Reverse Engineering a Schematic from a Circuit Board

instructables.com

29 pointscoderdude5 comments

I found most circuits are based on generic engineering designs. Note the chip numbers, get datasheets, and draw a basic block diagram. From that, draw up a mock diagram that could work, then reference the board for the details and make changes. The result is fairly accurate.

Yep, pretty much a waste of time on 4+ layer boards

So true.

I'd argue it's probably a waste of time on greater than 2 layer boards myself (having had the pleasure of doing this on a Telequipment D83 scope amp module) unless you want to boil them and get the laminated layers out and then don't even ask about vias.

What is even more of a pain about doing this is that on traces that carry high frequencies, intentional parasitic inductances and capacitances are sometimes designed into the board and there is no way on hell you're going to reverse engineer them.

If this is for reverse engineering and repair, it's best just to "replace at the border" i.e. replace the controller assembly with something electrically compatible much as they did when they went from relay logic to PLCs back in the 70s and 80s.

I think the pros use x-ray

You'd think so but they don't see through ground planes.

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