Tracing a PCB schematic for a repair

[dmp]

Recently tried this and it worked pretty well. I did it in powerpoint.

- take a picture of both sides
- flip one of the pictures vertically (mirror)
- overlay the images and make the top image transparent (adjusting the transparency as you trace out the schematic is helpful)
- adjust the height & width slightly as needed so the components line up with the pads

Easier to trace out the schematic

 

[mrclunk]

Great idea.!
Sticking a led inspection lamp or lightbox underneath the board so u can see thru can be handy too.

 

[JohnRoberts]

Nice, where was this technology decades ago?

Fun is tracing out hidden traces inside multi layer boards, even more fun trying to fix one (hint you can often drill out vias to open a buried trace. )

JR

 

[dmp]

Sticking a led inspection lamp or lightbox underneath the board so u can see thru can be handy too.

Yes, and some amount of board in hand is needed to get component values, but I have a much easier time tracing it out looking at a picture like this than holding it in hand. Goes faster for me, but for each their own

Nice, where was this technology decades ago?

My dad had a B&W darkroom I got to experiment in growing up. It was fun but getting two pictures developed like this wouldn't have been worth the effort - haha.

Fun is tracing out hidden traces inside multi layer boards

Hopefully you'd be able to get a schematic of a modern board. Hidden traces would be a nightmare.
In this recent case for me, (roland synthesizer) the only schematic online was the first version. Second version changed the chorus to different chips (SAD512D -> MN3004), so Roland redid this whole board basically. It was helpful having the first version of the schematic to 'revise'
You can see the wires hanging off where I rigged a pre-chorus insert. Works great and this project is done for me now.

Thinking about this makes me wonder if there is automated software now to derive schematics, similar to how a compiled executable can be 'uncompiled' to source code, for reverse engineering. I expect businesses do this: buy a competitors product and try to learn everything about it they can. After a web search it seems if you create the layout, using images like this, there are software tools that can make the schematic.

 

[JohnRoberts]

Thinking about this makes me wonder if there is automated software now to derive schematics, similar to how a compiled executable can be 'uncompiled' to source code, for reverse engineering. I expect businesses do this: buy a competitors product and try to learn everything about it they can. After a web search it seems if you create the layout, using images like this, there are software tools that can make the schematic.

In theory if you had full cad-cam data for fabricating and assembling a PCB, the information exists to work backwards to a netlist and by extrapolation a schematic. It might not look like a human drawn schematic.

Think about who would use such a tool... knock off artists? Would they pay to develop one?

I recall last century sitting in the Hong Kong office of a huge Chinese contract manufacturer and OEM. The executive I was meeting with bragged about having 100 DSP engineers working in a lab in mainland china that could reverse engineer any DSP SKU he wanted. He may be exaggerating but only some. I think he mentioned reverse engineering an advanced dolby theater encoding standard.

JR

 

[dmp]

Think about who would use such a tool...

Probably not audio gear since most everything is already a copy from a old schematic and new IP is worth less than marketing & cheapening manufacturing.

But in something like EVs that have multiple custom ECUs and a huge ongoing technology race I could see competitors buying a vehicle and completely deconstructing it to learn, for one example