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I have a PCB containing a power amplifier. I want to extract the schematics from it. It would take a few good hours, but it is achievable. Is there a tool to help me speed up the reverse engineering work?

In the end, I extracted some 80% of the schematics by processing the picture in PaintShop Pro, but I want to optimize the process for the next time... So, the question remains open (and it is not specific to this particular PCB). My hope is that maybe some dedicated software exists for this purpose.

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    \$\begingroup\$ Easiest? Or cheapest? Because easiest is an x-ray...but I'm guessing that's not an option. \$\endgroup\$
    – DKNguyen
    Dec 28 '21 at 15:04
  • \$\begingroup\$ I'd use kicad. Position components on pcb. Make connections on schematic. \$\endgroup\$ Dec 28 '21 at 15:17
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    \$\begingroup\$ If I gave you a cake and asked you to extract the recipe what would you do? Hint: the recipe doesn't exist inside the cake (i.e. it's unextractable) so, you have to do this by hand. \$\endgroup\$
    – Andy aka
    Dec 28 '21 at 16:03
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    \$\begingroup\$ Does this answer your question? Is it possible to extract pcb layout from an already made PCB? \$\endgroup\$ Dec 28 '21 at 18:52
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    \$\begingroup\$ Watch how Big Clive does it with (flipped) photos. I also find a few cups of strong coffee useful. \$\endgroup\$ Dec 28 '21 at 21:28
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Take good photographs (If single sided, use a light box) then scale, flip and combine the two photos of the sides of the board so you have a picture showing the copper AND the components.

It is not a horrible idea to doctor the photo of the copper so that the copper shows up in some garish colour before merging the pictures.

If more then two layers you are in for some pain.

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  • \$\begingroup\$ +1 flatbed scanner works very nicely too \$\endgroup\$
    – bobflux
    Dec 28 '21 at 15:59
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A method I've used in the past is to take a picture of the PCB and then import the picture into a schematic capture program. You can even draw components and wires over the picture of the PCB. Once you are done you'll have a bad looking schematic (because all the wires will be mixed up with this location on the PCB). Copy the schematic or remove the picture, and unscramble the schematic.

If you are working with a 4 layer board you can x-ray the inner layers.

Another thing I did was use Visio to take a picture of the top and bottom of the board and then overlay both top and bottom pictures to help draw wires.

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When ordering a professional PCB, you can pay for a Flying probe test (wiki) which basically checks how each contact on PCB is connected to other contact (in order to check if PCB was manufactured without errors). This same machine is perfect for automating your problem in an easy way.

  • First remove all components with heat gun (removing components is very useful since you can take a look on bottom side of IC which might have labels on some china-made components).
  • Then perform automated contact test.

A few more things to note:

  • Looking at traces by eye won't work on PCB with inner layers.
  • Testing with multimeter while components are on PCB is dangerous since resistance is usually measured by applying 3V or so to the probes, which will easily damage sensitive components.
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    \$\begingroup\$ Isn't overkill to remove all components and then put them back? All this only to get the schematics???? \$\endgroup\$
    – Gravity
    Dec 28 '21 at 17:17
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    \$\begingroup\$ It sure seems that way, but once you start tracing a big PCB by hand, after a few hours of not being able to see the traces you'll wish you removed all the components at the start. :) I've tried to give answer that's helpful for someone with surface-mounted PCBs as well, in which case removing the components is the only option to see traces. \$\endgroup\$ Dec 28 '21 at 17:41
  • \$\begingroup\$ When in doubt, you'll want to use multimeter to see if trace is connected, which can burn sensitive components. Which is not the issue if you removed them all before (at least remove non-passive ones). \$\endgroup\$ Dec 28 '21 at 17:44

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