BOSS CE-2 AION FX CLONE ISSUES

[midwestrepairdesk]

I built up a Boss CE-2 clone from Aion FX (model name Azure) and I'm only getting a clean (non-chorus) output from the pedal. I've included schematics and voltages measured. I'm hoping someone can help me because I am stumped.

Why my chorus no chorus?

I probed pin 1 of the blend pot with a 100n cap in series straight into my interface and into audacity to monitor still no chorus effect present. I probed around IC2 and IC3 on the oscilloscope and found a square wave coming off of pin 2 of IC2 looking at the datasheet it seems to be the clock frequency, so it is functional. I'm drawing blanks here.


Below are my current measurements,






Link to build docs,

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

[midwestrepairdesk]

Here is a link to the build documents.

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

[midwestrepairdesk]

I stepped away for a few hours and came back to it. Replaced IC1 with a new 4558 and put back in the original IC4 TL022. I probed pin 1 of the blend pot with a 100n cap in series straight into my interface and into audacity to monitor still no chorus effect present. I probed around IC2 and IC3 on the oscilloscope and found a square wave coming off of pin 2 of IC2 looking at the datasheet it seems to be the clock frequency, so it is functional. I'm drawing blanks here.


Below are my current measurements,

[Baran Ismen]

I've recently made the Tonepad version, which is pretty much the same. I've noticed that trimpot there is to find a balance for blending the chorus and clean sound. Make sure its correct value and set properly, because in my case, half of its turn seems to give a chorus sound and I set it to around %25 for a balanced, non-distorted chorus sound. You may give a try with multi-turn trimpots for a more precise balance. Apart from that, as long as the BBD's are correct it should work out of the box.

[duck_arse]

and welcome to the forum. your TL022 voltages look not good. can you o'scope pins 1 and 7 to see if that oscillator section is working please?

[ElectricDruid]

Welcome!

If you've got an o'scope, check for clock signals on pins 2 and 4 of the MN3102, and at the other end, pins 2 and 6 of the BBD. If those are present (even if the LFO isn't working) you should have some delay signal. You can check for that at C13, but it'll look cleaner at Q3 emitter/C17, if it makes it that far.

IF there's no delay signal, check Q2 emitter to make sure that you've got a signal *going into* the BBD! If that filter were bad, you'd get no delayed signal because it's not seeing any input.

"Clock not working" is the most common fault in my experience though, hence why I asked you to start with those clock pins.

Good luck!

[midwestrepairdesk]

Welcome!

If you've got an o'scope, check for clock signals on pins 2 and 4 of the MN3102, and at the other end, pins 2 and 6 of the BBD. If those are present (even if the LFO isn't working) you should have some delay signal. You can check for that at C13, but it'll look cleaner at Q3 emitter/C17, if it makes it that far.

IF there's no delay signal, check Q2 emitter to make sure that you've got a signal *going into* the BBD! If that filter were bad, you'd get no delayed signal because it's not seeing any input.

"Clock not working" is the most common fault in my experience though, hence why I asked you to start with those clock pins.

Good luck!

I have clock signal at all four pins mentioned above. If I input a signal to the pedal (1k sine wave @ 500mv AC.RMS) I measure 178mv AC.RMS at the emitter of Q3.


Below are all AC RMS measurements.

Mix:   
   
     CW:
     Pin 1     100mV   
     Pin 3     176mV   

     CCW:
     Pin 1     177mV   
     Pin 3     28mV   

     Noon:
     Pin 1     177mV   
     Pin 3     50mV   
      
Output:   

     465mV   
      
IC1 (AC)   
   
     Pin1     1.2mV   
     Pin2     0.00mV
     Pin6     0.00mV   
     Pin7     473mV   
      
IC2 (AC)   
   
     Pin2     4.38V     @     85.5khz
     Pin6     4.38V     @     85.5khz
     Pin7     520mV   @     580khz
      
IC3 (AC)   
   
     Pin2     4.40V @   85.65khz
     Pin4    4.38V @   85.65khz
     Pin5    1.25V @   165khz
     Pin7    1.23V @   67.8khz

Q2      

     B     388mVAC  @  1khz

Below are all DC RMS measurements.

         E         B        C         
Q1   4.54   4.93   9.23      PWR   9.50
Q2   4.87   5.40   9.23      VA   9.25
Q3   4.66   5.09   9.23      VB   5.63
Q4   0.00   0.35   7.62      VC   4.59
Q5   2.27   2.91   9.23      VD   8.77

I hear absolutely no difference between effect engaged and effect off. There is only a slight volume drop when pedal is engaged that's too small to hear but can be measured.

Effect off output (500mVAC)
Effect on output (465mVAC)

[midwestrepairdesk]

I don't understand why I can't get a view of the signal on the oscilloscope on pins 2 and 6 of IC1. The signal is present at the junction of C3 and R4. Replaced R4, signal still not present after R4 @ pin 2 of IC1. I removed R5 because it's paralleled in to remove it from the equation STILL no signal present after R4. I also verified the removed R5 with a multimeter to be within spec.

