# Let's Fix It: Table Lamp Problem !!

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## Introduction: Let's Fix It: Table Lamp Problem !!

Lets say I ran into a problem.

The table lamp I was using is not working anymore.It is a charging model which means it runs on battery after charging.The problem am facing is that even after charging the lamp is not working.Before throwing it away as junk lets see if we can fix it.

### Teacher Notes

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## Step 2: Lets Have a Look Inside !!

Using a screw driver with appropriate head unscrew every screw that it holding this thing together.
Be gentle which opening the frames.
After opening the frames you should see the battery and the circuit itself.

## Step 3: Understanding the Circuit.

The circuit can basically be subdivided into two small circuits-
1.Full wave bridge rectifier.
2.RC circuit.

Full wave bride rectifier
Before going into depth lets us get used to with the terms.
What is a rectifier?
-In electronics a rectifier is a component which converts AC signal to DC signal.

Here,we have the 4 diodes which are the rectifiers.But the arrangement in which they are connected is called a full wave bridge rectifier.
Looking into the matter,a fullwave bridge rectifier converts all the negative part of an AC signal into series of positive part which can be converted into DC later.

RC Circuit
Here,the letter R and C stands for resistance and capacitance.
So therefore is the combination of resistance and capacitance circuit.
The main purpose of using this circuit is to estimate how long the battery will charge.
The time constant (T)=R*C
which determines for how long the battery will charge.

Reference-http://www.electronics-tutorials.ws/rc/rc_1.html

## Step 4: The Hidden Problem...

After investigating a bit carefully,it was found that there was a loose solder joint across the capacitor and the PCB.
After completing the connection,the lamp was back is action.

CAUTION: Be careful while soldering the capacitor joint,make sure you don't short circuit the AC terminals.
It is dangerous and can kill you .

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Untill next time.

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## 2 Discussions

Nice repair job. It is remarkable how many broken electronics are just a simple loose solder connection.

Thanks mate.