"Little Angel" - Super Simple PT2399 Mini Chorus

[Pakaloabob]

Thanks, Rob.
At least I know I'm not completely crazy if it happens to someone else.
Another funny thing I noticed is that I can play with it running off a battery, change to a power supply and get no modulation, then remove the power suppply and reattach battery and still get no effect for a little while. If I leave it for a few minutes it will work fine on the battery!
Is it possible that the LFO somehow latches until the proper voltage is applied?
Like I said in an earlier post, for some reason my power supply does not provide 9 volts when attached to the Little Angel circuit, but a battery does. Since the PT2399 voltage is regulated, only the dual-opamp would be affected by this voltage drop. Which is why I think the LFO is the issue.
I wish I had another power supply to test with. I was planning on building the AMZ power supply. Maybe this will be the motivation I need.

[nick d]

              This is driving me crazy - if anyone can help , I would appreciate it immensely.
               I'm using Ricks schematic Version 2 updated 11/08/10 , all components stock .
               The vero layout is from Harald Sabro Bolstad , posted on this forum by ( I think ) Rick .
               I have altered the layout only slightly , to avoid any jumpers running under ICs .
               I've checked for shorts throughout , and for continuity everywhere I can see .
               The test results are :-
                                               By-passed - normal output
                                               Effect - sounds normal , perhaps a tiny volume drop
                                               Audio probe - as effect on pin 1 opamp then the same at pin 15 PT2399 , no sound anywhere else on this IC . A gentle thumping sound from pin 7 on the
                                                opamp , varying with speed pot - I guess this means the opamp works .
                                               
                                              Voltages -
                                                              IC 1  1) 5.21 V     
                                                                      2) 4.87 V
                                                                      3)  4.77 V
                                                                      4)   0.00 V
                                                                      5)  varying 2.5 - 3.5 V
                                                                      6)       "     2.5 - 3.5 V
                                                                       7)      "     1.4 - 7.8 V
                                                                        8.56 V (normal output of my PSU ) 
                                                                       

                                                             IC2     1) 5.01 V
                                                                       2) varying 2.49 - 2.54 V
                                                                       3) 0.00 V
                                                                       4)0.00 V
                                                                       5)  5.01 V 
                                                                       6)  as pin 2
                                                                       7 +   0.001 V
                                                                       9 - 16) all as pin 2 , i.e.minor variation around 2.5 V

                                 Also , I pulled the 2399 from another pedal that was already working , thinking that the new one was a duffer - no change .
                                 
                                 I know the answer must be right in front of me , but I'll be damned if I can see it - HELP !!!!!!!!!!!!!                                 

[frequencycentral]

My first guess with vero would always be microscopic continuity on the cut tracks - check it out with a continuity probe.

[nick d]

                      Already done that (several times ) but I'll do it a few times more . I was hoping something in the voltages might give us a pointer - the fact that I get a signal on pin 15 but nowhere else makes me think the fault is in that area - I'll keep on digging !

[nick d]

                 RESULT!!!!!!
                   The 100R from pin 6 to ground was OC at the ground end - it was the last one in the drawer and had been cut short previously , so I missed it , hidden between 2 other wires .
                   
                   Anyway , it now works - and might I say how lovely it sounds !
                   Thanks , Rick - you're a genteman and a scholar , as we used to say !

[Govmnt_Lacky]

OK, I built this Lil' Angel on PCB for a 1590A. Only wired it for wall wart power from DC jack. I get bypass no problem, when I engage the circuit, it seems like the depth pot does not work at all (no change in modulation) however, the speed pot seems to do something when I crank it between 80-100%. I get a subtle vibrato effect. I used 100KB for both pots. Here are some voltages.

Opamp (5532)
Pin1) cycles on and off from 0V to ~1.4V (This looks wrong)
Pin2) 2.8-3.2V
Pin3) 2.8-3.2V
Pin4) 0
Pin5) 4.75V
Pin6) 4.9V
Pin7) 5.2V
Pin8) 9.18V

2399
Pin1) 5V
Pin2) 2.4-2.5V
Pin3) 0
Pin4) 0
Pin5) 2.6V
Pin6 - Pin8) 0.7V
Pin9 - Pin16) 2.4-2.5V

Voltage converter seems to work correctly.

Any help is appreciated. Thanks.

[nick d]

                  I've just got this going , having got stuck and posted the voltage readings .
                  Looks like you're using pins 3-2-1 for LFO - your readings tally with mine except for pin 1 , which looks very low .
                    Could be a low-value resistor shorted to ground - I see a 4k7 in that area - try looking around there .

[Govmnt_Lacky]

OK, I built this Lil' Angel on PCB for a 1590A. Only wired it for wall wart power from DC jack. I get bypass no problem, when I engage the circuit, it seems like the depth pot does not work at all (no change in modulation) however, the speed pot seems to do something when I crank it between 80-100%. I get a subtle vibrato effect. I used 100KB for both pots. Here are some voltages.

Opamp (5532)
Pin1) cycles on and off from 0V to ~1.4V (This looks wrong)
Pin2) 2.8-3.2V
Pin3) 2.8-3.2V
Pin4) 0
Pin5) 4.75V
Pin6) 4.9V
Pin7) 5.2V
Pin8) 9.18V

2399
Pin1) 5V
Pin2) 2.4-2.5V
Pin3) 0
Pin4) 0
Pin5) 2.6V
Pin6 - Pin8) 0.7V
Pin9 - Pin16) 2.4-2.5V

Voltage converter seems to work correctly.

