SOLVED Cobalt Drive problems…..SOLVED……..FINALLY!

[Jeff C]

New member here and also new to building pedals, as you will shortly see. I previously built a BYOC Reverb pedal kit successfully and it sounds great. I’ve also built from scratch a Strat, a Tele, a 59 LP, and an LP Junior. So, I wanted a blues driver pedal and thought I’d take a whack at the Cobalt Drive from PedalPCB. The directions are not as detailed as in a kit so I’ve had some difficulty. Clearly in over my head. I managed to procure the parts from the list (not without trial and error on my part) from Tayda. I mistakenly bought a switch without solder lugs so after consulting a patient, helpful friend, bought a daughter board and did my best to figure out how to marry the two - having no skills whatsoever in electronics. History major. I have managed to assemble it but I get nothing from it except static pops when I plug it in. Bypass doesn’t work. No idea what I’ve done wrong but I suspect it revolves around needing to do more with the daughter board on the switch. But what do I know? Here’s a couple of pics (the power jack is not there but I did connect it to test). And I haven’t installed the LED yet. Any and all suggestions are eagerly welcomed. You may recomemd I should just start over but I hope not….. Thank you!

 

[EGRENIER]

So, best I can tell is the only signal I got is on C19, D5 and 6, and R20-23

The only way I can imagine this happening is if you're feeding the input to the out pad....

 

[Jeff C]

Ok, I think I’m tracing this path now, Stand by…….

 

[EGRENIER]

Wait, no sorry, I do have connectivity to one side only of the r1 and c1 from the in pad

OK that makes sense, but you should get a tone if you have connectivity on C1 or the one side of R1... if you don't then it looks like you have connected the signal to the out pad... see my other message.

 

[Jeff C]

Wait, the connectivity to r1 is from the out pad…….

 

[Jeff C]

Scratch that, I keep flipping this thing over and seeing it backwards

 

[EGRENIER]

Wait, the connectivity to r1 is from the out pad…….

If not mistaken you should get connectivity of the green dots (C1 and R1) to In pad and connectivity of Red dot (R1) to ground. Not quite sure which side of C1 is the entry point...

 

[Jeff C]

So, as of now, using the multimeter, I’m getting connectivity from in to r1 and from r1 to both c4 and r7, from c4 to r8, from r8 to q3 and q3 to r6………

 

[Jeff C]

And with the audio probe, gettin signal from the out pad on the PCB and the other points noted above.

 

[Jeff C]

Plus c17

 

[EGRENIER]

And with the audio probe, gettin signal from the out pad on the PCB and the other points noted above.

Is bypass working now ? Did you probe with the switch engaged ?

 

[Jeff C]

If not mistaken you should get connectivity of the green dots (C1 and R1) to In pad and connectivity of Red dot (R1) to ground. Not quite sure which side of C1 is the entry point...

View attachment 26111

Yes, I have those

 

[EGRENIER]

Yes, I have those

Then if you have those you should have audio on the In pad, audio on C1 (both side), audio on the middle pin of Q1 and middle pin of Q3.

 

[Jeff C]

Is bypass working now ? Did you probe with the switch engaged ?

Yes, bypass works.

 

[Jeff C]

The only way I can imagine this happening is if you're feeding the input to the out pad....

Well, I have it wired as shown in the PedalPAB doc, but yes, I get sound only from the out pad, which is weird. No signal from the in pad, or from the switch lugs for in.

 

[giovanni]

This pedal has a ton of components. If you are using an audio probe, I would start from the transistors. If any of the following fails, you found the problem, no need to continue:

1. Check if you have signal at the gate of Q1
2. Check if you have signal at the gate of Q3
3. Check if you have signal at the drain of Q1
4. Check if you have signal at the base of Q5
5. Check if you have signal at the collector of Q5
6. Check if you have signal at the gate of Q2
7. Check if you have signal at the gate of Q4
8. Check if you have signal at the drain of Q2
9. Check if you have signal at the base of Q6
10. Check if you have signal at the collector of Q6
11. Check if you have signal at pin 3 of the IC
12. Check if you have signal at pin 6 of the IC

For reference, the J201, 2N3906 and TL071 pinouts are as follows:

 

[Jeff C]

Getting signal from emitter and base on Q7. NO signal from all the other Q’s. I have signal from pins 3 and 6 on the IC.

 

[Jeff C]

Gonna quit for today. The voyage of discovery resumes tomorrow…….

 

[giovanni]

Sorry I don’t see how you can get signal at the IC if there is no signal before. How are you measuring the signal?

 

[Jeff C]

with my audio probe. strum the guitar, sound comes from the amp.

 

[Jeff C]

getting audio from C17 and 19, D5 and 6, and R20-23. Plus the two IC pins.