I Have the Power

A gadzillion years ago during my first week in Namibia still undergoing training in Windhoek I bought a variable AC-DC power supply from the Tre Supermarket on a whim (and in the hopes my radio would pick up the World Service and I could power it from the mains, it didn’t and I couldn’t).

This was a shiny white box with all sorts of different outlet connectors and quite decent. It did 3-12VDC at around +3% (12.4V for the 12V setting).

When my mate John’s switch supply blew at the Ministry of Youth I foolishly lent him my shiny supply.

A while later he blew it up. Causing some impressive scorching on the inside.

Luckily I had just been gifted another variable supply so failing to learn my lesson and with the youth of Opuwo facebookless I lent him another.

Which he blew up.

As I was now entirely out of supplies and nobody fancied my suggestion of jury-rigging the 12V bus of a hot-wired PC power supply he bought a replacement for himself and one for me.

Did I mention my original one was quality and gave accurate output?

Today I had potential need for another supply (see below) so took it out of the box and before blindly plugging it into anything tested the output and polarity. The polarity was correct to the setting but the output was a little off.

Dodgy Variable DC Supply - 17.7V on 12V Setting

Here it is on the 12V setting giving 17.7V. Nice.

You don’t just get what you pay for – you get more! Probably too much more.

To be fair though on the 9V setting it gives around 11.8V which should be good enough for 12V equipment.

No AC/DC for the Red Cross

The reason I dug out the supply was because the Red Cross ADSL router wasn’t working, no lights showing (technical term is knacked).

With the recent thunderstorms and spate of PSUs I’ve been replacing recently I thought it was probably just the transformer and planned to use Mr Overvolt as a temporary replacement.

Testing their power supply against VDC caused a brief display and then nothing leading me to conclude it was the supply.

But wait, what’s that on the bottom of the router for the input supply? 12VAC. AC? Surely not, a misprint of course.

Check the power supply that has been working with the router until now and, um, it’s an AC-AC transformer (230VAC to 12VAC).

Put the multimeter on the right setting and the power supply is fine, 15VAC (looks like they’re all at it) but steady AC nonetheless.

So this means the router itself is creamed.

But on the plus side I got to see my first ever (and hopefully last ever) low-voltage AC supply.

230VAC to 12VAC Adapter

Really? What’s that all about?

I get the benefit of AC for transmission and for high-voltage or high-load appliances but at 12V and 1A? Also there is no way whatsoever all the components in the router (if any) use AC so I’d guess the very first thing inside is a bridge rectifier.

Are Huawei just having a laugh? Found a very cheap supplier of the rare AC-AC transformers? Hate people being able to replace power supplies easily when they blow?

Curiously my Huawei router (HomeLife a.k.a. HG520b) is DC as is the work Huawei MT-330. Madness.


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