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!

 

[Jeff C]

And I just now noticed that the IC gets very hot.

 

[Jeff C]

C100 a little warm too.

 

[Mcknib]

Sounds like a dead short +9v connected directly to ground drawing a current check around the power pads

Check you don't have continuity on the DC jack lugs ie they're not connected check with no power to the circuit

Check C100 doesn't have continuity across it check IC pins 7 and 4 don't have continuity and all the VCC points on the schematic don't have continuity to ground

 

[Jeff C]

C100 a little warm too.

Actually the IC only heats up fast when I put the bridge in between the anode/cathode on the protective diode.

 

[Jeff C]

No connectivity between the dc jack lugs or their respective pads on the PCB.

 

[Jeff C]

C100 does not have continuity across it.

 

[Jeff C]

Ic pins 4-7 have no continuity.

 

[Jeff C]

By VCC points, do you mean the first points the line from the VCC hits on the schematic?

 

[Jeff C]

By VCC points, do you mean the first points the line from the VCC hits on the schematic?

Weird, one side of the R4 doesnt beep when connected to ground but reads 188 on the multimeter….

 

[Mcknib]

Yes you'll see VCC labels on the schematic top of R2 etc you don't want continuity to ground on any of them place a probe on ground the other on the VCC point

You're basically looking at power points to try and find where it shorts

Also meant to say continuity check your + and - power pads

Finding a short isn't easy so it's checking obvious possibilities

Have a look for bridges on the solder side under magnification remove the jumper from D100

 

[Jeff C]

Getting continuity between r6 and ground

 

[Jeff C]

But I guess that makes sense from the schematic

 

[Jeff C]

No continuity between ground and any of the Q’s.

 

[Jeff C]

There is no continuity between the + and - power pads. Took the jumper off as soon as the IC started heating up. The only bridge I can see on the solder side is one I put in between r6 and q1 per a previous posting.

 

[Mcknib]

Sure does that's not directly connected to VCC just check each point labelled VCC to ground only

I'm saying dead short because you say the IC and C100 get hot so it's drawing more current than it should

But from what you described earlier 9v one side and 1.2v the other side of D100 that'd be a short circuit

 

[Jeff C]

Sure does that's not directly connected to VCC just check each point labelled VCC to ground only

I'm saying dead short because you say the IC and C100 get hot so it's drawing more current than it should

But from what you described earlier 9v one side and 1.2v the other side of D100 that'd be a short circuit

So, it’s correct that there’s no continuity between the + and - pads, right? Also, none of the vcc points, I.e. the Q’s, show connectivity to ground. Only the r4 seems to read 188 but no beep. Here’s a new pic of the solder side. Ugly, I know.

 

[Mcknib]

I've just realised I should have told you to snip one side of D100 before jumpering it I was going on the path of least resistance but maybe it being soldered to the board it hasn't bypassed it

What I'd do is snip D100 out completely on the component side of the pcb and solder a jumper in place leave as much of its pins as you can then solder on a jumper wire

Before you do that continuity check the + power pad to D100 anode pin and cathode pin to R101 probe the actual diode pins just as a quick check to see if D100 solder pads are good

 

[giovanni]

A short is likely but it is also possible that you have an incorrect resistor value. Something like a 100R instead of a 100K could do that. Did you check all component values? And by that I mean check the color bands on all resistors and verify they are correct?

 

[Jeff C]

So, it’s correct that there’s no continuity between the + and - pads, right? Also, none of the vcc points, I.e. the Q’s, show connectivity to ground. Only the r4 seems to read 188 but no beep. Here’s a new pic of the solder side. Ugly, I know.
View attachment 26641

Should there not be continuity between the + power and r4? I don’t read any, but it seems from the schematic that it should.

 

[Jeff C]

A short is likely but it is also possible that you have an incorrect resistor value. Something like a 100R instead of a 100K could do that. Did you check all component values? And by that I mean check the color bands on all resistors and verify they are correct?

Yes. No wait, R2 could be wrong. Checking the others, this will take a long time….. No, r2 is good. Damn bands are hard to read.