I've just built the Coral Chorus from Tonepad, but I accidentally ordered a TL072 instead of the TL022. I still put it in the circuit, but it didn't work. The guitar signal goes through the circuit, but no chorus is applied. Since I'm not using the right op-amp, I don't want to start the fault diagnosing process before I know if the TL072 will even work the slightest. I'll of course order the right chip and replace it as soon as possible, but if something else is wrong with the pedal, I'd like to fix that while I'm waiting.
I've included every mod on Tonepad's PDF. None of the potentiometers (including the depth) make any difference to the sound, but when I touch the lugs on the depth pot, it generates a hum that I can control the volume of by turning the knob. The bass and chorus intensity switches don't change the sound at all either, but as soon as i deactivate (or activate?) the vibrato switch (when I disconnect R21), the guitar signal goes away completely.
Could these issues be related to the chip, or do I need to start fault diagnosing the rest of the circuit? If anyone has a list of measured voltages from IC's etc, I'd love to see them, but I can probably find them easily through a Google search.
Edit: When I look at the schematic, I understand why the signal goes away when I disconnect R21. I'm basically just disconnecting the dry signal and since there is no wet signal in the circuit, nothing is going to the output.
http://www.tonepad.com/project.asp?id=53
Do you have a schematic where we can refer to?
Verstuurd vanaf mijn Lenovo P2a42 met Tapatalk
Quote from: niektb on May 27, 2017, 04:51:10 PM
Do you have a schematic where we can refer to?
Verstuurd vanaf mijn Lenovo P2a42 met Tapatalk
Sorry! Forgot to link it. :icon_redface:
Here it is: http://www.tonepad.com/project.asp?id=53
Scroll down and click the pdf link under "Layouts".
It would be good to have images of your build, front and back and large enough so that we can read the component values and verify the wiring. Also, do you have an audio probe to check where the signal gets lost?
Quote from: robthequiet on May 27, 2017, 05:21:17 PM
It would be good to have images of your build, front and back and large enough so that we can read the component values and verify the wiring. Also, do you have an audio probe to check where the signal gets lost?
I can upload some images and voltage measurements tomorrow. Yes, I have an audio probe, but I'd like to know if the TL072 will create any significant problems before I get too deep into the audio probing, since that might be the only problem with the circuit. But if no one knows, I'll start audio probing it while I'm waiting for the new chips and hope for the best. :)
The wiring should be fine, since the input, output, ground, power and bypass are working.
Hi--
I can't help with the debug, can assure you that the TL072 is the way to go. It's pin-for-pin compatible with the long-obsolete TL022 and is known-to-work in the Coral.
Regards
SD
Quote from: smallbearelec on May 27, 2017, 05:55:35 PM
Hi--
I can't help with the debug, can assure you that the TL072 is the way to go. It's pin-for-pin compatible with the long-obsolete TL022 and is known-to-work in the Coral.
Regards
SD
Thank you so much! That's really good to know! :) Then I'll just have to start debugging it tomorrow. I know how to do that, but I'm still pretty bad at it, so I'd love some voltage measurements if someone has them. It just makes it a bit easier if I know where I should expect signal.
Oh, and on the - input of op amps I shouldn't be able to hear any signal while audio probing, right? Is it the same on any other places in the circuit? (except ground and power supply tracks of course.)
If you look through the builds reports for the project on the Tonepad site, you'll see that many use the TL072 instead of the TL022 - and some think it sounds better.
Since when is the TL022 obsolete?
http://www.mouser.com/ProductDetail/Texas-Instruments/TL022CP/?qs=tJ5HNKWh3OXMoEOaPjTJiA%3D%3D
The TL022 and the TL072 may be pin for pin compatible....but in many builds with multiple op amps or an LFO...the TL022 is used for it's lower current draw. (65 uA TL022 compared to 1.2ma TL072)
+1. You may be barking up the wrong tree, worrying about the '22. Maybe post some voltages?
Quote from: blackieNYC on May 27, 2017, 09:44:38 PM
+1. You may be barking up the wrong tree, worrying about the '22. Maybe post some voltages?
