Deadend FX Mangel Wurzel no chorusing

[Fontelroy]

howdy folks,
first time poster here, I was directed over here from pedalpcb forums with the thought that someone here might be familiar with this project

I've currently got no chorusing happening with my deadend FX mangel wurzel which is a clone of an ibanez rotary chorus RC99

I have sound of bypass and when the circuit is engaged which is interesting considering this isn't true bypass so some stuff is working tho output B has noticeably more output/ gain than output A

I am currently using 4558's in place of the uPC4570 op amps the build docs call for as I'm waiting for their delivery which should be tomorrow. outside of that I'm using the sub parts the build doc has noted and have accounted for pinout differences with the transistors.

2 notes for the pics, I accidentally soldered a red wire for the 9v jack ground and didn't notice till i attached the pcbs together so i rolled with it and the pic showing q1 in the wrong pins has been fixed

[Mark Hammer]

Looking at the schematic, the 4570 chips might provide an improvement in noise specs, but don't seem at all necessary for normal functioning.  Were they used in the original?

My best recommendation here is to use an audio probe to trace progress of the signal through the circuit.  Audio probes can mimic the circuit-under-test "ending" at various points.  For instance, at pin 1 of IC1a or pins 3 and 1 of IC3a, as examples.  If you have audible signal at those points, then you know everything UP TO that point is functioning as it should, and any troubleshooting can safely ignore those parts of the circuit.

The probe itself is very simple.  It is just a regular patch cable, with whatever plug you need (1/4" or 1/8" phone) at one end and the other end consisting of an alligator clip to connect the shield to a suitable and convenient ground point, and the "hot" end terminated with a non-polarized capacitor; hopefully with a nice stiff and long lead that can be touched to various points on the circuit.  The lead does not have to be part of the capacitor.  Soldering one end of a standard voltmeter probe to the capacitor can work every bit as well, if not better.  Plug into an amp (with volume set low enough), turn the amp on, and with some signal source applied to the pedal circuit input, and the alligator clip secured to a ground point, touch the probe to various strategic points on the board, until you identify a place where the signal seems to just end abruptly.  That can also include the stompswitch.  Many forumites in past have overheated the solder lugs on a stompswitch, and caused the grease inside it to liquify, flow, and form an obstruction to signal.

[PRR]

https://drive.usercontent.google.com/download?id=1OpvxwDCM6n1V6RT3K5LvCE-sm3y7ayhj&export=download&authuser=0

> output B has noticeably more output/ gain than output A

They are the same circuit on the same signal. One of the output stages IC2_A or IC2_B has to be wrong. What's different?

[Fontelroy]

Looking at the schematic, the 4570 chips might provide an improvement in noise specs, but don't seem at all necessary for normal functioning.  Were they used in the original?

My best recommendation here is to use an audio probe to trace progress of the signal through the circuit.  Audio probes can mimic the circuit-under-test "ending" at various points.  For instance, at pin 1 of IC1a or pins 3 and 1 of IC3a, as examples.  If you have audible signal at those points, then you know everything UP TO that point is functioning as it should, and any troubleshooting can safely ignore those parts of the circuit.

The probe itself is very simple.  It is just a regular patch cable, with whatever plug you need (1/4" or 1/8" phone) at one end and the other end consisting of an alligator clip to connect the shield to a suitable and convenient ground point, and the "hot" end terminated with a non-polarized capacitor; hopefully with a nice stiff and long lead that can be touched to various points on the circuit.  The lead does not have to be part of the capacitor.  Soldering one end of a standard voltmeter probe to the capacitor can work every bit as well, if not better.  Plug into an amp (with volume set low enough), turn the amp on, and with some signal source applied to the pedal circuit input, and the alligator clip secured to a ground point, touch the probe to various strategic points on the board, until you identify a place where the signal seems to just end abruptly.  That can also include the stompswitch.  Many forumites in past have overheated the solder lugs on a stompswitch, and caused the grease inside it to liquify, flow, and form an obstruction to signal.

I'm not sure if this would help in my situation tho, I'm getting dry signal in both bypass and when the signal is engaged, no wet

[eh la bas ma]

I'm not sure if this would help in my situation tho, I'm getting dry signal in both bypass and when the signal is engaged, no wet

Yes, so you need to find why there isn't any wet signal. In other words : where is the issue(s). An audio probe is the cheapest, easiest, quickest and most "diy" way to locate the problem.

