Thursday, 16 February 2017

A brief guide into tracing out a PCB to convert to schematic. b3k Clone

I haven't posted on here in a while. This is my little guide to tracing out a PCB.
I ordered a GUMA drive kit from Schalltechnik_04 which is a Darkglass b3k clone and before I assembled it I'd thought I'd give it a go tracing it out to produce a schematic. If you do want to build this pedal I highly recommend buying this kit. It's a very well laid out kit.
First thing I needed to do was get some super fine pointed tips for my multimeter. I ordered these from Aliexpress. The multimeter I have used for this is a APPA 62 and I've just used it on the continuity function.
Fine pointed tips

I took a high quality photo of the PCB on my Sony xperia z3 and printed out a bunch of copies of it to help with the tracing.
High quality photo.
I started to trace out the circuit with my multimeter. I removed the unnecessary parts that I didn't need to trace and blacked them out on my printed photos. The jacks and relay bypass was not needed to be traced. I started in a logical order starting with the power section. As I found connections I would draw them onto 1 printed age and cross out the component on another printed page I would also draw the schematic onto another piece of paper. After doing all the power stages I then went to the input and worked my way through the whole PCB. This whole process took me 20+ hours.

The tedious task of tracing

Darkglass B3K Schematic. Updated 20/2/2017
After I had my completed paper schematic I then drew it up in EAGLE CAD. Any CAD package is fine I'm just familiar with EAGLE.

PCB I have drawn up.
This Schematic is verified. PCBs turned out great. Have since redesigned this layout to fit into a 1590B and also have the ability to make the b3k and vmt.

Update 18/2/2017

Got around to building the kitset I based my trace on. My work it's a good overdrive

Guts shot

Vashta Nerada - The Shadows That Melt The Flesh

Update 20/2/2017
Updated the drawing as I had misplaced a resistor. R22 moved from above diode to between supply and pin 1 on the 4049.

Update 7/3/2018
I have made this effect quite a few times now. Schematic is verified. I've since made a new PCB that fits into a 1590B and can do the b3k and vmt by just swapping a few components out. I'm starting to make my own modifications on the circuit too.


  1. So there is a error on this schematic. I will update and verify once my PCBs get in.

  2. Hi Tony Pepers,

    Did you make your own pcb or you use the one you bought from schalltechnik? Have you applied your mod (tone stack)?


  3. Did you ever get the schematic updated?

    1. Yes. The schematic in above is good.

    2. Nice. I am trying to find your relay in that schematic. Is that what is in the upper left? Also, what's your thoughts on using a P-Channel MOSFET on the incoming power line for reverse polarity protection instead of diodes? That way if it's reverse polarity, it just doesn't function and it won't blow up anything, however, if the power polarity is correct, you only lose a little heat (assuming RdsON is a low value).

    3. Hi Eric. I removed the relay bypass and decided to go with the 3PDT style bypass.
      Yeah I have seen the P-Channel MOSFET polarity protection. I generally just use a 1N5817 diode in series, low cost 1 part.

      Hey if you ever want a PCB for this flick me an email

  4. Please share me ur email. Im interested.

  5. Hello there, I am interested in PCB, could You mail me?


  6. Hey, any chance to get your eagle files (pcb/schema)?

  7. I have a problem with the circuit (I build it). When I open the drive knob past 95%, I get an oscillation. I measured with a oscilloscope and found that the TL072 IC2B seems to have an oscillation feedback loop. I read of more people having this issue. Do you know what would cause this and how to fix?

  8. Hello! Great work. May i have your PCB design please? I would appreciate that.