Voltage measurements with all pots at around 12 o' clock:
IC1 (RC4558P)
1. 4.33v
2. 4.33v
3. 4.33v
4. 0v
5. 4.33v
6. 4.33v
7. 4.33v
8. 8.86v
IC2 (TL072. TL022 in project file)
1. Modulation between ~1.5v and ~7.5v
2. Tiny modulation around ~4.4v
3. Modulation between ~2.5v - ~5.5v
4. 0v
5. Tiny modulation around ~4.4v
6. Tiny modulation around ~4.4v
7. Modulation between ~2.5v - ~5.5v
8. 8.86v
IC3 (MN3007)
1. 8.83v
2. 0v
3. 1.42v
4. 0.05v
5. 0v
6. 8.83v
7. 8.81v
8. 8.81v
IC4 (MN3101)
1. 8.83v
2. 8.83v
3. 0v
4. 0v
5. 0.01v
6. 0.02v
7. 8.83v
8. 0.19v
I'm guessing the TL072 is used as the LFO, which describes all the modulation that's going on. Something that worries me a bit is that pin 1 on the MN3007 chip is connected to 9v, but on the pinout that's supposed to be the ground pin... Please tell me if I should measure any other components, for example the transistors.
Something I have noticed is that my 3007 and 3101 chips look very salvaged or even fake. The mn3007 chips have solder left on the pins, suggesting they're salvaged. The mn3101 chips look relabeled because they've got a square around the label on the top. The salvaged chips might still work, but the relabeled ones are really worrying me. I don't want to buy new chips before I know if they work though. I've done that before.
Here are some pictures of the circuit board and the possibly fake chips. As you can see, the etch really didn't turn out nice this time, but I've checked the obviously unreliable connections and they seem fine. I might of course have missed something though. It was hard getting a good picture of the chips, but you might be able to see that the right chip (MN3101) has been relabeled or something and that the pins on both chips have blobs of solder and crud on them. I ordered 4 chips and the MN3101 I have in my circuit didn't have the dirt and solder on the pins.
(http://i.imgur.com/4ns63yth.jpg)
(http://i.imgur.com/AJfWEoGh.jpg)
(http://i.imgur.com/UIQJ1qCh.jpg)
QuoteSomething that worries me a bit is that pin 1 on the MN3007 chip is connected to 9v, but on the pinout that's supposed to be the ground pin...
This is a P-channel device. Convention is for these to be shown as positive ground, negative supply. So the + supply is marked as 0v or Ground and the - supply is Vdd. To use in a normal negative ground, positive supply circuit, the chip Gnd is +9v and the Vdd supply pin is connected to 0v. That keeps the polarity correct.
Confusing isn't it ;)
(http://tonebuster.org/images/effects/f_ch10/mn3007_pinout.png)
Quote from: anotherjim on May 28, 2017, 08:54:55 AM
QuoteSomething that worries me a bit is that pin 1 on the MN3007 chip is connected to 9v, but on the pinout that's supposed to be the ground pin...
This is a P-channel device. Convention is for these to be shown as positive ground, negative supply. So the + supply is marked as 0v or Ground and the - supply is Vdd. To use in a normal negative ground, positive supply circuit, the chip Gnd is +9v and the Vdd supply pin is connected to 0v. That keeps the polarity correct.
Confusing isn't it ;)
(http://tonebuster.org/images/effects/f_ch10/mn3007_pinout.png)
Ah, I understand! (almost :icon_biggrin:)
So the mn3007 voltages look right?
I just did some audio probing and I'm hearing the signal all the way to pin 3 on the mn3007. All other pins are quiet. I also fixed a suspicious looking solder joint and checked some continuity. Everything looks right to me. Can someone please take a look at the voltage measurements and tell me if they look good? Is there something else I should check before I conclude that the chips are fake?
Theoretical question: If there is no output from the BBD, it means that there is no clock to pulse the signal across the 1024 stages for output?
If the clock is coming from the 3101, would we not hear a fizzy noise on the 3007 pins 2 & 6?
Will the 3007 pass some kind of audio even if the clock is not present?
Just thinking out loud here. ???
Quote from: robthequiet on May 28, 2017, 02:33:25 PM
Theoretical question: If there is no output from the BBD, it means that there is no clock to pulse the signal across the 1024 stages for output?
If the clock is coming from the 3101, would we not hear a fizzy noise on the 3007 pins 2 & 6?
