The voltages you are wondering about are simple actually. The Power and Switching schematic shows the incoming voltage of 9 volts and VC which is that same 9 volts but protected by D5 and filtered by C27 and C28. Actually VC is the voltage of whatever you are providing as the power source, whether a battery or adapter. The Fuzz schematic shows using that same VC and injecting it into the circuit between resistors R16 and R18. The Overdrive schematic shows that same VC and using it create VB1, over to the right side of the page. VB1 is the result of the voltage divider created by R13 and R14. Then VB1 is used throughout the Overdrive and measurable with your DMM at the points shown. That voltage divider having equal value resistors should yield exactly half of VC, presumably near 4.5 volts. The Tremolo introduces us to VD. VD will be a very very slightly reduced VC after passing through R37. So 9 volts and 4.5 volts (half of 9 volts) is what this board works with. Should troubleshooting become necessary because of how something behaves, other measurements according to expectations may then become necessary. Nothing to fret yet and hopefully not at all.

Welcome Henri. I can’t blame you wanting to get this working. It’s fantastic. You should go ahead and take it apart and fix any backward or blown leds. You are going to need to take the time to reflow all the switch and pot joints. Many look like cold joints that were soldered in haste. You will likely benefit from reflowing the rest of the board as well. As you do, remove the IC first and be super careful around and at the transistors so as not to cook them. Your soldering should result in a lot of shiny mounds shaped more like a hersheys kiss. Barry has a soldering video here someplace. I couldn’t find it just now. Take a look at the Guides Page, though, and scroll down to the guides below near the bottom. Read them all. Good info in there. How did it turn out matching your components up with the examples Jeff24 gave? All good there?

I would suggest using some liquid solder FLUX when reflowing along with your solder.

There are many cold solder joints. Also be careful of the iron temperature.

Finally be sure you are using a fine conical tip when doing the small pads above the switch as some of them look like cold joints or limited solder.

For the larger switch pads place a small drop of flux on each pad and reflow the solder. You will not be able to force the switch in any closer but as long as you make a good solder connection you will be fine.

I always apply FLUX to switch lugs before soldering them to PCBs. It just makes everything better.

Most importantly, take your time, and be careful not to burn any solder pads or you will likely need a new PCB.

Glad you got it working. That should be a relief just in time for the holidays. According to your post details the problem with the led is that it is the wrong type. There are Common Anode led’s and Common Cathode led’s for bi-color of RGB led’s. All of Barry’s boards need a common anode bi-color led. It’s all about polarity of the longest leg. I believe you have installed a common cathode led. Thats why if you reverse the polarity the led works with both colors. You need to replace it with the correct type. Common Anode is what you seek. Have a great holiday.