Electrocution risk - Swees USB power supply - Page 1
Forum section: electronics / general

author: bktemp
author_rank: Super Contributor
timestamp: April 08, 2016, 06:45:58 am
content: Except for the faulty transformer and the obviously missing quality control at the production, it looks pretty decent. I have seen much worse power supplies.

author: Ysjoelfir
author_rank: Frequent Contributor
timestamp: April 08, 2016, 07:57:11 pm
content: I actually don't like the Swees stuff. Just today I sent back the third Swees DAC I got. The first one did its job for around 2 months, the second one 3 months, and this third one now for about 2 weeks. I am hoping for a refund now.

author: VK3DRB
author_rank: Super Contributor
timestamp: April 09, 2016, 12:01:30 pm
content: It is most likely the manufacturer knew of the problem in the batch and if they didn't, they were just plain incompetent. If the manufacturer has any brains or any morals, they would have rejected the entire batch of transformers. Did they do any hi-pot testing? To what standards? Was it UL or CE marked? Where is the recall?I bet it is made in the People's Republic of China, where safety is of no concern if it gets in the way of making money for the factory owners or corrupt government officials.

author: SeanB
author_rank: Super Contributor
timestamp: April 09, 2016, 01:23:44 pm
content: Doubt those transformers are machine made, more likely a line of workers who each do a single set of operations along the line, or who all run in parallel doing them.

author: amyk
author_rank: Super Contributor
timestamp: April 10, 2016, 12:19:51 am
content: Probably not a widespread issue but a random one-off. The transformer is otherwise well-designed and so is the rest of the unit. Small wire damage has caused accidents with far more expensive and critical equipment; even aerospace is not immune:https://www.eevblog.com/forum/chat/another-dreamliner-fire/msg464503/#msg464503

author: wraper
author_rank: Unknown
timestamp: April 10, 2016, 12:54:45 am
content: Quote from: VK3DRB on April 09, 2016, 12:01:30 pmHow do you know that was problem with a batch? This might be one defective transformer out of 500 000 as well. Also, this particular design is sold under many brand names.

author: VK3DRB
author_rank: Super Contributor
timestamp: April 10, 2016, 01:07:11 am
content: Quote from: wraper on April 10, 2016, 12:54:45 amHow do you know is wasn't. I doubt Amazon is going to tell you.This problem could have killed someone. The fact that ONE got through means it is one too many. Good processes would have ensured this would never have escaped the manufacturing process. In addition, a good design would have employed a second means of user protection, but these days everyone wants everything cheap. I worked in an IBM plant that manufactured millions of IBM PC's, all using switch mode power supplies. Every machine was hipot and earth leakage tested. ZERO reports of electric shock from the field in 15 years of manufacturing.Not long ago a woman in Sydney bought a dodgy Chinese iPad charger. She was electrocuted by it.Trying to get more for less comes at a price.

author: wraper
author_rank: Unknown
timestamp: April 10, 2016, 01:35:52 am
content: Quote from: VK3DRB on April 10, 2016, 01:07:11 amI didn't assume anything. Just noted that you made the statement as if it was a known fact that whole batch contained defective PSUs, but without any information to support this assumption.

author: wraper
author_rank: Unknown
timestamp: April 10, 2016, 02:54:01 pm
content: Quote from: VK3DRB on April 10, 2016, 01:07:11 amSo please tell what are those second means of user protection? Grounding does not count as it changes the class of the device and is not available in every socket.

author: coppice
author_rank: Super Contributor
timestamp: April 10, 2016, 03:34:31 pm
content: Quote from: wraper on April 10, 2016, 02:54:01 pmMaybe he is thinking of linear supplies. With mains transformers its quite common to use separate plastic bobbins for the primary and secondary. With SMPSes, even medical grade supplies look little different from the one under discussion. Look at the one Dave tore down a few months ago.