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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Power supply plug tests at 9. I tested the jack it plugs into, at the lugs. with no wires attached, I get 9v. So, there doesn't seem to be a short in the jack. But when I attach the wires to the jack and test it at the same lugs, it drops to 1.2.
 
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Jeff C said:
Power supply plug tests at 9. I tested the jack it plugs into, at the lugs. with no wires attached, I get 9v. So, there doesn't seem to be a short in the jack. But when I attach the wires to the jack and test it at the same lugs, it drops to 1.2.
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Tricky tricky. It sounds like you have such a large voltage drop that the power supply can’t keep up. Are any resistors overheating?
 
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I took the bypass bridge I made off of the D100 protective diode and I'm back to 9v on one side and 0 on the other. Does that not tell me my diode is busted and should be replaced?
 
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You could run a 9v wire to the + side of C100 just to test it

It doesn't look like you've got power wired to a DC jack?

So tack solder a wire to C100 + on the underside and use that as your 9v wire you'd then be bypassing D100 without having to remove anything
 
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well, not sure what you mean. I have 9v coming from the power supply to the jack. I soldered the wire to the jack. I get 9v to one side of the diode, 0 on the other side (just as I had when I just had the wire hooked on the jack). I’ll try the bypass to the C100……Tks!
 
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He means getting 9V directly to the side of the diode where you get 0V. The diode is just for protection so bypassing it will at least tell us if the pedal is working. I would avoid soldering/desoldering stuff at this point and use alligator clips instead. We don’t want to damage things that may not be broken.
 
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So, I connected a wire from the power jack to C100 and get 9.23v! I’m assuming the protective diode is at least part of the problem. To test the rest, I’m going to need to solder that bypass wire because I can’t get an alligator clip on it and if I could it would likely slip off as I mess with the rest…….
 
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Well, dang. I mistakenly connected to C20 the first time (#231 above), and was sooooo happy. But when I soldered, I soldered it correctly to C100 but get………only 1.2v there. And of course no audio on Q1 drain. Does this mean C100 could be bad too?
 
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I think it means neither the diode nor C100 are bad and there is something else shorting out. C20 is directly connected to the op amp output so I’m not sure how that would give you a 9V read anywhere than at that pin…
 
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From your first pics I didn't see a DC jack but I can see in your later pic you're using one

All you're trying to do is feed 9v to the + side of C100 to see if D100 is a problem by bypassing it

Get a piece of wire tin both ends with solder and simply tack solder it on the underside one end to the + power pad the other to C100 + pad

Just hold the wire on the solder joint and melt the solder already on it tacking it to the joint

If you only get 1.2v on D100 cathode you won't get VCC or VREF bias voltage once you install your jumper check what voltage you get both sides of R101

20220522_224756_copy_432x422.jpg
 
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Mcknib said:
From your first pics I didn't see a DC jack but I can see in your later pic you're using one

All you're trying to do is feed 9v to the + side of C100 to see if D100 is a problem by bypassing it

Get a piece of wire tin both ends with solder and simply tack solder it on the underside one end to the + power pad the other to C100 + pad

Just hold the wire on the solder joint and melt the solder already on it tacking it to the joint

If you only get 1.2v on D100 cathode you won't get VCC or VREF bias voltage once you install your jumper check what voltage you get both sides of R101

View attachment 26609
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I did that (well, I connected to the positive side of the dc jack instead of the PCB pad) but once soldered, it only showed 1.2c at C100. Prior to soldering it to C100, the loose end read 9v.
 
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Maybe time for a recap I'm getting a wee bit confused reading through it

As far as I understood it you got 9v to the pcb + and - power pads and to the anode of D100 and little to nothing at D100 cathode?

Now as far as I can make out you get 9v on the DC jack lugs until you wire it to the pcb power pads then it drops to 1.2v is that correct
 
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