Reverse enginner in PCB board

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pauloDNS

Joined Jul 19, 2020
17
Do you do reverse engineer on PCB board where you haven't schematic? how do you do it?
You only use paper and a multimeter or other things to do?
In my work, I have a lot of PCB board of inverter frequency to repair and some problem takes a long time and I haven't the schematic
 

Ramussons

Joined May 3, 2013
972
If you can identify the IC's, you can look up the web and get the basic application schematic. You can start building on this.
You will need paper, MMeter and IC data / app schematic.
 

anniel747

Joined Oct 18, 2020
1,041
Do you do reverse engineer on PCB board where you haven't schematic? how do you do it?
You only use paper and a multimeter or other things to do?
In my work, I have a lot of PCB board of inverter frequency to repair and some problem takes a long time and I haven't the schematic
All depends on the complexity of each PCB. Pencil and paper for simpler ones and nodes based for more populated ones.
 

Dodgydave

Joined Jun 22, 2012
9,951
Start by looking up the chips or transistors on the web get the information on them, put the supply line in ,then draw them out on paper and link them together with the details from the pcb, resistors capacitors etc.

It can be time consuming and an headache at times, past experience and knowledge of specific components makes it easier.
 

metermannd

Joined Oct 25, 2020
189
My method:

Make a list of all the parts by designator and how many pins each has
Expand the list so that there is one entry per component lead
Pick a connector and start with pin 1, then make a list of all the leads that are connected to that pin, crossing off the entries in the list as you go along, then lather, rinse, repeat with the remaining pins on the connector(s).
A light to shine against or through the board, a magnifying lens, and even a multimeter are VERY helpful in this stage.
(If you know which traces are the supply rails and ground, start with those instead)
Then move on to the 'internal' traces that do not tie directly to a connector.
Eventually, the remaining pins in the list should be unused component pins etc.

Once you have made a list of all the nodes, you can use that list to build the schematic in your preferred EDA program (like KiCAD).
 

bwilliams60

Joined Nov 18, 2012
1,398
Depending on how many times I am going to see this circuit, I will do it one of three ways. A one time circuit will probably get drawn on paper. I draw it as it is laid out and then connect the pieces and if need be, I will draw it as a schematic but generally a layout is all I need. A second method would be to take a snapshot of the board and then put it in paint and connect it together if it is a simple circuit. My third method for something I will see more than once is to do it in KICAD. Although this becomes more difficult and you have to make a lot of symbols, it is good practice to use the software. Always complete a pathway from start to finish including all branches that come from it. I use my DVOM on continuity with the beeper to follow the pathways.
 

MisterBill2

Joined Jan 23, 2018
8,745
For single sided boards it often works to have a bright light behind the board and then trace out the circuit looking at the component side. This can also work for double sided boards, but slower.
Of course, for service work and repairs it is important to know what the board is supposed to be doing, and then observe what it actually is doing. Since most circuits have an input of some sort and a output of some sort, thracing in one direction or the other usually leads to finding the failure. But understanding what is upposed to be happening is very important.
 
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