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 Forum index » DIY Hardware and Software » Jürgen Haible designs
Triple Chorus troubleshooting
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gs3333



Joined: Feb 04, 2010
Posts: 8
Location: UK

PostPosted: Sun Sep 23, 2012 7:11 am    Post subject: Triple Chorus troubleshooting Reply with quote  Mark this post and the followings unread

Hi guys

First off, it's a long time since I've logged onto this forum and it's very sad to hear of Jürgen's death. He was always very helpful and generous with his time when I emailed him in the past.

I have a problem with a triple chorus I've built which simply doesn't function. I suspect the oscillators aren't functioning correctly. Would anyone mind marking the points on the board overlay where I can test the outputs of the oscillators? http://www.jhaible.de/triple_chorus/jh_triple_chorus_overlay_tiny.jpg

Thanks in advance

gs
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zthee



Joined: Feb 20, 2008
Posts: 413
Location: Stockholm

PostPosted: Mon Sep 24, 2012 6:12 am    Post subject: Reply with quote  Mark this post and the followings unread

Pin 1 and 4 of the TDA1022 should see a square wave.

Do you have signal at the BBD-drive output? Junction of R6 and C4. If not, then there is something wrong with the input part.

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Serenadi



Joined: Jul 03, 2007
Posts: 89
Location: Germany

PostPosted: Mon Sep 24, 2012 8:56 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi gs,

I've had a strange problem with the oscillators back in 2008 discussed with Jürgen.
Maybe you run into the same issues.
Please read this and the following posts:
http://electro-music.com/radio/forum/post-198703.html#198703

Good luck.

Bernd
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gs3333



Joined: Feb 04, 2010
Posts: 8
Location: UK

PostPosted: Thu Sep 27, 2012 2:47 pm    Post subject: Reply with quote  Mark this post and the followings unread

Thanks guys. I'll run some tests when I get a chance and get back to you with the results.
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jumunius



Joined: Apr 19, 2010
Posts: 346
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Audio files: 13

PostPosted: Fri Sep 28, 2012 10:10 pm    Post subject: Reply with quote  Mark this post and the followings unread

Could also just be bad TDA1022s. I had a problem with at least one of mine initially.
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The Bad Producer



Joined: Mar 08, 2009
Posts: 255
Location: The Manhole

PostPosted: Thu Oct 04, 2012 3:36 pm    Post subject: Reply with quote  Mark this post and the followings unread

I think (so long ago Laughing ) I had a problem like this which was from using a particular type/brand of 4011, IIRC it was maybe HEF vs. CD, but not sure, I think I asked JH at the time, it's probably buried in the thread somewhere...

hahaha, not much help, sorry!

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gs3333



Joined: Feb 04, 2010
Posts: 8
Location: UK

PostPosted: Sat Oct 06, 2012 8:16 am    Post subject: Reply with quote  Mark this post and the followings unread

It appears to be a fault with the input section.

As I suspected, I have no signal at the junction of R6 and C4 (pin 7 of U5).

I've checked the board thoroughly and can't see any obvious errors with component values, polarity, etc.

It could be relevant that I have -15V at pin 4 of U6-9 but only -14.7V at pin 4 of U1-5 for some reason.

I appear to have a (relatively) stable -7.35V from pin 7 of U2-4. -5.28V from pin 7 of U5.

All help very gratefully received!
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elmegil



Joined: Mar 20, 2012
Posts: 1486
Location: Chicago
Audio files: 14

PostPosted: Sat Oct 06, 2012 9:45 am    Post subject: Reply with quote  Mark this post and the followings unread

I just finally got a Blacet Time Machine working after similar sorts of things.

I had an audio signal all the way up to the bucket brigade chip, and nothing on its output but clock noise. All the voltages and the clocks for the chip looked perfect.

Then I noticed that the socket (a relatively cheap one, and no criticism to the owner of this board, mine on hand are all the same type) had gotten bent and there was little to no connection between two of the key power pins and the socket (which was where I had been measuring the voltages to say they were OK).

I replaced the socket, adjusted the bias appropriately, and voila, we now have a working module.

I've had this type of issue bite me at least once previously as well.

So--if all the voltages look right, and all the signals look right, you might make sure your sockets are actually making contact with your chips as you expect....
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jumunius



Joined: Apr 19, 2010
Posts: 346
Location: San Francisco, CA
Audio files: 13

PostPosted: Sun Oct 07, 2012 12:18 am    Post subject: Reply with quote  Mark this post and the followings unread

gs3333 wrote:
It could be relevant that I have -15V at pin 4 of U6-9 but only -14.7V at pin 4 of U1-5 for some reason.


Look at the power schematic again. Some of those pins use "V1" and others use "V2" -- they are different values. I remember that tripped me up too at some point as well. Your readings sound correct.

