Pedal Tracing for Noobs

[Adam_DIY]

So I've borrowed an overdrive pedal from a friend of mine and I'd like to have a go at tracing it for a laugh.  It's all through hole components and I can read the capacitor values/transistors etc because they haven't tried to hide any of that.  How do I go about starting to trace it?  It might be beyond my skills at the minute but I'd like to have a go for shits and giggles 

[jkokura]

There's a few methods, and others here are much better at it than I am, but often you'll need to be able to remove it from the enclosure, and take a look at both sides.

The best method I've seen is when you take pictures of both sides of the PCB, then overlay them over each other so you can see all the traces line up with the parts. You have to invert one image I think, but this allows you to go in with a paint program and colour code the traces. Then you can 'trace' the circuit through, labeling parts as you go.

When I tried it myself, I used to use paper and a pencil, but I think if I did it now I'd be using Eagle to do the schem right away. I'm much more comfortable with a digital schematic.

Jacob

[flanagan0718]

This is something I've wanted to do With a Nady TD-1. I am lacking in the skills to do so. I haven't spent much time on it but there might be a couple of youtube tutorials or something. Let us know what you find!

[Adam_DIY]

There's a few methods, and others here are much better at it than I am, but often you'll need to be able to remove it from the enclosure, and take a look at both sides.

The best method I've seen is when you take pictures of both sides of the PCB, then overlay them over each other so you can see all the traces line up with the parts. You have to invert one image I think, but this allows you to go in with a paint program and colour code the traces. Then you can 'trace' the circuit through, labeling parts as you go.

When I tried it myself, I used to use paper and a pencil, but I think if I did it now I'd be using Eagle to do the schem right away. I'm much more comfortable with a digital schematic.

Jacob

Thanks Jacob the pedal has board mounted pots so will be pretty easy to get out of the enclosure.  I'll have a look at the weekend and see how I get on.  I have a suspicion as to what circuit its based on having looked at the parts used but it would be nice to do it properly.  Worst case scenario I'll take some pics note down all the values used and come back to it when my knowledge has increased again 

[galaxiex]

I have been tracing old, obscure, cheap, Japanese (and other) guitar amp circuit boards for some time now.

Some examples of my work can be seen at.... http://www.ssguitar.com/index.php

But you have to register (free) to see the pictures. Same user name.

This only works for single sided boards. Double sided (or more) would be difficult. 

My method is to remove the circuit board from chassis, (AFTER making/drawing a map of where all the wires go!)
Also take pictures BEFORE you de-solder/cut any wires to remove the board.

Once the board is out I scan the copper trace side and import the pic to a drawing program. (I use paint.net)
Any program that has layers will work.

Then the fun begins....
Start by creating a new layer and draw (copy) the traces on your new layer.
I use new layers for each type of component. Resistors, Caps, Transistors, etc.
Color coding also helps.
eg, I make all caps yellow, just draw a simple yellow line for each cap from trace to trace where it is located.
Continue on with the rest of the components (colors) and layers.

Then I go in and (new layer) add the component values and designators (C1, R6 etc...)

Once its all traced out, this is called a board layout.
From the layout I work thru it to create a schematic.
I use the free program ExpressSCH.

This is probably a lot more complicated than tracing a pedal.... or... maybe not....

Anyways.... hope it gives you some ideas. 

Couple examples....

Edit;
Oh ya... if its a really simple circuit you can hold the board up to a strong light, looking from the component side,
ans "see" the traces through the board.
A light table works really well for this too.
Just draw from that.

[Lubdar]

I've been working on tracing pedals for about a year now.  I've still got a lot to learn but I thought I'd offer what i've learned thus far.  The photo approach works out pretty well, but for me I need to hold the PCB and tilt it with my eye real close!  Getting a good look at the PCB and where the traces are can be the most painful part. 

I typically draw out everything that I can on paper, I eyeball it to scale with all the components and then use red and blue pens for the top and bottom sides of the pcb.

Take breaks, even when you think you're finished, try going back from the start and see if you get the same thing.

Holding the PCB up next to a lamp help with viewing traces. The hardest part can be if an 16 pin IC is covering the traces.  In that case I usually check the continuity of pads with a multi-meter.

Depending on what you're working on you'll most likely come across some common topologies, when drawing out the schematic, you may not always be able to see them, but after you've become more familiar with typical topologies it'll be easier

Best of luck.  To me this is just like a different sort of puzzle.
Lubdar