Man O' War DX - Calibration

[benny_profane]

(1) Project: Man O' War DX powered by OneSpot 12V supply (actual reading: 11.73V)

(2) Issue: Unable to successfully calibrate. I'm stuck on biasing the first MN3005. I get a signal at pin 7 of IC3, however the signal at pins 3 and 4 of IC3 have a high-pitched whine mixed in and rather than getting a delay, the signal repeats and ramps up to a high-pitched oscillation.

I'm getting a very high-pitched, amplified signal mixed with the dry signal at pin 7 of IC2a.

Voltage at pin 1 of IC2 is around 1.2V (build doc has 0.88V) all other voltages before the first BBD are in spec.

(3) Steps to resolve issue: I probed the signal path from the input and confirmed part values. The dry signal gets to IC2 without anything remarkable. Reflowed joints. Removed Q2 and Q3 (NPN Si) and put in sockets. Originally had 2n5088 devices in each spot, same issue and voltages when replaced with 2n3904 devices.

(4) Substitutions: Feedback pot is 25kB instead of 20kB. MN3005 sourced from CabinTech; V571 from SBE.

Pictures attached. IC5 has been removed for calibration purposes.

[tcpoint]

There was a AD-900 with MN3008 build doc awhile ago on freestompboxes.org.  It's, obviously, more complicated than the MN3005 version but still a good read.  It assumes an oscilloscope.  It still helps to visualize what the signal should look like, even when using an audio probe.

Here's the doc:  https://drive.google.com/file/d/1MME5E1GFaOBb-6xN6fMEdc4ghryU8rEh/view

[benny_profane]

There was a AD-900 with MN3008 build doc awhile ago on freestompboxes.org.  It's, obviously, more complicated than the MN3005 version but still a good read.  It assumes an oscilloscope.  It still helps to visualize what the signal should look like, even when using an audio probe.

Here's the doc:  https://drive.google.com/file/d/1MME5E1GFaOBb-6xN6fMEdc4ghryU8rEh/view

Thanks, I'll have to give that a look. I'm hoping to get an oscilloscope in the future, but I don't have one yet.

I haven't made a project with this compressor IC before, so I'm a little unsure about how to diagnose issues with it. It seems like that is the place to start, but I'm really at a loss.

[benny_profane]

There was a AD-900 with MN3008 build doc awhile ago on freestompboxes.org.  It's, obviously, more complicated than the MN3005 version but still a good read.  It assumes an oscilloscope.  It still helps to visualize what the signal should look like, even when using an audio probe.

Here's the doc:  https://drive.google.com/file/d/1MME5E1GFaOBb-6xN6fMEdc4ghryU8rEh/view

Thanks, I'll have to give that a look. I'm hoping to get an oscilloscope in the future, but I don't have one yet.

I haven't made a project with this compressor IC before, so I'm a little unsure about how to diagnose issues with it. It seems like that is the place to start, but I'm really at a loss.

I read through the document, and I don't think I'll be able to use much of that calibration procedure since it does rely so heavily on an oscilloscope.

Could this be caused by an issue with the V571? The output from that IC has the high-pitched signal (so it's not clock noise).

[tcpoint]

I've had more trouble with companders than BBDs.  Here's a couple of articles of interest.

https://electricdruid.net/noise-reduction-with-companders/
https://www.experimentalistsanonymous.com/diy/Datasheets/SA571%20AN.pdf

Did you take out IC3 and test the signal at pin 7?  Actually, testing the emitter on Q2 would be a better test.

[benny_profane]

I've had more trouble with companders than BBDs.  Here's a couple of articles of interest.

https://electricdruid.net/noise-reduction-with-companders/
https://www.experimentalistsanonymous.com/diy/Datasheets/SA571%20AN.pdf

Did you take out IC3 and test the signal at pin 7?  Actually, testing the emitter on Q2 would be a better test.

I just took IC3 out and tested the signal at pin7 of the compander as well as the emitter of Q2. The high-pitch signal isn't there, but there is a low hum now. It's introduced at Q1 (2n5088), and is there with the signal up to the output of the compander.

[benny_profane]

I replaced Q1 (previously a 2n5088) with a 2n3904. The signal now passes fine up until the compander. At pin 7, there's a high-pitched signal with the dry signal very faintly present. The emitter of Q2 is the same.

I think I'm going to try swapping the compander. This seems to be the root of the issue.

[HamSandwich]

What's your feedback set at? Your description sound like run away oscillation.

[benny_profane]

What's your feedback set at? Your description sound like run away oscillation.

