TROUBLESHOOTING IN MOTHERBOARD
The motherboard faults are the most challenging ones. Diagnosing its faults requires great patience. However, 80% of the problem can be detected using the DIAG CARD. But it would only give you an idea of which signal is missing accordingly to which the actual problem has to be traced out. Some of the basic faults found in motherboards are:No Display:
The board is physically checked for any damaged. Any physically damaged parts are replaced with new ones.
Check the 3V battery. If low, replace the battery.
In cases the problem is due to improper CMOS setting, clear the CMOS with the help of the CLEAR CMOS jumper.
Check to ensure that the jumpers pertaining to CPU speed (i.e. base frequency & multiplication factor) are correct as incorrect settings may result in over clocking of the speed.
As the first step, the existing BIOS is changed with a reference working one & the board is re-checked. If the problem was with the bios, it will be solved. The original BIOS is re-programmed.
If the BIOS is not a problem, the main controller IC is checked for shorting of pins & for any physically damage. The shorting, if any, must be removed.
If the main controller IC is dry-soldered, it should be touched up.
Lastly, if the board is not working, the main controller IC is replaced. This will definitely solve the problem.Continuous Reset High:
The reset signal on the board remains continuously high because +5V is not coming on the reset pin. Due to this, the clock & the other signals are not generated.
Firstly, the voltages on the reset pins of the external connector are checked.
One pin has to have +5V& the other ground.
Mostly the +5V pin carries less voltage. In this case, an external wire jumper is connected from pin b3 of the slot to the pin. Connecting the wire jumper solves the problem in most of the cases.
If this does not solve the problem, we check the voltages of the different regulators on the board. If any one is found fault