hath wroth:

A flatbed scanner instead of a camera might work better, consistent
scaling.

It won't. A scanner has a very narrow depth of field. If there is
anything between the scanner glass plate and the board, it will cause
the board to be out of focus. I've tried it and it doesn't work.

I use a digital camera to take photos of both sides of a board. I
then use a photo editor to flip over, convert to a transparency, and
eventually create a composite image. If I'm ambitious, I play with
the colors sufficiently to remove the uniform board and trace colors,
leaving only the components. Then, it's easy to just connect the
dots.

If I'm really ambitious (or have lots of time), I import the component
layout BMP into a CAD or PCB layout program, overlay the components
with component symbols, overlay the connect the dot traces with rubber
bandable lines, and then drag the components into something resembling
a schematic. I recently did this with the glow plug control box for
my diesel truck, which was very simple. I don't recommend this method
on anything complicated.

A few years ago, I inherited a large pile of boards without
documentation. I wanted to get them working and had to generate a
schematic. It was tough because of the large number of SMT parts. So,
I sacrificed one board, used a propane torch to remove the components
(on both sides), and ended up with a bare board. Much easier than
trying to trace the board with the components in place.

Incidentally, there are companies on the internet that advertise
circuit board reverse engineering services. If this is a complex
board, you might want to get a quotation before attacking. For
example:
http://www.armtec.net/circuit_reverse_engineering.shtml
http://www.cadx-pcb.com/CADX_ReverseEngineering.html
(many more...)


--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558