Step 1: What and Why
In the radio, the voltage supply, is composed by :
This system is called "Output Smoothing" : principle : http://en.wikipedia.org/wiki/Image:Diode_bridge_smoothing.svg
The transformer supply 9 or 12 volts in AC, and the diode bridge transform it into DC, but there is always "variations" of current, then there is a capacitator to avoid this problem and have a stable DC.
A generator like this cost, approximately 20 â¬ -16 $ in an electronic store.
Step 2: Tools
-A brain (very cheap)
-An Iron Solder
-Multimeter : The most important thing
-Solder wire (I used Sn:99.3 and Cu:0.7%)
Step 3: Disassemble the Radio
Found the screws, and remove them, in order to open the radio. Here in my radio there's only 4 screws.
Then, open it and look for the transformer and the first 4 Cables. There is 2 output for 1 input.
Red - Yellow, and Blue-Yellow . But they aren't interesting right now. What is interesting right now is the diode brigde : next step
Step 4: The Diode Bridge
The diode bridge principle is simple, just type "Diode Bridge" in Wikipedia or in Google. It's real simple system.
But so, no theory just practice here :
The diode bridge is always present under this form :
4 Diodes (tiny black/grey) and capacitator (big blue piece). Try to find it and look for the contacts on the other side. I mean the capacitator have 2 poles + and - , which are in the bottom of the board.
If you get the voltage at diodes poles, the multimeter will show 3 v or 6 v ... because it changes ... at 50 hz !
In some radios or machines maybe you'll find another very little part between diodes, which are "inductors". But, in a simple radio-clock-alarm it doesn't matter.
Step 5: Get the DC Current !
An important law of electronics says that if you get the current you wont have 11.40 v but 11.40/2, if you still use the radio/clock in the same time.
Now we'll find the poles, and connect to them :
Mines are indicted by my finger .
Step 6: Mesures
Follow the circuit until another 2 poles of dc current and sold the wires there
I'ven't photos yet because i'ven't 4 hands " and the 3rd hand isn't photographer " . But simply put a little bit of solder wire on the existing pole and put the wire on, just like a simple soldering method.
/!\ Not for kids, Solder Iron is dangerous /!\
And be careful to don't destroy the radio
In the multimeter is show - 11.34 just because i've put the wires in the bad polarity. Nothing interesting. The voltage in DC is 11.34 V !!!
Next get 2 longs wires and sold' them to the capacitator and put the wire out of the radio (from a free hole for example) and assemble the radio, as you disassemble it .
Just enjoy this radio/clock hack !