Will the 3007 pass some kind of audio even if the clock is not present?
Just thinking out loud here. ???
Those are actually good questions. If the 3101 provides the clock and there's no output from the 3007 without the clock source, it might as well be something wrong with the 3101 (or the wiring around it), rather than the 3007.
Still need someone to take a look at my voltage readings. ;)
To me, IC1 and IC2 look pretty happy. Also, the fluctuations on IC2 suggest that the LFO is doing something. Need to consult datasheets for the BBD chips, but maybe there is a forumite who has the answer...
Quote from: robthequiet on May 28, 2017, 10:15:21 PM
To me, IC1 and IC2 look pretty happy. Also, the fluctuations on IC2 suggest that the LFO is doing something. Need to consult datasheets for the BBD chips, but maybe there is a forumite who has the answer...
Yeah, IC1 and 2 look fine, but I've never used BBD chips before, so I don't know how they're supposed to work. :-\ I think the thread subject might make a lot of people ignore it too, since the topic has changed completely. I don't know if there's any rules regarding thread subject changing and stuff though.
When I get home today I'll check if the LFO from IC2 makes it all the way to the 3101. Knowing that should help me a lot. Don't know why I haven't checked that before. ;)
Yep. What I was looking for was the clock signal getting from the 3101 into the 3007 -- my fear is that the 3101 is stalled, but checking for clock signal with a meter is not straightforward -- if you have a meter that measures frequency it should show some activity on both pins (MN3101 pins 2 & 4). If you put it on AC and measure each pin you should get some kind of reading on both clock pins, not hard Vdd on one and ground on the other. If you had access to an oscilloscope you would find out rather quickly what the status is.
Just for kicks, you could check for continuity (power off) on the clock pins:
MN3101 -> MN3007
pin 2 -> pin 6
pin 4 -> pin2
Looking forward, it may be worth considering getting sockets and new chips after we rule out any other component or PCB issues.
Quote from: robthequiet on May 29, 2017, 11:58:55 AM
Yep. What I was looking for was the clock signal getting from the 3101 into the 3007 -- my fear is that the 3101 is stalled, but checking for clock signal with a meter is not straightforward -- if you have a meter that measures frequency it should show some activity on both pins (MN3101 pins 2 & 4). If you put it on AC and measure each pin you should get some kind of reading on both clock pins, not hard Vdd on one and ground on the other. If you had access to an oscilloscope you would find out rather quickly what the status is.
Just for kicks, you could check for continuity (power off) on the clock pins:
MN3101 -> MN3007
pin 2 -> pin 6
pin 4 -> pin2
Looking forward, it may be worth considering getting sockets and new chips after we rule out any other component or PCB issues.
I made some measurements again, with some very interesting results. First I checked continuity between the pins you suggested. They were fine.
I did have an oscilloscope which I used to measure the clock signal from the TL072, until I got to R36... then it stopped working... (the oscilloscope) ??? I continued measuring with my multimeter, which worked pretty well. I realised that there was clock signal up until the anode on D1, but not on the cathode. Instead I measured about 8.7v (which seemed to have a tiiiiny 0.01v modulation). Looking at the schematic, there isn't supposed to be 9v in that part of the circuit, right? It's supposed to go through both R52 and R38 and get lowered quite significantly, if I'm understanding it correctly. I checked continuity between the cathode of D1 and the cathode of D7, but there is no continuity. I'm just getting really confused at this point. :icon_cry:
The reason I didn't use sockets was because I have to fit the circuit board under the 1/4" jacks. I could have used them on the 3007 and 3101 side of the circuit board though... I don't know why I skipped them. At least I used one for the TL072.
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?
Quote from: robthequiet on May 29, 2017, 11:54:14 PM
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.
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.
Quote from: robthequiet on June 04, 2017, 03:28:16 PM
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. :(
Quote from: robthequiet on June 04, 2017, 03:28:16 PM
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..
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.
Quote from: robthequiet on June 25, 2017, 08:05:30 PM
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. ;)
Quote from: robthequiet on June 25, 2017, 08:05:30 PM
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! :D
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.
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. 8)
Quote from: robthequiet on June 29, 2017, 02:01:44 PM
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. 8)
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.