Failing Electronic : Sinking Currents

[Metropolitian]

A few months ago I posted  about an phone charger (usb adapter) that has failed.

I will, at times, post such topic to (dis)amuse you my fellow readers. ????

 

This time: An 'switching power brick'.

 

An electronic store with a service center clears their stock with returns and no-claim products every couple of years along with an clearance sale.

A few years ago I've bought a carton filled with 'disqualified' products.

Inside the carton that I filled with a few small audio amplifiers and inverters which I got for their aluminum casing for some of the DIY projects. (Bought cheaper then when buying the case alone.)

Even found some led strips with adapter and remote, sometime the adapter was missing and sometime the remote. I went for the led strips.

 

Now I opened one of them, the one with the adapter.

Switching Power Supply.  12 V, 2 Amp. It reads on the label.

 

 

I was amazed with the weight of this 'brick' as it felt like was filled with feathers and helium, compared with other power bricks which are quite modern but not as heavy as the original Commodore bricks. ????

 

I connected this to one of my projects which needed 1 amp at least.

The device barely turned on before collapsing. I measured and it was 12 volt. Connected.. the voltage dropped.

Tried another 'good' adapter, the device turned on fine.

 

Hmm.. something suspicious with this thing.

 

I opened it. And what I found inside.. no feathers but..

 

Jawdropping... It's an re-purposed phone charger ! (Note the USB Plug an the cut off red wiring)

 

The main wiring is soldered on the solder side as well as the DC wires.

Instead of using the trough holes where still two short pieces of red wires are.

 

In phone chargers the board is connected with either wiring to the prongs or with a flat spring, like this one:

Picture: good working board from a phone charger. 5v, 500mA.

 

What they did with the modified board was cutting out the zener diode which normally clamps the rectified output of the transformer to 5 / 5.2 volt.

By their 'luck' the output of that without the zener was 12 volt, but once a significant current was used the voltage would drop.

With the zener in place and 5 volt output, the current would never been 4 or near the 2 Amp.

5 Volt and 500mA is common for that setup without having the voltage dropping.

 

The adapter works fine with a small string from the led strip, but when using all colors as it is an RGB strip with remote control the string brightness dropping and sometime the controller turned off.  I understand why that product was returned to the store.

 

Some things amaze me. This was one of them.

[Crossy]

Not just Thailand.

 

Sadly the photo is long gone but a mate in Malaysia sent me a picture of a computer power lead he had bought "cheap".

 

It had a moulded Schuko plug, since Malaysia uses UK BS1363 plugs he cut off the Schuko intending to install a UK plug.

 

However, the cable was revealed to have six rather thin cores, very much akin to an RS-232 data cable!

 

It went in the bin. 

[Metropolitian]

17 minutes ago, Crossy said:

Not just Thailand.

 

Sadly the photo is long gone but a mate in Malaysia sent me a picture of a computer power lead he had bought "cheap".

 

It had a moulded Schuko plug, since Malaysia uses UK BS1363 plugs he cut off the Schuko intending to install a UK plug.

 

However, the cable was revealed to have six rather thin cores, very much akin to an RS-232 data cable!

 

It went in the bin. 

UK BS1363 the plug is fused.

Guess with the Schuko plug, they use the cord as fuse ????

 

Met some of those cables for the computer, I bin them and replace them for a UK or Australian power leads, which has the right core sizing.

(Have cut'd some of those to check)

You can find these for 10thb only at Zeer, as Thais have 'no use' of them..

I keep using them complete, some of the outlets here (extension cords) accept UK plugs or I cut off the plugs and use the cable itself.