Twin USB Mains Adaptor/ Charger with suppression

Masterplug Surge Protected Twin USB Mains Charger with pass-through mains socketI stumbled across this USB Mains Adaptor from Masterplug which boasts several handy features: firstly it has twin 5V 1,000mA USB sockets into which you plug your choice of USB lead, so you can charge two devices at once. Handily it also has a pass-through mains socket so you don’t lose the use of a mains outlet.

Unlike other chargers, this adaptor also has mains suppression to help protect your precious phone(s) from damage caused by e.g. motors, surges or the effects of lightning. Once a suppressor "blows" then the unit should be discarded.

It sports two garish LEDs indicating that power is on and the suppressor is intact. The unit is sealed for life and there is no accessible fuse carrier.

The Masterplug SRGAUSBPB (black) or SRGAUSBPW (white) Surge Protected Mains USB Charger is available from Amazon, Argos, B&Q, ebay and more for approximately £9.

Unfortunately, my first one failed because it wasn’t that good a fit and the earth pin got pushed inside! The replacement has been fine so far.

Startech USB Combi lead has mini and micro connectorsYou might also like the Startech USB Combo Cable – it’s a useful Mini USB and Micro USB to USB lead that you flip over depending on what size your phone needs.

The lead is available in black or white, see http://uk.startech.com/Cables/USB-2.0/Micro/3foot-USB-to-Micro-USB-and-Mini-USB-Combo-Cable-A-to-B~USBHAUBMB3. I also spotted it for sale on Amazon, but typical ebay seller prices were silly so don't pay over the odds.

Update on Wednesday, October 9, 2013 at 1:51PM by Alan W

Pass me that screwdriver...

Internals, showing the suppressors (blue MO varistors, heatshrunk) and gas discharge tube to earth. In fact two fuses are onboard as well.I wanted to know why the Earth pin of one of mine sank into the plastic body. The charger's tamper-evident label concealed a tamperproof screw, so a quick twizzle and the case was prised open (invalidating the warranty).

Only take switched-mode adapters like this apart after allowing plenty of time (e.g. overnight) for high-voltage components inside to discharge, and even then be wary of high voltages lurking within. I've fried a fingertip this way before now.

Generally the construction is far better than many Chinese ones I've seen. My photos (click them to view) show the suppressor components. There are two MOVs (Metal Oxide Varistors) and also two fuses (F1 and F2 on the silkscreen) all heatshrunk together. A Gas Discharge Tube (GDT) nearby connects to Earth. When the suppressors are intact an l.e.d. glows.

Earth pin solder joint (circled) on p.c.b. Click to enlargeWhen fitted together the Earth pin is held in place laterally in all directions by the plastic moulding. However it's soldered to a thin strip (only) of p.c.b. copper foil which is subjected to insertion forces of the Earth pin. A small spigot of plastic on the cover therefore clamps the Earth pin down when the case is closed up, to "brace" it.

I guess mine had a dry solder joint and the Earth pin came away from the p.c.b., or that section of the p.c.b. broke altogether.

Something to bear in mind, the Earth assembly is not hugely strong so don't be rough with it when you're plugging it into a mains socket.