Electronic PC Board Recovering Without Schematic drawing

Electronic PC Board Recovering Without Schematic drawing is a process to rework the malfuntional printed circuit board in the absence of schematic diagram especially for those obselete circuit boards.

When try to recover electronic circuit board in the absence of its schematic diagram, especially when this electronic Circuit Board is relatively strange to the engineer, according to previous experience, even if a veteran PC Circuit Board repairing engineer won’t be able to fix this issue promptly and smoothly, hereby we list some of the main principles that can be followed when try to repair a one to increase the working efficiency:

First of all, monitor target electronic PC board and then measure it, the tools should be applied include the multi-meter and microscopy, the good habit to handling an electronic PC board ready to be recovered is monitoring it, by using microscopy can check if there is any break-off of tracks on the Printed Circuit Board;

And if there is any break-off phenomenons can be found on the negative parts such as resistor, electros, transistor, diode and triode; and the most important thing is if this electronic PC board had been repaired before.

If yes then which components had been touched or moved? Is there any mis-conduct such as false soldering, cold soldering or reverse insertion, after confirming there is no such case, need to use multi-meter to test the resistance value among the power supply and ground, normally this value of resistance could be around 70 to 80 ohm, or above,

if the resistance value is too small, only a handful or a dozen of ohm, there could be some of the components have been breakdown,

then it is necessary to find out the breakdown components from the Printed circuit boards, and the method is power on it, and feel the temperature of each one of them, and those with extremely high temperature will become suspected item.

And if the resistance value is normal, need to measure the value of each part such as resistor, diode, triode and MOS-field effect tube, switch.