[ElectricDruid]

I don't understand why I can't get a view of the signal on the oscilloscope on pins 2 and 6 of IC1.

That's an easy one! It's because those are virtual ground points. They're inverting op-amp stages.

One way to think about it is that the signal coming into that point is matched and cancelled out by the feedback signal coming through the resistor from the op-amp's output. Since the two signals cancel at that point, you don't see anything.

[midwestrepairdesk]

That's an easy one! It's because those are virtual ground points. They're inverting op-amp stages.

One way to think about it is that the signal coming into that point is matched and cancelled out by the feedback signal coming through the resistor from the op-amp's output. Since the two signals cancel at that point, you don't see anything.

Ok, that makes sense. Thank you for explaining. Now the question remains why chorus no chorus??

[ElectricDruid]

Ok, that makes sense. Thank you for explaining. Now the question remains why chorus no chorus??

You said the clocks were ok, so have you got a delayed signal at the output of the BBD?

[midwestrepairdesk]

You said the clocks were ok, so have you got a delayed signal at the output of the BBD?

I measured the input signal vs the emitter of Q3 and am seeing a delay in signal that is variable based on the "depth" knob's position.

[midwestrepairdesk]

Should I be hearing a chorus sound coming from pin 1 of the mix control? Or does this effect happen when the dry and wet signals mix together via the control during the last opamp stage?

[midwestrepairdesk]

The Depth control is controlling the clock frequency it seems. It varies between 75-100khz. This was measured at pins 2&6 of IC2. The Rate control varies the amplitude of the waveform shown on the oscilloscope. It fluctuates by about 0.3mV. That was measured at the output.

[ElectricDruid]

I measured the input signal vs the emitter of Q3 and am seeing a delay in signal that is variable based on the "depth" knob's position.

Ok, that's a good sign, since it means the BBD is working.

Should I be hearing a chorus sound coming from pin 1 of the mix control? Or does this effect happen when the dry and wet signals mix together via the control during the last opamp stage?

It happens when they're mixed in the last op-amp stage. Pin 1 of the mix pot is just the delay signal. If the LFO was working, you'd hear a warbly vibrato signal there, but since what you've got is a fixed delay, it sounds pretty much like the straight signal.
The effect vs bypass signal should be *slightly* different, since the effect has a marginally delayed copy of the signal mixed in. You should be able to hear a difference in tone. It'll be fairly subtle though. If you waggle the depth knob while listening to the effect, you'll have some kind of "manual chorus" where you're the LFO.

The Depth control is controlling the clock frequency it seems. It varies between 75-100khz. This was measured at pins 2&6 of IC2. The Rate control varies the amplitude of the waveform shown on the oscilloscope. It fluctuates by about 0.3mV. That was measured at the output.

It sounds like there must be something wrong in the LFO, since everything else seems to be ok. Check that part over carefully.

[midwestrepairdesk]

It sounds like there must be something wrong in the LFO, since everything else seems to be ok. Check that part over carefully.
[/quote]

You sir are correct! Thank you. I found a 4k7 in place for the R30 47k feedback resistor in the first half of IC4. I'd like the effect to be louder but, it's functional! I need to boost the signal coming from Q3 I think to achieve that goal.

[antonis]

I'd like the effect to be louder but, it's functional! I need to boost the signal coming from Q3 I think to achieve that goal.

The way the MIX pot is utilized complicates things a bit..
In case your issue is output louness, better focus on IC1B  stage gain, hence R9 value..
(C5 and R10/C6 can wait for next step, if needed..)

P.S.
Before doing anything, verify R25(1M) proper value..

[midwestrepairdesk]

P.S.
Before doing anything, verify R25(1M) proper value..

Verified R25 as 1M. As far as IC1's first half goes. Correct me if I am wrong, but R7 and R5 are setting the gain of that stage. R4 comes into play but it is controlling the gain of select frequencies because it forms a high pass filter?
I was reading the analysis on https://www.electrosmash.com/boss-ce-2-analysis#link6 and I am a bit confused when they talk about the signal going into the 3207 being "sampled". My intial thought is that increasing the gain wouldn't make a difference since the signal is being "digitized" or am I completely wrong? This is my first time messing with anything besides transistor and opamp based overdrives/distortions.

Thanks!

[antonis]

As far as IC1's first half goes. Correct me if I am wrong, but R7 and R5 are setting the gain of that stage. R4 comes into play but it is controlling the gain of select frequencies because it forms a high pass filter?

Quite right..
More precisely, R5//(R4+C3) + C2 + Q1 output impedance form a complex HPF..
(R3+C3 bypass R5 in the same way R10+C6 bypass R9 but with opposite effect due to NFB loop placement reverse action..)

IC1A midband gain is unity, as well as IC1B mixing stage does for MIX pot set FCW..
Clean signal gain is set by R9/R8 where dirty signal gain is set by R9/(R23+MIX wiper-lug3)..
I'd propose to use an audio probe to verify both clean & dirty signal amplitudes(*) to properly proceed to individual or total boosting..

(*)i.e. on IC1A pin 1 and on C17/R25/MIX wiper-lug1 joint..

[duck_arse]

post photos why not