground line go to them?

author: Richard Crowley
author_rank: Super Contributor
timestamp: March 10, 2016, 11:52:16 am
content: Quote from: mmagin on March 10, 2016, 11:40:15 amWhile @jfasoc did not post a photo of the exterior, it seems pretty clear those are probably small, round rocker-switches.It seems traditional outside North America to provide a local switch at each receptacle.It appears that in the "OFF" position, it connects the line/hot pin to neutral/low (blue).It looks like the earth/ground (yellow/green) wire goes directly to the receptacles.I am also surprised at the soldered earth/ground. That would probably NOT pass inspection by the authorities.However the sorry appearance of the internal wiring is pretty common if you open those things.

author: jfasoc
author_rank: Contributor
timestamp: March 10, 2016, 03:19:40 pm
content: The top exterior looks as below. The 3 terminal device is indeed a switch, with light when the power is on. I guess that should be the only reason neutral is connected to it.This is not CE marked. It was bought online in China from one of the biggest online sellers. It is a fairly big European brand.

author: Richard Crowley
author_rank: Super Contributor
timestamp: March 10, 2016, 04:48:27 pm
content: Quote from: jfasoc on March 10, 2016, 03:19:40 pmAh! So that explains why neutral is also connected to the switch (for the light).FWIW, connecting the neutral (blue) through each and every switch connection all the way to the far end of the receptacles is probably the worst possible scenario. All the current must go through each and every one of those solder connections to reach the load(s). Horrible design.

author: SeanB
author_rank: Super Contributor
timestamp: March 10, 2016, 05:20:39 pm
content: You mean anything in addition to the solder being used as a mechanical connection, and a pretty poor one at that, just waiting to fracture from stress or vibration and spring mains connected wires across any point in reach. Going to bet as well the wire is copper coated aluminium as well, the stuff does solder somewhat, but the fatigue life is terrible, especially if you are thinking of doing something like using the flexible cord as an actual flexible cord and moving it. Plus the plastic that is likely to degrade into a brittle mess within 2 years if exposed to light or any heat over 5C.

author: mmagin
author_rank: Frequent Contributor
timestamp: March 10, 2016, 06:55:30 pm
content: Oh, haha, I saw blue as green because I was wearing my orange glasses reading on my tablet in bed (to cut blue light and avoid interference with sleep). Makes more sense now.

author: station240
author_rank: Unknown
timestamp: March 10, 2016, 07:08:45 pm
content: I count two stray strands at the switch ends of the brown wires (active). Also the cord clamp is barely gripping the mains, yank the cord 1cm and it will only be around the individual wires (ie not gripping).Everything else is exactly what I have inside my small UPS.

author: Someone
author_rank: Super Contributor
timestamp: March 10, 2016, 11:41:49 pm
content: Quote from: hamster_nz on March 09, 2016, 07:22:49 amIts sure is in the standards, either mechanical bonding or doubly redundant and over engineered soldering (which some recent tear downs on the eevblog have shown aren't even being followed even by test and measurement manufacturers).