Ordered TL072 instead of TL022

[robthequiet]

Ah -- OK. So the theory is that the LFO voltages will modulate the clock circuit in the MN3101 which will in turn provide the BBD clock to the 3007. So you have two timing circuits, the LFO and the BBD. You may have stumbled onto a clue as to why the 3101 is apparently stalled. I can't fully explain how it works but the network around pins 5 and 7 on the MN3101 deliver the right amount off voltage/current to drive the speed of the MN3007 internal oscillator that varies according to the LFO. The values here are pretty critical. Do you have a DC voltage reading between IC4 pins 5 and 7 and does that change at all? Is your voltage reading at the cathode of D1 the same as IC4 pin 7?

It may seem tedious to take a lot of measurements, but what I try to do is isolate the problem. You seem to have good power and ground, and the LFO is doing something. So in my view the problem lies somewhere in the IC3 - IC4 region. Have you tried to adjust VR3? Does the voltage on pin 2 of VR3 match the other Vb points at R2, R7 and pin 5 of IC1? If you adjust VR3, do you see a change in voltage at these points?

[xorophone]

Ah -- OK. So the theory is that the LFO voltages will modulate the clock circuit in the MN3101 which will in turn provide the BBD clock to the 3007. So you have two timing circuits, the LFO and the BBD. You may have stumbled onto a clue as to why the 3101 is apparently stalled. I can't fully explain how it works but the network around pins 5 and 7 on the MN3101 deliver the right amount off voltage/current to drive the speed of the MN3007 internal oscillator that varies according to the LFO. The values here are pretty critical. Do you have a DC voltage reading between IC4 pins 5 and 7 and does that change at all? Is your voltage reading at the cathode of D1 the same as IC4 pin 7?

It may seem tedious to take a lot of measurements, but what I try to do is isolate the problem. You seem to have good power and ground, and the LFO is doing something. So in my view the problem lies somewhere in the IC3 - IC4 region. Have you tried to adjust VR3? Does the voltage on pin 2 of VR3 match the other Vb points at R2, R7 and pin 5 of IC1? If you adjust VR3, do you see a change in voltage at these points?

Sorry for not writing here in a while. I've been busy.

Between IC4 pins 5 and 7, there's a tiny modulation between 7.44 and 7.45v.
Yes, the voltage reading on the D1 cathode is the same as IC4 pin 7 (8.68-8.69v)

All the Vb points match VR3 pin 2 and I do see a change in voltage on all the points when adjusting VR3.

[robthequiet]

At this point I would make the executive decision to replace the MN3101 just because you could spend a lot of time verifying the circuit. Worst case you end up with a new MN3101 for another project. Time vs. money, that sort of thing. It's tough to probe around when you don't have a good working unit to compare it with.

There is one more thing I would try just for fun, not to be more tedious, which is to measure pin 2 and pin 6 on the MN3007 as you vary the VR3 pot slowly, maybe there is a magic point that will kick the chips into bucket brigading.

PS- Small Bear is a pretty good place to shop.

[xorophone]

At this point I would make the executive decision to replace the MN3101 just because you could spend a lot of time verifying the circuit. Worst case you end up with a new MN3101 for another project. Time vs. money, that sort of thing. It's tough to probe around when you don't have a good working unit to compare it with.

There is one more thing I would try just for fun, not to be more tedious, which is to measure pin 2 and pin 6 on the MN3007 as you vary the VR3 pot slowly, maybe there is a magic point that will kick the chips into bucket brigading.

PS- Small Bear is a pretty good place to shop.

I tried measuring pin 2 and 6 and chaning VR3, with no luck.

I just ordered some MN3101 and MN3007 chips from Banzai. I'll start by just replacing the MN3101 and if that doesn't work I'll replace the MN3007 too.

I'll come back as soon as I've tried the new chips. If it does work, I'll do everything to get my money back for the old ones, even though I ordered them a pretty long time ago.


Edit: I'd love to be able to order from smallbear, but the shipping costs to Europe are just way too high.

[xorophone]

At this point I would make the executive decision to replace the MN3101 just because you could spend a lot of time verifying the circuit. Worst case you end up with a new MN3101 for another project. Time vs. money, that sort of thing. It's tough to probe around when you don't have a good working unit to compare it with.

There is one more thing I would try just for fun, not to be more tedious, which is to measure pin 2 and pin 6 on the MN3007 as you vary the VR3 pot slowly, maybe there is a magic point that will kick the chips into bucket brigading.

PS- Small Bear is a pretty good place to shop.

Just a little update:

My chips, and several other guitar pedal parts, are stuck at a postal service terminal thing and have been so for 2 weeks now. They're supposed to be there for maybe 2 days max. I'll probably call them tomorrow and ask them what's going on, but I just thought I'd let you know what's going on..

[robthequiet]

Yeah, buying stuff online can be a mix. I got an SD card that was actually almost torn in two. I'm sure we have threads here about shady vendors. Hopefully Banzai has come through for you.

[xorophone]

Yeah, buying stuff online can be a mix. I got an SD card that was actually almost torn in two. I'm sure we have threads here about shady vendors. Hopefully Banzai has come through for you.

Yeah, it doesn't happen very often, but when it does, it's very annoying. I haven't contacted Banzai yet since it seems to be the postal service fault. I don't want to punish Banzai for someone elses mistakes. But on the other hand, they're a company and they probably don't lose a noticeable amount of money if they send me a new package.

[xorophone]

Yeah, buying stuff online can be a mix. I got an SD card that was actually almost torn in two. I'm sure we have threads here about shady vendors. Hopefully Banzai has come through for you.

I just got my chips! First I replaced the MN3101. The values already looked a lot better (I was getting a pretty good looking clock output). I played around with the trimpot but nothing was changing. I decided to replace the MN3007 too. Didn't work, but when I changed the trimpot the chorus kicked in!

So I'm guessing the previous chips were fake. I don't know if I'll be able to get my money back now (and I honestly feel kind of bad asking for it), but maybe I'll be able to get a little bit back at least... I shouldn't have to pay for something that doesn't work.

Well, now I just have to assemble it and then I'll finally be able to leave this project behind me.

Thank you Rob, you've been extremely helpful! And thanks to everyone else in the thread too!
"Man, I love this forum" I quietly whisper while shaking my head, tearing up.

[robthequiet]

Victory! Good troubleshooting, too -- rule out everything you can before blaming the parts, but only up to a point before you end up going around in circles. So that balance pot really can be critical, good to make a note of it.

And yes, this forum is a special place. 

[xorophone]

Victory! Good troubleshooting, too -- rule out everything you can before blaming the parts, but only up to a point before you end up going around in circles. So that balance pot really can be critical, good to make a note of it.

And yes, this forum is a special place. 

Yeah, I have a tendency to blame the parts too early, but I'm starting to learn how to properly troubleshoot something now. Yes, the trimpot is critical. That should be the first question to ask when someone needs help troubleshooting this pedal in the future. If they've played around with the trimpot.

And again, thank you so much for all the help! I wouldn't have been able to do all of this myself.