Nothing is more frustrating than spending an hour or so tracing both sides of a double-sided PCB, drawing it or noting routes on paper, only to find that somewhere, you mistakenly traced a different track when flipping the board.
A lightbox below the PCB can assist in seeing the opposite side's 'mask-shadow' of traces, but SMD or large comopnents may block some tracks.
A ruler or vernier can be used from edge of board, or known holes /cutouts.
Remember, when board is flipped, the 'image' layout is also inverted, either vertically or horizontally.
Where a PCB has lots of closely-spaced parallel thin traces, a flatbed scanner or good quality digital camera macro-shot can produce a hard-copy printout or on-screen image, magnified.
A sharpie (fine-point marker) can be drawn over a track being traced, but leave solder-pads unmarked.
Vias, or through-holes that link top and bottom traces, can be used as reference points by temporarily feeding a thin solid hookup wire through to opposite side.
For more than one 'reference wire', use different-colored permanent marker per wire.
Other drilled holes can be used the same way.
For through-hole component leads/pins, count or measure distance and angle to next pad on net (track).
This is easier when known patterns are identifiable (DIL components, transistors, transformers...).
Things you will probably need:
Magnifying glass.
Directional source (torch, desklamp) for those dark corners between components.
Light box or LED floodlight, to shine through the board substrate.
Colored markers.
Thin solid hookup wire, stripped.
Flatbed scanner or camera (optional).
Component & schematic-drawing basic skills.
A lightbox below the PCB can assist in seeing the opposite side's 'mask-shadow' of traces, but SMD or large comopnents may block some tracks.
A ruler or vernier can be used from edge of board, or known holes /cutouts.
Remember, when board is flipped, the 'image' layout is also inverted, either vertically or horizontally.
Where a PCB has lots of closely-spaced parallel thin traces, a flatbed scanner or good quality digital camera macro-shot can produce a hard-copy printout or on-screen image, magnified.
A sharpie (fine-point marker) can be drawn over a track being traced, but leave solder-pads unmarked.
Vias, or through-holes that link top and bottom traces, can be used as reference points by temporarily feeding a thin solid hookup wire through to opposite side.
For more than one 'reference wire', use different-colored permanent marker per wire.
Other drilled holes can be used the same way.
For through-hole component leads/pins, count or measure distance and angle to next pad on net (track).
This is easier when known patterns are identifiable (DIL components, transistors, transformers...).
Things you will probably need:
Magnifying glass.
Directional source (torch, desklamp) for those dark corners between components.
Light box or LED floodlight, to shine through the board substrate.
Colored markers.
Thin solid hookup wire, stripped.
Flatbed scanner or camera (optional).
Component & schematic-drawing basic skills.
