Now we have found how to detect the faults of 4 components in the previous chapter. In this chapter we will consider how to detect fault in 4 other components. The 4 components are, the pin charging port, the USB charging port, the keypad, and the screen.


Many Nokia phones uses this pin charging port along with the USB port. Other phones that uses the pin charging port are the Chinese MOS phones. It is really easy to know if a pin charger is bad and needs a replacement. Here are a few stuff you can try.

Detecting The Fault

* Charging is unstable and battery level hardly increase if ever it does. This could be a sign that the charging port is bad.
* Plug in a working pin charger. If it does not charge at all, the a replacement is needed
* Look through the hole of the pin charging port and see if you will find a tiny pin inside. If not, it is bad.


In chapter 2, we learned that the work of the USB port is more that just charging a phone. This make it a little complex that the pin charging port whose job is simply to charge a phone. The most common USB port in use today is the USB 2.0. Our consideration of how to detect a USB fault, Unless otherwise indicated, is based on the 2.0 USB.

Detecting The Fault

* Check if the USB charger is working. Charge the phone with a working USB charger. If not charging, then the USB port may be bad.
* Change your battery. If your battery is dead, a working USB port and charger cannot charge it up. Be sure you are working with a good battery.
* Look through the opening in the USB port to see if it’s broken. If it is broken, it won’t work.


There are two ways keypads are designed in a phone. Either they are printed on the main PCB, or they are printed on a different PCB and attached to the main PCB by soldering or by clipping. It really does not matter how they are designed, they have the same way of working and the same way of detecting their faults. Something to take note of is the Nokia keypad connection system. Nokia phone keypads are connected to very tiny ICs which makes it a little hard to work with. On the surface, the methods below can help you detect a fault in the keypad of any devices.

Detecting The Fault

* Keypad hard to press
* Keypad easy to press but no corresponding display on the screen


Also in chapter 2, we said that the screen has white leds at its back that illuminate the screen. Sometimes, these led get spoilt or lost connection with the PCB. Under these conditions, the screen will continue to display its information but there will be no light to illuminate it, you will only notice a blank screen. But again, if the screen is bad and cannot display any information while the leds are working, only a bright white color display will be seen on the screen when the phone is on.

Detecting The Fault

* If the phone displays white background without any information
* If there is a crack on the screen or it get broken
* If the device turns on, can make and receive calls with it but displays nothing.

In all the above, a replacement screen is needed to solve the screen problem. How to fix the faults in this and previous chapter will be considered in the next chapter and the one after it.

So far, we have considered how to detect the faults of 4 more components. But what  if a phone refuses to turn on? If the SIM sit does not work? And what if a faulty component was replaced but the same problem continues? All these are common issues expert technicians faces every time and you should know how to handle such situations. In section 2, more on these will be considered.