Author Topic: Little angel chorus issues  (Read 1096 times)

Unclereaper

Little angel chorus issues
« on: September 04, 2020, 05:46:35 PM »
I built this chorus to spec and the pt2399 gets burning hot and sound dies out and it never choruses.








duck_arse

Re: Little angel chorus issues
« Reply #1 on: September 05, 2020, 12:21:20 PM »
there is a tiny spot of silver on top of your voltage regulator. is that solder splash, or some of the precious bodily fluids of the reg excaping?

voltages. remove the pt2399 from its socket and measure/post the voltages on the socket pins. then reinsert IC and remeasure/post voltages.

Unclereaper

Re: Little angel chorus issues
« Reply #2 on: September 05, 2020, 01:39:19 PM »
Out voltages 1=4.98 2=0.9 but erratic 3 -16 were all zero
In voltages  1=4.98 2=2.43 3=0 4=0 5=4.98 6=0.4 7=0 8=0 9-16 all 2.44
I tried new chip sound passes doesnt chorus then slowly dies out

jfrabat

Re: Little angel chorus issues
« Reply #3 on: September 05, 2020, 02:34:32 PM »
Out voltages 1=4.98 2=0.9 but erratic 3 -16 were all zero
In voltages  1=4.98 2=2.43 3=0 4=0 5=4.98 6=0.4 7=0 8=0 9-16 all 2.44
I tried new chip sound passes doesnt chorus then slowly dies out

I hear you...  It took me 4 builds to get this pedal to work!  First of all, PT2399 are notoriously finicky.  Try grounding it by placing it on a copper board (all pins touching the copper).  Also, I ran into counterfit PT2399 issues, so a reputable source is important. 

anotherjim

Re: Little angel chorus issues
« Reply #4 on: September 05, 2020, 05:01:07 PM »
I think it's locking up. Pin5 should read about 2.5v when the delay chip clock is running.
Some PT2399 don't like the fast clock overdrive that Q2 applies.
Try lifting out one leg of R8 which will isolate Q2. If all else is good, you should have some effect going although not the best chorus sound possible.

Unclereaper

Re: Little angel chorus issues
« Reply #5 on: September 05, 2020, 06:30:55 PM »
No sound at all

frequencycentral

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Re: Little angel chorus issues
« Reply #6 on: September 05, 2020, 07:04:52 PM »
Schematic?

Unclereaper

Re: Little angel chorus issues
« Reply #7 on: September 05, 2020, 07:41:04 PM »
Only one I've found is for an earlier build


EBK

Re: Little angel chorus issues
« Reply #8 on: September 05, 2020, 07:57:32 PM »
It took me 4 builds to get this pedal to work! 
It does sort of feel like we've known you your whole life and watched you grow up building that circuit.   :icon_lol:
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frequencycentral

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Re: Little angel chorus issues
« Reply #9 on: September 06, 2020, 08:50:18 AM »

jfrabat

Re: Little angel chorus issues
« Reply #10 on: September 06, 2020, 09:41:08 AM »
It took me 4 builds to get this pedal to work! 
It does sort of feel like we've known you your whole life and watched you grow up building that circuit.   :icon_lol:

No comment...   ;D ;D ;D

ElectricDruid

Re: Little angel chorus issues
« Reply #11 on: September 06, 2020, 09:53:54 AM »
Out voltages 1=4.98 2=0.9 but erratic 3 -16 were all zero
In voltages  1=4.98 2=2.43 3=0 4=0 5=4.98 6=0.4 7=0 8=0 9-16 all 2.44
I tried new chip sound passes doesnt chorus then slowly dies out

Let's start at the beginning - get the power working. Without the PT2399 in there, you should have:

Pin 1 - 5V, from the regulator. 4.98 looks good to me
Pin 2 - 2.5V reference voltage for the internals. 0.9V is wrong, and suggests to me that the grounding isn't good.
Pin 3 - Ground
Pin 4 - Ground

With the power turned off, you could do a continuity check between your ground points, especially those pins 3 and 4.

Once the power is good, then we can fairly safely put the chip in and see what happens and what voltages we get.

HTH,
Tom
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duck_arse

Re: Little angel chorus issues
« Reply #12 on: September 06, 2020, 10:34:17 AM »
chip-out pin 2 volts should be indeterminate - the pt internals do the dividing. pin 2 chip-in volts at 2V43 looks ok to me.

I think Ben Lyman established that the cap from the LFO to the depth pot is backwards [if polarised] if (+) is towards pot - but that wouldn't kill the effect.

anotherjim

Re: Little angel chorus issues
« Reply #13 on: September 06, 2020, 02:49:01 PM »
Audio (clean/no effect) should get thru no matter what the PT2399 is doing.
If it starts with sound but it fades out, then the input amplifier could be drifting out of bias. There should be 5v on IC1 pin pin3 (coming from 330k R7) and the amp should copy that voltage to its pin1. Check for shorts/track cuts around there.

ElectricDruid

Re: Little angel chorus issues
« Reply #14 on: September 06, 2020, 04:15:33 PM »
chip-out pin 2 volts should be indeterminate - the pt internals do the dividing. pin 2 chip-in volts at 2V43 looks ok to me.

Ack, of course! Sorry! Duck is right. I'm an idiot!

Still, I stand by the rest of it - Check the power and grounds first, and then we move onto the other stuff!
« Last Edit: September 06, 2020, 04:17:36 PM by ElectricDruid »
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Unclereaper

Re: Little angel chorus issues
« Reply #15 on: September 07, 2020, 12:57:41 PM »
Ok I'll try that and which one of you is Ben Lyman because I did business with you and u got me started on pedal building.

Unclereaper

Re: Little angel chorus issues
« Reply #16 on: September 07, 2020, 01:13:48 PM »
Ic1 4.8.  2.9  3.5  0.02  2.1. 2.4.   2.2.  6.7. Ic1 pin 3-4 pass continuity
« Last Edit: September 07, 2020, 01:18:18 PM by Unclereaper »

ElectricDruid

Re: Little angel chorus issues
« Reply #17 on: September 07, 2020, 02:42:12 PM »
Ic1 4.8.  2.9  3.5  0.02  2.1. 2.4.   2.2.  6.7. Ic1 pin 3-4 pass continuity

If 3+4 have continuity, something weird is going on, because you've got different voltage readings for two pins which are supposed to be connected together. Can you check to see what's happening?
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PRR

Re: Little angel chorus issues
« Reply #18 on: September 07, 2020, 02:44:43 PM »
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anotherjim

Re: Little angel chorus issues
« Reply #19 on: September 07, 2020, 05:22:04 PM »
Ic1 4.8.  2.9  3.5  0.02  2.1. 2.4.   2.2.  6.7. Ic1 pin 3-4 pass continuity

If 3+4 have continuity, something weird is going on, because you've got different voltage readings for two pins which are supposed to be connected together. Can you check to see what's happening?
I think IC1 is the dual opamp Tom.
Pin8 6.7v shows a weak battery.
I wonder if the power supply is just fading under load?
IC1 pin3 should read closer to the 5v output from Q2 which is also pin1 of the PT2399. Pin1 should have 5v.
Is the PT2399 still out of the board?