Aquaboy Delux 2013 - no wet signal

[medeiros68]

Howdy folks,
seems to be a common problem, I did go through some of the posts to get some help before bugging everyone, but this is what I am facing - no delay signal out of a ABDX 2013. First off, it was working, indeed, it has been forking for the last 2 years.

Here's the info:
(1) Project Name: ABDX 2013, I am unsing 2 MN3205 and the associated clock MN3102; I did set the voltage properly, and it is around 8.84V. At the compander I set R13 and R14 with 10k each. Forst time I built I used to test all my MN3008, so I socketed R13 & R14.

(2) General description of the problem:
No wet signal, only dry signal through
(3) Steps that you have taken to try to resolve the issue:
a) first I followed the troubleshooting in the manual:
Feedback 1/2, Mix 1/2, Delay max.
- checked the signal at pin7 of the compander (check -ok)
- pin 7 at IC3 (BBD) to confirm BBD was receiving the signal (check - ok)
Since I had had it working before, I had set it properly the jumpers.

This is what else I did:
- checked the signal at the output of LF353 - (pin1) - Check, ok
- checked the signal at the pin 5 of the compander - check, ok
- followed the delayed signal through the 2 BBDs - check, ok. I adjusted again the bias to make sure no distortion was going through, as well as the cancelling pot to reduce clock noise.
- checked the signals at pins 14/15 of the compander - check, ok.
- checked the signals at pins 10/11 of the compander - NO SIGNAL.

So at that point I concluded that the problem would be with the compander I am using, a SA571 Phillips made in Thailand.


(4) List any substitutions you used for parts/values

I had a stash of companders, and started replacing one at a time. Once I reached my 6th compander, I started wondering whether there wouldn't be something else.

I then checked T1 which sets the levels for mixing and feedback, and let it half way. I did check it in full CW and full CCW.

I concluded that the BBDs are working and the delay in the signal has been produced. Along the signal path, the signal disappears at the output of the compander (pins 10/11), and therefore the compander must be shot.

I changed companders, and maybe I got a bad batch, because none worked.

My questions to the forum:

Did I miss anything?
Is it common to have bad companders?
I checked mouser and digikey - DIP companders are obsolete. Where can I get some? Small Bear does not have them.

Thanks all for your time reading.
best
gilberto

[madbean]

Excellent work on your debugging attempt. Here are a couple of possibilities:
pin10 and 11 are getting grounded somehow and therefore no signal going out.
R37 is the wrong value.

To do:
- check soldering, look for any solder bridges around those pins.
- if you have a continuity checker, verify that C30 is connected to pins10, 11 and that none of them have continuity with ground
- compare your compander voltages with the ones in the latest Aquaboy project (should be close to the same) http://www.madbeanpedals.com/projects/Aquaboy/Aquaboy.pdf
- verify you have a 20k in R37

If everything checks out, then try this - remove R37 or clip one of the leads.

These are all the steps I would take before trying to get a different chip. Let us know what happens.

[Scruffie]

Just to say if bean's suggestions don't work out, Smallbear does have companders, the v571D works nicely

[gordo]

For a guy with 14 posts that's some really impressive documentation of troubleshooting. Well done. Hope you find the problem!

[medeiros68]

Dear all,
thanks for the superfast reply, and kind words (Madbean, Scruffie and Gordo).
Indeed, to be respectful with everyone's time I take pride in providing precise info, hoping that it can benefit others and also it is a small price to pay to drink from this well of knowledge.

Thanks Madbean - much obliged for the detailed step by step.

Here are my results:

1) checked signal path between pins 10/11 through the 1uF cap (C30). I removed the compander and measured the capacitance between the pin 10/11 at the socket, and pin 3 of the Mix knob. Got 1uF, so there's continuity. No leaks to GND.
2) measured all voltages, comparing them with the new version.
All on the dot, except on pins 10,11,12, of the compander which I reproduce below (Vc=9.23V, so it is pretty close to the Vc=9.4V):
pin 10 = 1.33V (should've been 3.10V)
pin 11 = 1.33V (should've been 3.10V)
pin 12 = 5.42V (should've been 1.84V)

3) removed R37, and the same voltages as reported earlier remained.

4) I also checked whether there was continuity between the feedback and mix pots, so since they are in parallel, when measuring form pin 3 (either one of course) to ground I had 25k, which is what one would expect.

So I guess the compander is no longer working. I will keep trying every single one I have.

About V571 - thanks for the plug, Scruffie. I checked their data sheet and it is a copy and paste version... min voltage of 6V, and max 18 V, so looks like I am game and it is a drop in replacement. If all else fails, I'll do that.

Anyone has experience in describing its performance? Coolaudio has a license, or just bought the mask set for making the chips? In other words, anyone knows if they redesigned the chip to comply with more modern process, yet retaining the same sonic characteristics?

Again thanks everyone for the support. My wishes of a enjoyable Sunday to all,
best,
gilberto

[medeiros68]

Folks,
magically the problem disappeared.
I plugged in the guitar one last time, a couple of days later, just to hear the always nice Aquaboy repeats....

I wonder if this could be related to some type of residual charge in C30, thus changing all biasing in the compander.
Next time this happens I will try to short it (C30).

best

[madbean]

Well that's very strange. But, at least it is working now.