Help on ADA flanger from moosapotamus PCB

[BootCut]

Hi,

I bought this PCB from Charlie at moosapotamus, it's rev 5.
http://moosapotamus.net/IDEAS/ADAflanger/ADA_MN3007/ADAflanger_MN3007.html

I populated the board and adjusted T4 and T5 to get ~70kHz for the low point and 2.6MHz for the high point of the sweep. When I try it out it doesn't sound very good. Alot of awful distorsion and no flanging at all, to my ear.

I have uploaded this file on youtube if it helps.
http://www.youtube.com/watch?v=K-jkhNRBtlg

I have checked voltages for all IC's. The result is quite close to what oldschoolanalog measured from his working board.
http://www.diystompboxes.com/smfforum/index.php?topic=74367.msg710731#msg710731
http://www.diystompboxes.com/smfforum/index.php?topic=74367.msg710840#msg710840

PIN   4007      4047           3007        4049
1       NC          14.6 - 10.3    14.5        14.7
2       NC          0.14 - 4.6      7.4          7.4
3       0             8.2 - 8.1        9.4         7.4
4       NC          14.7               1            7.4
5       NC          14.7               0            7.4
6       0             14.7              7.4          7.4
7       0             0                   9 - 7.3    7.4
8       NC           0                   9 - 7.3    0
9       NC           0                                 7.4
10     6.3 - 3.9  7.4                              7.4
11     8.2 - 8.4  7.4                              7.4
12     0.2 - 4.6  0                                 7.4
13     NC           14.6 - 10.6                  NC
14     14.7        14.7                            7.4
15      NC                                             7.4
16      NC                                            14.7            


Pin  IC1    IC2   IC3         IC4
1     7        4.7     7            12.9
2     7        4.7     7            7.3
3     6.3     4.7     7            ~2.5 - ~11.9
4     13.9   13.9   14.4        0
5     9.3     6.7     7             7
6     9.4     6.7     7.2          7
7     9.4     2.8     7.4         ~3.1 - ~11.3
8     8.7     7        6.3 - 3.9   14.4
9     7        7        5.5   
10   7        7        5.5   
11   0        0        0   
12   8.6     6.9     3.8   
13   8.6     7        3.9   
14   8.6     7        2.2 - 11.4   


I have checked all solder joints, no issue there.

Any suggestions how to move on in my troubleshooting?

Thanks!

/Daniel

[oldschoolanalog]

First; did you calibrate it as per the instructions Charlie posted in his project file?
Second; my clock f measurements were taken at the BBD. Not the "test point".
Third; have you audio probed it? If not, do so.
Fourth; IC2 pin 7 in way off compared to the V's I posted. That's the output of the unit. Hmm...
Fifth (add last for now ); Check the BBD bias first. Work slowly and patiently.
Good Luck! Report back...

[BootCut]

1. I did calibrate it, as far as I could, according to the project file from Charlie. However, I couldn't calibrate the BBD using the test method from ADA. The scope was unable to read that weak signal.
2. I measured f both from TP and pin 10/11 from 4047. The frequencies from pin 10/11 (35kHz - 2,6MHz) are doubled at the TP. I believe this is correct.
3. I did audio probe it. But I'm a bit lost here, I don't know what I'm looking for. Here is my result.
IC1 pin 1 (A): clean boost signal
IC1 pin 1 (B): clean boost signal when regen is CCW
IC3 pin 1: high pitch squel
IC3 pin 7: very distorted signal
IC2 pin 8: flanging signal (it doesn't sound too bad)
IC1 pin 8: low distorted signal
IC1 pin 14: low distorted signal
IC2 pin 6 (C,D): no signal (or very low)
IC2 pin 7 (output): bad distorted signal

4. I know, that's probably the one that stood out most from your readings.
5. I couldn't calibrate BBD using the template from ADA. But I could read of some people who did this by ear (also in the project file from Charlie). I tried this, by carefully trimming T1 and T2. But the signal never came close to anything good.

If you have any suggestions what I should listen for when using an audio prbe (and where to listen) I'm grateful.
Thanks!

[oldschoolanalog]

1. I did calibrate it, as far as I could, according to the project file from Charlie. However, I couldn't calibrate the BBD using the test method from ADA. The scope was unable to read that weak signal.

That's strange. 2V p-p isn't exactly an unreadably small signal for a 'scope.

2. I measured f both from TP and pin 10/11 from 4047. The frequencies from pin 10/11 (35kHz - 2,6MHz) are doubled at the TP. I believe this is correct.

Should read ~35kHz to ~ 1.3MHz at pins 10/11 4047. You are Waaay high w/2.6MHz. Read page 7 of Charlie's pdf.

3. I did audio probe it. But I'm a bit lost here, I don't know what I'm looking for. Here is my result.
IC1 pin 1 (A): clean boost signal
IC1 pin 1 (B): clean boost signal when regen is CCW
IC3 pin 1: high pitch squel
IC3 pin 7: very distorted signal
IC2 pin 8: flanging signal (it doesn't sound too bad)
IC1 pin 8: low distorted signal
IC1 pin 14: low distorted signal
IC2 pin 6 (C,D): no signal (or very low)
IC2 pin 7 (output): bad distorted signal

What happens when the threshold knob is turned to either extreme? Upon a quick glance at the info above & the schematic it seems there is something up w/the "threshold" circuitry. Having flange at IC2/pin8 but nothing "after" that is a hint that things might be amiss there.  Remove the FET; this just takes the threshold/gate (or whatever people are calling it now) out of the circuit.
Proceed from there. (Start over)

4. I know, that's probably the one that stood out most from your readings.

Do the above & see what happens.

5. I couldn't calibrate BBD using the template from ADA. But I could read of some people who did this by ear (also in the project file from Charlie). I tried this, by carefully trimming T1 and T2. But the signal never came close to anything good.

I'm confused here too. If you have a 'scope this should be relatively straightforward. T1 is the bias. Adjust for least distortion. T2 is regen. Adjust to taste.
First set your clock f's correctly. Then remove the FET (if that is the problem it can be dealt w/later). See if you can get it sounding good that way. You do have flange at some points so you are close.

If you have any suggestions what I should listen for when using an audio prbe (and where to listen) I'm grateful.

Do the above first. We'll probe more if needed later.

Thanks!

[BootCut]

I was in a hurry when borrowing the scope at work, I only read the part with 25mV p-p. 2v shouldn't be a problem as you say.

Sorry it was a typo. It's 35kHz - 1,3MHz at pins 10/11 4047 and 70kHz - 2,6Mhz at TP.

I removed the FET and voila! Flanger all over the place! I started to check the schematic and measure on the board only to find out I had the pin configuration wrong. I used an 2N3819 as suggested by bajaman. But it never occured to me to check the pins. I soldered it back on, with twisted leads. And it seems to be working ok. I still need to calibrate T1,T2 and T6 with a scope. I can't get really get it perfect from just turning the trimmers in blindness. But I'm pretty sure this was the only problem, it sounds good.

Big thanks to you oldschoolanalog!

[oldschoolanalog]