# Pitch witch modulation circuit



## susie_1987 (Oct 26, 2020)

I checked the whole pcb and everything is where it should be. The lfo circuit works when I flash a flashlight at it, but it seems the led inside cannot produce enough light to make the pitch change enough. With the led inside alone, I only hear minor chorusing, but in demos the depth seems to be much greater. Could it be my ldr? Below are its values. I used the 1 meg one. Thanks in advance!


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## zgrav (Oct 26, 2020)

your ldr has nothing to do with how bright or dim your LED flashes.  the circuit responds to your flashlight so your LDR is probably OK.  what voltages are you getting on the pins for the 4558 IC?


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## susie_1987 (Oct 31, 2020)

I know the ldr has nothing to do with how bright it flashes, but couldn't it be possible if the resistance is too high when illuminated, the the type of ldr could affect the behavior. I get a light chorus and not much else. 
For Pt2399
1. 4.9
2 2.469
3 0
4 0
5 2.81
6 2.469
7 0.6
8 0.664
9 2.468
10 2.469
11 2.47
12 2.469
13 2.469
14 2.469
15 2.47
16. 2.47

Lm-386n-1
1 1.298
2 0
3 0
4 0
5 4.31
6 8.83
7 4.45
8 1.3

Jrc 4558d
1) cant tell because it's oscillating too quick for me to read
2) 4.41
3) 4.41
4) 0
5) oscillating cant read
6) 4.41
7) oscillating
8) 8.83

3 pin transistor
1) 4.9
2) 0
3) 8.83


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## susie_1987 (Oct 31, 2020)

Thank you for the help btw


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## zgrav (Oct 31, 2020)

You voltages on your ICs show you have something close to 9 volts and a reference voltage of about half that on your some pins, which seems OK.  How much range in the effect do you hear when you use your flashlight in a dark room?  That should be close to the effect you get from using your LED.  What does your LED look like when the power is on?  Does it get bright or does it stay dim?


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## susie_1987 (Nov 1, 2020)

Thank you for the response I really appreciate the help. When I do the flashlight in the dark it sounds like it should. However, when the led is flashing on its own it hardly does a chorus sound. The led pulses and behaves like it should according to the waveform. I'm not sure why it takes so much light for the modulation circuit to work right.


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