Monday, November 28, 2011

Hacking Nokia Charger

My Charger for Nokia mobile stopped working yesterday.
so decided to give a try to fix the problem.

In the initial inspection itself i found that the very first stage (high voltage bridge rectifier) is not getting supply. Noticed that there is a very low resistance just before the bridge which is burned off. but there should be some reason for it to burn.

Then noticed that there are 2 electrolytic capacitors immediately after the bridge, and they are bit bulged out. they are rated as  4.4micro fared 400v. but size was too small for that rating. so it is very evident that Nokia charger fitted with an over rated capacitors which is suffering from internal short circuit.

Now bigger challenge is where can i get a replacement for this high rated capacitors!?
its not a big problem, i had a collection of burned out CFL lamps. every CFL lamp is equiped with such a bridge and a high voltage capacitor. so i pulled out one of such capacitors and and replaced it in the charger.

(I had an accident that i burned 2 diodes also in the testing, giving a mild explosion. but that also i could able to replace from discarded CFL ballast.)

Then i kept worrying where will i get a replacement for the burned out low resistances. since the resistors are rated very low, i decided to take a chance by short circuiting it. this OK because it is the first stage of conversion from AC line to high voltage DC. in fact resistors don't make any sense in this stage.

Then i went for a final testing and found that it is working like a charm.

Here is the overall experiment in nutshell:

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