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

Jeff C

Jeff C

Active member
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!
855EE297-D464-47F8-880D-F0D8B9C40E15.jpeg 15E06C0D-93DB-4AE9-944D-BA1BED3416FB.jpeg
 
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well, hard to tell. I'm just strumming a bit and if I hear audio, I'm concluding it's working. I'm stumped by the in and out pads on the PCB, though. I wired the switch as instructed, I get audio from the in and out lugs on the switch, but only audio on the out pad on the PCB. Nada from the in pad.
 
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if you are late to the thread, I'm not using the switch with the daughterboard in the pics above. I replaced that with a regular switch with solder lugs.
 
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You mean there is no signal going from the input jack to the in pad on the PCB? If so, how are you getting signal downstream?

If you own a looper pedal, I suggest recording a loop, then plugging the pedal to the looper output so you don’t have to keep strumming. It makes debugging a breeze (using a signal generator would be another option).
 
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After watching this thread for a while I want to say 2 things. First and foremost I hope you get this working soon. Troubleshooting is THE most frustrating part of the build process and your patience will be rewarded.

Secondly, I'm watching and I hope you're realizing that amongst all this frustration you are learning. Once you find out what went wrong with this build I can almost guarantee you won't do it again. Many people here are doing a great job trying to help you out and I hope someday you will pass it on to the next noob in need.
 
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Jeff C said:
Ok, brain fart here. Yes, I get sound from the in pad, not the out pad. 🤪
Click to expand...
Just to go back to @giovanni checkpoints...:

  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
Make sure you use these points to check for signals.

1652201679530.png

@giovanni , you might want to double check my points... hopefully I didn't make a mistake.
 
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Jeff C said:
Ok, brain fart here. Yes, I get sound from the in pad, not the out pad. 🤪
Click to expand...
On that note, be sure you pay attention on your testing process.

1- Always check your inpad before checking any other points, this will confirm your switch is engage and sending a signal to the board.
2- Every time you check a point, remember that if you check on the back side everything is revers. So when ever possible check your audio patch facing the components, it will limit your chance of forgetting to reverse.
3- If you hit a point with no audio where expected, always go back to check your inpad to make sure nothing has disconnected. Then recheck you dead point for confirmation.

Think based on your last pic, you are currently using a white wire for your inpad and black for your outpad and they are soldered from the top so when checking for your input confirmation, make sure you align to your white wire...
 
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Yep. Got it. Today is weird. I did put a better point on my probe. But now, I only get the in pad, r1, c1, r2 and q1 only. None of the others I listed yesterday give a signal, including the IC.
 
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Jeff C said:
No audio there but I will check again…….after I mow the lawn……..
Click to expand...
Nada from r6 or q3. Does r6 feed q3? If so, does that mean I should replace that resistor? The q1-4 are all J201’s which I understand are hard to find or of iffy quality. But if the r6 isn’t sounding, should start there?
 
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giovanni said:
Don’t replace anything yet. It may be the transistor but it may be any component setting its bias. Gotta take another look at the schematic…
Click to expand...
I have to admit that this schematic puzzling me...

I had understood the first part to be the yellow audio path, but the blue part is what throws me way off...

1652219964837.png

However, it looks like Q3 is inverted... that confuses me even more !
 
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