To have a wet signal, you need your signal to go through the circuit, into the BBD section and out of it.

Following the schematics, you probe the signal path until you find something suspicious. That's how you narrow it down. We can help you find the signal path, if you are confused.

Usually, it's a bad connection or a short somewhere, so you follow the signal and when it stops, you check the aera. You will probably find a soldering pad where you should have a signal but you can't hear it with the audio probe, then you have found your culprit.

This method is much more effective than just looking at your pcb, reflowing here and there, trying to find some needle in a haystack, right ?

https://diy-fever.com/misc/audio-probe/

If you build some very simple circuit with very few parts, you might be able to manage without the audio probe to debugg it. With modulation circuits, with 2 stacked pcb and all the houp-la-boum, if it doesn't work you are going to need an audio probe badly.

You can also post some voltage readings, just as described in this very useful article : https://www.diystompboxes.com/smfforum/index.php?topic=29816.0

Last thing that comes to mind : BBD chips need to be biased to be able to modulate the signal (usually it's around 3.5V, if i am not mistaken), so i guess there is also a chance that your circuit works, but it's not calibrated correctly so it sounds like nothing happens, only dry signal. I hate multi-turns trimmers, i'm always completely lost with these, just turning and turning for ever... Regular trimmers are much easier to use, in my experience. If it was my build, i'll replace every trimmers...

[Fontelroy]

okay, I gotcha now, I've been doing what you said in the meantime and I stitched together the schematic for the chorus and linked it. For the wet signal path I'm getting signal until pin 3 of the MN3207, I have a few options I've tried and none seem to work, I've pulled known working chips from a previous flanger project and no dice. I took voltage readings of the bbd's
IC5 - 3207
1 - 0.1mv
2 - 3.0v
3 - 5.7v
4 - 6.7v
5 - 7.23v
6 - 3.3v
7 - 7.35v
8 - 7.81v
IC6 - 3102
1 - 7.17v
2 - 3.1v
3 - 0.1mv
4 - 3.14v
5 - 6.6v
7 - 330mv
8 - 6.8v

[eh la bas ma]

I think you need to be around 3.4V, or somewhere between 3.3V and 3.8V at pin3 of the MN3207 ?

I could be wrong, but that's how it's calibrated on some other BBD chorus i've built.

See if you can adjust it with a trimmer ?

Inject some signal in the effect, and listen for some modulation as you turn the trimmer in this 3.3V - 3.8V aera. Remember to set the controls so you can hear the modulation, don't turn the Mix knob fully CCW for example.

[Fontelroy]

Holy frijole folks, I warmed up a suspicious looking solder pad on IC5's socket and we're in business. My basement is chorus city!       

[eh la bas ma]

Nice, now you can build the Blue Shift ?

An other easy build with 2 stacked boards !

https://aionfx.com/app/files/docs/blueshift_documentation.pdf

[Fontelroy]

I've built the blueshift, this rotary chorus is kicking it off my home board for the time being, but the dc2 clone sounds great! it's a much better/easier build imo. the dead end is a soldered sandwich as its designed, the blue shift is made to come apart which makes for MUCH easier troubleshooting

[Fontelroy]

thanks for all the help and suggestions folks, I don't know if it'd have fixed it tonight without finally putting together an audio probe

[Mark Hammer]

Congrats.  The Ohio and Allegheny have come together!

[digi2t]

I've built the blueshift, this rotary chorus is kicking it off my home board for the time being, but the dc2 clone sounds great! it's a much better/easier build imo. the dead end is a soldered sandwich as its designed, the blue shift is made to come apart which makes for MUCH easier troubleshooting

They don't need to be soldered together. The use of pins and sockets are highly recommended, specifically for troubleshooting, as well as assembly ease. I would never solder the two boards together. Otherwise, it's a Murphy moment waiting to happen.

[Fontelroy]

Your build doc say otherwise. How the heck is it fitting in your specified 1590BBS enclosure?

[Fontelroy]

I've built the blueshift, this rotary chorus is kicking it off my home board for the time being, but the dc2 clone sounds great! it's a much better/easier build imo. the dead end is a soldered sandwich as its designed, the blue shift is made to come apart which makes for MUCH easier troubleshooting

They don't need to be soldered together. The use of pins and sockets are highly recommended, specifically for troubleshooting, as well as assembly ease. I would never solder the two boards together. Otherwise, it's a Murphy moment waiting to happen.

Do you think you might want to update your build docs?