comradehoser
Well-known member
Hello dear internet peoples.
I come to you with the case of the Sabbath Distortion. Here be pics and schematic. Presence of flux is from reflowing.
A little background: this is around my 16th pedal, and my first (kinda) unsuccessful pedalPCB build. Have built Parentheses, Arkaim, Plecostomus, Death Cap, Pyrocumulus, Bayonet, and Byzantium with exactly 0 issues and 100% heavy fuzztastic joy. (and on a side note, my forum membership is not my store membership? Was trying to leave reviews with my forum ID, but am not recognized).
I am maybe at a novice high level in my electronics learnings? I know just enough to color by numbers and solder inside the lines. I kind of get what the various bits do, but not enough to create happy trees by myself. The mysteries of component selection and arrangement elude me.
So... This pedal, unlike the others, did not fire up. Have bypass, have LED. Started moving stuff around, and I put my finger on three leads of one of the transistors, Q6, I think. Little bump and the pedal starts up. Great, I play the pedal, and hello, it's Iommi in Paranoid, it's Iommi in Into the Void, it's nice to Iommi for a while. I unplug it, mess about with the Byzantium flanger, but when I get back to finding Iommi again, nothing. Fiddle around a bit with the transistors, jiggle Q4 this time, and it bumps and fires up again. The unplug, jiggle, and bump cycle repeats centered around Q4, no other Qs will do for Iommi. I figure maybe the solder joints in the sockets are dicey, so I reflow everything in Q4 (and 5 for good measure), but now: no Iommi! Not for love or money. So now I go try to find where my good friend Tony is hanging out. I should mention that I used PF4393s by Central Semiconductor from Mouser, which you can find here. Otherwise, I try to follow the BOM religiously. When or why to choose MLCC vs. box caps for a given value when unspecified is another question I have, but maybe that's a separate thread.
Enter audio probe: Tony is (very) loud and proud along the whole component chain until Q4, where the signal distinctly dies and does not continue. I recheck and reflow everything in that section attached to Q4 (C12, C13, R16-20, and Q5). Nothing.
Switched the PF4393 transistors around in the sockets, all transistors give signal in Q2 and Q3 positions where there is signal, so I can't blame a faulty component.
I check continuity between transistor pins and solder joint, sockets and solder joints, and between sockets. Continuity checks out--I don't see anything that looks like a solder bridge even though there are some fat solder balloons on the component side of Q4 socket pins, but they don't appear to be touching. There also seems to be continuity between the sockets and C12/R16 and the sockets and R20/C13, although they just post dwindling value and never the beep (capacitors, am I right?).
Maybe it's a ground or voltage supply issue to Q4, I think to myself. Enter voltage probe: C12 and R16 show 6.18v prior to Q4. Q4, R20, and C13 read zeros or close to it.
Here are the rest of the numbers:
V in: 9.438
Transistors, reading Gate, Source, Drain (or pins left to right with the flats facing away from you)
Q1: 1.53, 2.12, 5.965
Q2: 0, 1.219, 5.022
Q3: 4.14, 6.822, 9.215
Q4: -0.243, 0, 0
Q5: 4.405, 6.184. 9.215
Q6: 4.188, 5.735, 9.215
Don't really know what to do besides maybe pull and reinstall another socket at Q4? Or maybe there is an issue with the voltage supply values?
Cheers, and you have what appears to be a lovely forum.
I come to you with the case of the Sabbath Distortion. Here be pics and schematic. Presence of flux is from reflowing.
A little background: this is around my 16th pedal, and my first (kinda) unsuccessful pedalPCB build. Have built Parentheses, Arkaim, Plecostomus, Death Cap, Pyrocumulus, Bayonet, and Byzantium with exactly 0 issues and 100% heavy fuzztastic joy. (and on a side note, my forum membership is not my store membership? Was trying to leave reviews with my forum ID, but am not recognized).
I am maybe at a novice high level in my electronics learnings? I know just enough to color by numbers and solder inside the lines. I kind of get what the various bits do, but not enough to create happy trees by myself. The mysteries of component selection and arrangement elude me.
So... This pedal, unlike the others, did not fire up. Have bypass, have LED. Started moving stuff around, and I put my finger on three leads of one of the transistors, Q6, I think. Little bump and the pedal starts up. Great, I play the pedal, and hello, it's Iommi in Paranoid, it's Iommi in Into the Void, it's nice to Iommi for a while. I unplug it, mess about with the Byzantium flanger, but when I get back to finding Iommi again, nothing. Fiddle around a bit with the transistors, jiggle Q4 this time, and it bumps and fires up again. The unplug, jiggle, and bump cycle repeats centered around Q4, no other Qs will do for Iommi. I figure maybe the solder joints in the sockets are dicey, so I reflow everything in Q4 (and 5 for good measure), but now: no Iommi! Not for love or money. So now I go try to find where my good friend Tony is hanging out. I should mention that I used PF4393s by Central Semiconductor from Mouser, which you can find here. Otherwise, I try to follow the BOM religiously. When or why to choose MLCC vs. box caps for a given value when unspecified is another question I have, but maybe that's a separate thread.
Enter audio probe: Tony is (very) loud and proud along the whole component chain until Q4, where the signal distinctly dies and does not continue. I recheck and reflow everything in that section attached to Q4 (C12, C13, R16-20, and Q5). Nothing.
Switched the PF4393 transistors around in the sockets, all transistors give signal in Q2 and Q3 positions where there is signal, so I can't blame a faulty component.
I check continuity between transistor pins and solder joint, sockets and solder joints, and between sockets. Continuity checks out--I don't see anything that looks like a solder bridge even though there are some fat solder balloons on the component side of Q4 socket pins, but they don't appear to be touching. There also seems to be continuity between the sockets and C12/R16 and the sockets and R20/C13, although they just post dwindling value and never the beep (capacitors, am I right?).
Maybe it's a ground or voltage supply issue to Q4, I think to myself. Enter voltage probe: C12 and R16 show 6.18v prior to Q4. Q4, R20, and C13 read zeros or close to it.
Here are the rest of the numbers:
V in: 9.438
Transistors, reading Gate, Source, Drain (or pins left to right with the flats facing away from you)
Q1: 1.53, 2.12, 5.965
Q2: 0, 1.219, 5.022
Q3: 4.14, 6.822, 9.215
Q4: -0.243, 0, 0
Q5: 4.405, 6.184. 9.215
Q6: 4.188, 5.735, 9.215
Don't really know what to do besides maybe pull and reinstall another socket at Q4? Or maybe there is an issue with the voltage supply values?
Cheers, and you have what appears to be a lovely forum.