Per the calibration instructions, the feedback, mix, rate, and depth knobs are at min. Delay is at 12 o'clock.

This is all happening at the compander it seems. The signal is fine going in, then turns to a high-pitch whine at the output. All voltages are okay for the compander except for pin 1, which is close to twice as much as what's specified in the doc (i.e., ~1.5v rather than 0.88v).

[HamSandwich]

The first half of the compander chip is being fed with return of the loop of the feedback as well, so I'm not wholly convinced it's impossible for it to be something further down the line.

Does twiddling any of the knobs cause changes in the noise?

It would be great to check another commander chip, but you could try someone radical. Take the chip out, stuff a makeshift jumper from a resistor lead and jumper pins 6 and 7 together and also 14 and 11 together. I think that should remove the compander from the equation and allow you to get signal through. Feedback might be wonky, but if that isn't really the case, turning it all the way down should negate it.

Hope that doesn't blow up your MN's 

[benny_profane]

The first half of the compander chip is being fed with return of the loop of the feedback as well, so I'm not wholly convinced it's impossible for it to be something further down the line.

Does twiddling any of the knobs cause changes in the noise?

It would be great to check another commander chip, but you could try someone radical. Take the chip out, stuff a makeshift jumper from a resistor lead and jumper pins 6 and 7 together and also 14 and 11 together. I think that should remove the compander from the equation and allow you to get signal through. Feedback might be wonky, but if that isn't really the case, turning it all the way down should negate it.

Hope that doesn't blow up your MN's 

I have some replacement compander devices coming in to try out. I'm going to do a full verification of the circuit again to see if I've missed anything in the meantime. I'll give your suggestion a try as well.

If any eagle-eye folks out there want to play from home, I'd really appreciate the extra eyes on this.

[Jules]

I too am having problems calibrating my MOW Dlx.
In saying that I have never successfully built and calibrated an analog delay.
Have tried Aquaboy, total recall and MAW dlx and have not been able to calibrate and get any of them to work.
I have built every other complicated build with success (polychorus, infinitephase, Ada flanger etc.)
Why I can't build an analog delay successfully has got me beat (I don't have access to an oscilloscope either)
Anyway I will keep watching this thread and start troubleshooting my Man o war dlx build as well. Good luck with yours!

[benny_profane]

Update: Swapped the compander with a new device. Although I was hoping it'd be that easy, the behavior is the same as before.

I'm thinking that some of the slight voltage drifts are more important than I originally thought. I'm going to reverify my components and provide a comprehensive list of voltages.

[benny_profane]

Power Supply: OneSpot – 11.82v

Transistors   
Q1   Si NPN (2n3904)
C   11.53
B   4.49
E   4.04
   
Q2   Si NPN (2n3904)
C   11.54
B   2.81
E   2.19
   
Q3   Si NPN (2n3904)
C   11.54
B   4.4
E   3.78
   
Q4   Si NPN (2n5088)
C   11.54
B   3.75
E   3.16
   
Q5   2n5088
C   0.511
B   0.511
E   0
   
Q6   2n5088
C   7.35      (Drains when probed)
B   0.521
E   0
   
Q7   2n5087
C   8.37
B   11.39
E   11.55

Integrated Circuits
IC1   4558
1   5.71
2   5.71
3   5.7
4   0
5   5.7
6   5.72
7   5.72
8   11.56
   
IC2   NE570
1   1.07
2   1.85
3   1.85
4   0
5   1.85
6   1.85
7   2.84
8   1.85
9   1.85
10   4.4
11   4.4
12   1.85
13   11.56
14   1.85
15   1.85
16   0.98
   
IC3   MN3005
1   11.56
2   5.47
3   4.72
4   4.71
5   0
6   5.47
7   5.65
8   0.73

IC4   MN3101
1   10.9
2   5.47
3   0
4   5.47
5   10.85
6   0.945
7   0
8   0.727
   
IC5   MN3005
1   11.56
2   5.49
3   4.48
4   4.48
5   0
6   5.49
7   5.57
8   0.734
   
IC6   MN3101
1   10.93
2   5.48
3   0
4   5.49
5   10.88
6   0.935
7   8
8   0.734

[madbean]

These voltages look pretty good to me. There some variation but that's not unexpected.

What about your MN3101? Where did those come from?
Do you have a frequency measurement option on your multimeter? It might help if we can verify the range of you clock frequencies across the min and max delay times.

It's not that unusual to hear a bit of clock frequency in the BBD depending on where the clock trimmers are set, but given that there is no delay output at all the problem must reside in either the BBDs or the MN3101.