Any help is appreciated. Thanks.

Gonna triple check for solder bridges and component values today. Then, hook this up to a DC power supply and post new voltages.

Stand by... 

[Govmnt_Lacky]

Ok... Some things to note about my build.
I used 100KB pots for both Speed and Depth.
I wired the Speed pot backwards (I used lugs 1 & 2 so when I go full CCW I get max speed)

New voltages (I think)

NE5532 (swapped out a new one)
Pin1) 2.7-3.2V (ONLY when Speed pot is at 0-20% rotation. Above 20% rotation, it is 0-1.4V)
Pin2) 2.7-3.2V
Pin3) 2.7-3.2V
Pin4) 0
Pin5) 4.7V
Pin6) 4.8V
Pin7) 5V
Pin8) 9V

2399
Pin1) 5V
Pin2) 2.45V
Pin3) 0
Pin4) 0
Pin5) 2.5V (DOES NOT LOOK RIGHT COMPARED TO nickd POST. SHOULDN'T IT BE 5V?)
Pin6) 0.7V (THIS LOOKS WRONG!)
Pin7) 0.7V
Pin8) 0.7V
Pin9-16) 2.5V

Voltage converter is good.

Checked for values and solder bridges. None to be found.

Things that look suspect to me are Pin 1 of the opamp and its relation to the Speed pot. Also, Pin 5 and Pin 6 of the PT2399.

Any help is appreciated. THANKS!

[nick d]

            Just checked my voltages on the working version - your 2399 is pretty well the same as mine , but your pin 1 ( my pin 7 ) is still off .
            Must be somewhere around the LFO ( only my humble noob guesswork ) . Keep on digging - its in there somewhere !

[nick d]

   The voltages I posted were for the non-working version . My pin 5 now shows 2.5 V , so all your 2399 voltages look OK . Still looks like the LFO area is the prime suspect .
    Where's Rick when we need him !   ( only joking ! )

[Govmnt_Lacky]

   The voltages I posted were for the non-working version . My pin 5 now shows 2.5 V , so all your 2399 voltages look OK . Still looks like the LFO area is the prime suspect .
    Where's Rick when we need him !   ( only joking ! )

Do you still get the voltage change (2.5-3.5V) on Pin 6 of the 2399 like in your original post?

[Govmnt_Lacky]

Wired up the Speed pot correctly (Lugs 2 & 3) and I still get the same outcome. Seems like I only get voltage wobble on Pin 1 of my 5532 if the Speed pot is at 80-100% of the pot rotation. Below 80% and the voltage lays at 0 and intermittently peak to ~1.5V! 

Also, I still only get 0.7V on Pin 6 of the 2399. Is that correct?

I read in past pages of this thread that some people have found that the 5532 only likes a 470K pot for Speed. Should I try a TL072 as the LFO?

Please help 

[nick d]

    Just done a run-thro on my voltages .
                       PT2399
                                     1) 5.02 V
                                      2) 2.5 slight wobble
                                      3) 0V
                                      4) 0 V
                                      5)  2.22 - 2.5 V   (didn,t spot the small variation before )
                                       6)  0.75 V
                                       7)0.66 V
                                        0.66 V
                                        9 - 16) As before

                       NE 5532   
                                           The only significant difference is pin 1 ( opamp LFO output - pin 7 on my layout )
                                              I have a varition from 1.4 - 7.4 ( lo-speed ) to 2.5 - 3.5 ( hi-speed )

                             

                                            Hope thats clarified the picture - that LFO voltage still looks way off , or is that a red herring ?
                                            Stick at it , you'll get there .

[Govmnt_Lacky]

                       NE 5532   
                                           The only significant difference is pin 1 ( opamp LFO output - pin 7 on my layout )
                                              I have a varition from 1.4 - 7.4 ( lo-speed ) to 2.5 - 3.5 ( hi-speed )

Did you use the 470K for the Speed pot?

[Govmnt_Lacky]

Used a DMM to check for solder bridges over ENTIRE circuit - NONE
Checked ALL component values against layout - ALL good except for using 100KB pot for Speed.
Swapped ICs - swapped both AND installed a TL072 for LFO.... no change.

Still getting the strange voltages on Pin 1 of the LFO. With the Speed pot set between 0-80%, I get intermittent voltages ranging from 0V to 1.5V (Sometimes I see larger values however, my DMM on "flashes" them and I can hardly read them fast enough.
When the Speed pot is set to 80-100%, I get a solid voltage swing from ~2.5 to 3.5V.

According to nick_d's input, when the Speed pot is CCW, I should get a solid voltage swing between ~1.4 to 7.4V.

Getting desperate 

[nick d]

                  Looking at the speed pot on the schemo - you say 2.5 - 3.5 V at hi-speed , the lower end of the range seems to be where it goes wrong .
                  The unused pot connection - is it left open or tied to the wiper ? I tied mine to the wiper , after reading "The Secret Life of Pots ".

[jable1066]

I am having the exact same problem! I'm getting all the voltages you are getting... I've done all the solder bridge checks, component values, wiring, orientation etc etc and I'm stumped if I know the answer. My voltages sway like yours do as well...

[Govmnt_Lacky]

The unused pot connection - is it left open or tied to the wiper ? I tied mine to the wiper , after reading "The Secret Life of Pots ".

I left it open (Lug 1). I will try tying it to the wiper and report back the results. Cross your fingers please  

EDIT: I am out of 100KB 9mm pots so I am going to have to use 100KA pots. I hope they work!!

[jable1066]

Mine was also left open...