Pay special attention to your EQ switches and wiring. You don't have signal at IC5 pin 7, and arguably the most fallible part of your signal path up til this point are the 5 wires associated with the Mode pads. Did you wire your switches right, is the soldering good, if you use headers is your crimping good, etc.

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gs3333



Joined: Feb 04, 2010
Posts: 8
Location: UK

PostPosted: Wed Oct 10, 2012 9:11 am    Post subject: Reply with quote  Mark this post and the followings unread

I've been back and checked power supply voltages. All looks right to me.

-V1: -15V
-V2: -14.7V
-V3: -7.35V
-V4: -5.28V

I've used turned pin IC sockets throughout this board. No apparent problems there.

My wiring to the mode switch, mod and bypass switches all looks correct. Testing for continuity from the board back to the board, everything checks out.

I have spare LM1458s and a TL071 which I can swap in for U1-5 to try and rule them out.

Any other suggestions gratefully received.
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gs3333



Joined: Feb 04, 2010
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Location: UK

PostPosted: Thu Oct 11, 2012 7:06 am    Post subject: Reply with quote  Mark this post and the followings unread

U1-5 swapped. No change.
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gs3333



Joined: Feb 04, 2010
Posts: 8
Location: UK

PostPosted: Mon Oct 29, 2012 2:52 pm    Post subject: Reply with quote  Mark this post and the followings unread

I'm at a loss with this one. Any more suggestions before I tear it apart and try again?

All help very much appreciated.
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Serenadi



Joined: Jul 03, 2007
Posts: 89
Location: Germany

PostPosted: Wed Oct 31, 2012 10:04 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi gs3333,

you wrote you got no signal at pin 7 of U5B.
So I suppose you have a scope or a signal tracer available. Scope is recommended.

Please check every single power supply of the OPamps
- pin 7 of U1 (0V)
- pin 3 of U1 (-7,3V)
- pin 4 of U1 (-14,7V)
- pin 8 of U5 (0V)
- pin 4 of U5 (-14,7V)
- pin 5 of U5 (-5,3V)

Please feed your input with a known signal and check these points in the following order:
- Pin6 of U1 (note! this is a single Opamp) - should be nearly the double amplitude of input signal
- The right pin of "dry" connector (should be nearly the same)

in the "Linear" position of the mode switch you should also see the signal at
- the junction of R65 and C61 (the base of the mode switch)
- the junction of R7 and C4 (the input of U5B)
- pin 7 of U5B

this is the direct way of the signal between input and "BBD_Drive" (U5B).

Please respond.

Bernd
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gs3333



Joined: Feb 04, 2010
Posts: 8
Location: UK

PostPosted: Wed Oct 31, 2012 10:57 am    Post subject: Reply with quote  Mark this post and the followings unread

Bernd, thank you so much.

I'll give this a try (hopefully before the weekend) and let you know the results.

Thanks

Greg
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gs3333



Joined: Feb 04, 2010
Posts: 8
Location: UK

PostPosted: Tue Dec 04, 2012 7:46 am    Post subject: Reply with quote  Mark this post and the followings unread

Measurements as follows:

All power supply voltages correct.

Feeding a 7.5V peak-to-peak sine wave into the input, I get the following:

Pin 6 of U1: 10.7V p-p

Pin 7 of U5: 3.5V p-p

Dry output: ~10V p-p


Any suggestions? Thanks.
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Serenadi



Joined: Jul 03, 2007
Posts: 89
Location: Germany

PostPosted: Sun Dec 09, 2012 1:42 pm    Post subject: Reply with quote  Mark this post and the followings unread

First ...
gs3333 wrote:
It appears to be a fault with the input section.
As I suspected, I have no signal at the junction of R6 and C4 (pin 7 of U5).

... and then
gs3333 wrote:
Pin 7 of U5: 3.5V p-p


So there seems to be no problem with the input section. Good.
Knowing the direct way is correct, you might check also the input filters pin 7, U2b, respectively position "Solina" on mode switch and also pin 7 of U4b resp. position "EQ". But this alongside, it has nothing to do with the main functionality.

Ok, pin 7 of U5 is labeled "BB_Drive", which means its the input of the delay chips U10, U12 and U14. Leaving the mode switch in "linear" position, please check:

- signal at input pins 5 of U10, U12 and U14 (should be always a little lower than pin7 of U5).

- If you got signal there, check the outputs of the BBD chips U10,12 and 14: pin 8 (& pin 12).

- If you have input signal but no output, you have to check the clock signals driving the BBD stages.
These are pins 1 and 4 of all three BBDs. These are high frequency signals, around 50kHz afair.

So far, please let me know your results.

Bernd
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