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I tried this on my KORG Volca Bass and had the same result. Apparently KORG sets one of the pins differently and the Altura does not like that. Hmmm. Who knows? I tried the Altura on several other MIDI-enabled synths (Dave Smith, Arturia, Roland, etc) and had no trouble… it appears to be unique to the Volcas. I’m wondering if you could change a setting on either the Altura or the Volca (not that there’s many settings on the Volca to change) and get it to work.
Thanks for the great suggestions Brach. I think I found the problem. I unplugged the 2 mic/speaker daughterboards during the switch/jack troubleshooting and then plugged them back in again after we fixed that. Somehow, I got one of them reversed when I plugged them back in. I just unplugged both from the board, powered it up and bam… 5V at the left side of U5. I plugged them both in correctly, powered it back up and… you guessed it… I see digits on the LCD.
That’s good to know for future reference. If one of the 2 daughterboards is backwards, you’ll see low output at U5. Ugh… that was frustrating. I was so focused on looking at the solder joints, I completely missed the fact that one of the ribbon cables was backwards. D’oh.
In any case, thanks for your help on the switch issue. That one was legit and not just me being absent-minded.
Okay. First problem solved and on to the next… I metered at U5 and I’m seeing the values below. Shouldn’t I be seeing 5V on the left side of U5? Coincidentally, I’m seeing the same voltage (0.8V) across pins 8 & 16 of U3. What would be causing U5 to read that low? I’m using the A/C adapter BTW.
Thanks so much Brach. Some great suggestions. After testing all the continuity joints, I used a jumper wire to make the connection below and now the power light comes on. Progress! Alas, I’m not seeing any lit segments on the LCD screen. I’m checking the Troubleshooting Guide now to see what it says about that. I guess the fun just doesn’t stop on this one. Sheesh. Is Mercury in retrograde?
Another graphic to help visualize…
It seems to me that there are 2 problems going on: 1) 9V power not getting to the switch, 2) switch not conducting. I’m going to hold off on removing the jack for now. I’d like to hear what you folks think.
Sometimes a picture is worth 1000 words. The green line indicates continuity. The red arrows are the places where I can see 9V.
Okay… I just did some more troubleshooting. I checked for continuity across the switch. The only place I’m seeing continuity is across the diagonal posts (furthest forward and backward). I’m assuming those are both ground and that’s why but I have no continuity across any of the other 6 pegs. I tried all combinations of L and R. Also, I discovered there is 9V power at C8. So maybe it’s not the jack… great suggestion Brach.
I get your logic Brach, it makes perfect sense, but I think you missed the part where I said there is no voltage on EITHER SIDE of switch. So, the power is not getting from the power jack (or battery… I tried with both) to the switch. I can see 9V at the actual terminals of the jack (so I don’t think the jack itself is bad), but it could still be shorted where it meets the board (sloppy solder, stray wire, who knows).
So, unless you can think of something else (I’m certainly open to other ideas), I’m assuming the jack needs to be removed, cleaned off, and re-soldered. I was going to try that today. The reason I wanted a replacement part is because I think that jack is going to be difficult to remove from the board and I may damage it in the process.
Thanks for the help guys. Great suggestion by Roy.
I checked and I’m not seeing 9V on either side of the switch. Hmmmmmm. So I guess something is going on with the DC jack??? I’ll try desoldering that from the board and see if there’s a glob of solder or something like that on the underside that’s shorting it out. I’m not really sure what else it could be.
I might be better off to just buy another port and try again. Does anyone know the Mouser part# for this port?
Thanks again for the excellent suggestion Brach. I went to desolder the pot from the board and noticed something I hadn’t before. The manual has us tack the pots in place on the top and then solder them on the bottom. Well, the tack on the center pin of the rate pot had a “tail” coming off of it and it was dangerously close to R29. I think you can see where this is going… I got out the desoldering braid… slurped the excess solder up and guess what… the rate knob works perfectly.
Ugh. I guess the sloppy solder was close enough that it was involving R29 in the circuit and thus why the knob was metering so wonky. I’ve now re-tested everything with the meter (and with audio) and it seems like the pedal is working flawlessly. The only thing I haven’t tested yet is MIDI. I’ll do that later.
Anyway… I am so sorry… I don’t know how that happened but obviously I got sloppy on that one tack. FWIW, I double-checked all the rest of the pots and they’re all clean. I’m sorry for making you work so hard to diagnose my sloppy soldering. I am really embarrassed.
Regardless… I can’t tell you how much I appreciate your help even if it was my mistake all along.
Again… great insight Brach and thank you for all your help.
I pulled the microcontroller with my IC puller (side note… all pins are nice and straight). Then I powered up the pedal and metered pin24 to ground while turning the rate knob.
When the rate knob is fully counterclockwise, I’m seeing 0.19V at the IC socket. Then as I turn the knob clockwise, I see small scaling increase until I hit about 1/8 travel. At that point, it jumps to 4.98V and remains there for the rest of the wipe. To clarify, I’m seeing 4.98V for about 7/8 of the pot’s sweep.
I love the way you think Brach. Great suggestion and I have some more findings.
With the power off, I metered from pin 24 of the IC to ground and swept the rate knob. I found the values ranged from 0 Ω to 3.28 KΩ (that’s not a typo… I attached a pic – it’s a little difficult to see the small K in the lower left of the screen but it’s there). I also metered directly on the center lug of the rate pot to ground and I’m getting the same range – 0 Ω to 3.28 KΩ.
I stopped troubleshooting there and didn’t bother removing the IC. I believe this tells us the circuit is solid from the pot to the IC and the pot is probably our culprit but I’d love to hear your analysis as you seem to have a great understanding of this circuit. Again… thank you so much.
Brach, thank you again for the great troubleshooting advice. I was able to test the pedal today. Here’s what I found…
-Center pin of rate pot to pin 24 on IC is a good connection (metering at the IC itself)
-Rate pot has good 5V (4.98 to be exact) current on right (based on bottom view) lug
-Rate pot has solid ground on left lug
-Center lug of rate pot is metering 4.98V regardless of the position of the wiper (unless you turn it all the way counterclockwise and then it meters 0V)Basically, the rate pot passes 0V when fully counterclockwise. As you turn it slightly clockwise, it jumps to 5V and stay there for the rest of the wipe.
It sounds to me like I may have a defective pot but I’d like to hear you’re opinion.
