Hey internet, novice here.
I am trying to understand the concept of how circuit boards are built in hopes that this knowledge can help me understand how to approach the repair, and find the fault easier.
I've been repairing some stuff, looking at some diagrams, watching videos(of course) and learning.
But based on what I see so far, [b]let me run this by you.
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Basically, seems to me that, circuit boards are built around few ICs that are supposed to do the job.
The rest of the components are there only to transmit power and signal to these ICs, and away from these ICs.
If an IC needs 5v, and input into the board is 100v, there must be some components that can lower this voltage so IC can use it and not get damaged.
Lets say some type of a video device is not outputting any video.
I can then look at the chips inside this video device, see which one has the job to process/output the video signal, first test if it is even powered and then test its video output pins.
If the chip is not getting any power, the problem is with the power line leading to the chip.
Then I just narrow the problem down until I get to the issue itself (cold solder join,failed component,broken trace,...)
Did I get the concept right or am I missing something ?
Please, point me to the right direction where I can learn what I need to understand this better.
One important point, In addition to signals, and power there is also data storage. Some of the chips also contain data stored in them which is very specific to that board. If these chips go bad then depending on the chip, the board and the company that manufactured it you may or may not be able to replace them with a off the shelf replacement chip.
For eg: if on a computer motherboard if the bios chip fails then you can replace this chip with an off the shelf chip from the market and then program the chip with the same bios which is publicly available. But in some boards this might not be possible as the data stored on the chip could be proprietary or a standard user interface is not provided for the same. For eg: on the Raspberry Pi 4 the power ic (MXL7704) there are registers which store configuration information which cannot be accessed easily. So a straight forward replacement of this chip with another MXL7704 is not possible. And this is a major reason for quite a few RPI4s becoming a brick.
Another place where such chips are used is to store the encryption keys used by the device (eg: TPM chips) . Samsung uses this concept as a efuse to detect Knox Warranty voiding.
Long Story short, every board is unique and it has it own unique set of components on board. Each board has to be studied to understand the flow of signals/power on the board. Earlier this could be done by just looking at the board. But now with the introduction of multi layered PCBs it is impossible to trace a path by just looking at the traces on the board. A circuit/schematic diagram is a must. In fact nowadays even a circuit diagram does not help, you need a board layout diagram in addition to the circuit diagram as the boards have become so densely populated and components so tiny that it is very difficult to match the component on the board to the component in the circuit diagram.
Go thru Alex's videos, the sheer variety of boards he handles is amazing. And i am sure he does not know everything about every board he works on, but there are some basic rules of electronics that he uses identify the issue and resolve them. You can learn a lot of those basic principles by going thru them.
Hope this helps. Do try