In this video I test a Chinese 12V “2A” switching power supply designed for LEDs, CCTV, routers, etc. It cost me only $ 1.80 including shipping. The actual current capability is about 0.5A and the safety is quite questionable. It’s a classic 2-transistor switching power supply with an optocoupler, but it’s quite underrated, has poor mains isolation and misses basic safety features like a fuse.

Today I took a look at a very cheap Chinese 12V 1A adapter from Ebay. The listing says it is for LED strips, CCTV, routers, audio/video equipment, etc. This AC/DC adapter has 100-240V universal mains input and 12V 1A DC output. I took a look at the board layout, reverse engineered the relatively simple schematic of it and made an autopsy of the transformer. This power supply is quite dodgy – there’s no fuse, no EMI filter, no inrush resistor, no snubber network and a very questionable capacitor between the primary and secondary side. The isolation distance on the board is 1.5mm. I have seen more dangerous transformers, but also much safer ones.

What’s inside the Manson SPS9400 40A 3V to 15V Switchmode Power Supply?
Also known as the Jaycar Powertech MP3090 and BK Precision 1692

http://www.eevblog.com/files/SPS9400_ServiceManual.pdf

There are a few of these little power supply modules on ebay, so I thought I’d get one and give it a thorough test. Voltage holds relatively well, with just a slight drop under overload conditions, and the module layout and filtering is actually very good.

Comments:
A cheap chines pwer supply that is actually safe? and the thing even performs well! we have a miricle on our hands somebody call the pope!