reverse engineering pcb for schematics

[ant17]

hi i think anyone thats ever tried repair a electronic equipment knows the pain of trying to find a schematic but having no luck after hours of net searching and then findind you may have reverse engineer a board. from the physical board to a schematic does anybody have any methods they use to reverseengineer a a board for schematic

[james_s]

I use a variety of methods depending on the complexity and layout style. Usually I start with a high resolution photo or scan of both sides of the board, then flip one so it's easy to visualize where everything is on one side while looking at the other then print them out on full pages. Then pick a starting point, often ground is an easy one, draw a wire for that with a pencil on a piece of paper and then sketch the symbol for each part connected to that node. Mark off the traces and joints on the printout of the PCB as you go along to keep track of what you have covered. Then look over your rough schematic and start moving parts around as needed for it to make sense, for example you might realize that four diodes scattered around actually form a bridge rectifier in which case you'd want to rearrange them them as such in the drawing. Once you're fairly sure you have the correct circuit, re-draw it on a new sheet in a more tidy arrangement, or you might use PCB CAD software to make a proper schematic in that.

[fzabkar]

Likewise, I use CCD scans (not CIS) of both sides. Then I mirror one side and move it around until the cursor sits at the same reference point on the top and bottom sides. Then you can flip between windows in your image editor as you move the cursor to a different location.

[ant17]

thanks for your reply guys just a couple questions is the idea to draw on the photo or use it as refrence and what is meant by CCD could please clarify thanks

[fzabkar]

https://www.tavco.net/wide-format-plotter-scanner-blog/bid/107329/compare-ccd-vs-cis-scanner-technologies

[james_s]

I draw on the photo with a physical pen on a a printed image on paper but you can do whatever works for you. The important part is keeping track of all of the nodes and what you have drawn in the schematic.

[ant17]

so basically just print the photos  and draw components directly on them the components directly is it ever done somthing like orcad

[james_s]

You can do it directly into CAD if you want, like I said, it's up to you, do whatever you find works. Reverse engineering is a niche thing, it's a bit of an art. Unless you have an amazingly good memory you're going to need some way to keep track of what traces and components you've translated into schematic so you don't miss anything. I find that paper and a pencil work well for me, but there's no reason you couldn't do it entirely in the digital realm.

[amyk]

Go to YouTube, search for "bigclivedotcom with schematic"...

[SMdude]

I use diptrace. You'll need an older version(2.xxxx) though as the new version doesn't import pictures nicely that I can see.
You can import a photo of the board into the schematic editor, then drop all your components in place. You have to do top and bottom in a separate area so it doesn't overlap and get messy.
Then just link the components, I'll generally solder a wire onto a node and then test around with the multimeter in continuity mode and link everything that beeps.

Then once you think you have everything complete, begin unscrambling and putting the components together so they make sense.

[asis]

Hi everyone,

I, in general, have been doing this for a long time.
And I came across a fairly universal SW Visio-5 for that period (then still Visio Corp. ~ 1996).
 https://en.wikipedia.org/wiki/Visio_Corporation     
Then came the release of Visio-10, and then, Microsoft made it an Office application.
Visio originally had a Stensil's set with radio components and other very useful things.
Visio has a built-in MASTER for creating your own base of almost any component's.
Everything mentioned can be implemented in Visio, including placing a PCB photo as a background and drawing component relationships on top of it.
The only thing I don't like now is that the design has changed.
It has become oversaturated with different options and starts to get very annoying. It seems to me that Indian programmers have overdone it.
Best the enemy of the good.

As an example, the PSU Delta circuit.

[David Hess]

I use a variety of methods depending on the complexity and layout style. Usually I start with a high resolution photo or scan of both sides of the board, then flip one so it's easy to visualize where everything is on one side while looking at the other then print them out on full pages.

That is how I do it.  A flatbed scanner or good camera can be used.

[ant17]

thanks guys you have helped me alot

[jerryk]

There are plenty of photo rendering programs that allow you to overlay two images and adjust the transparency so that you can see both sides at once.  Photoshop was used here but there are many others that support layers etc.

Jerry

[asis]

Visio also works with layers.
It is also possible, at the stage of creating a diagram of connections between components, to effectively use dynamic connections.
To automate the process, you can use macros that link the base of logical representations of components with the base of their real package layout (DIP, SOP, PLCC, etc.).
All mechanisms in Visio are there, you just need to master them.

[archil]

it is hard work, reverse engineering any pcb. 

[teksturi]

It will help that you find reference design for IC's. You will also understand design better. You can also find "bugs" in design because not all designers use reference designs and they get something little bit wrong. They may not be huge "bugs" but example wrong decoupling capacitors or some pin is left floating.

One way is to use xray but that usually is little bit pro side off reverse engineering.