Fuzz Dog Cherub - No Chorus

[Fazzer]

Hi,

I'm in a world of pain with this one. I get sound out but with no chorus and I think the sound is low level as well. I took the pt2399 out and still heard the same sound coming out so the audio is just bouncing around the resistors and caps. Audio probing seams to have low level signal everywhere. Signal coming in is nice and strong but everywhere else is low level.

http://pedalparts.co.uk/docs/Cherub.pdf

input voltage 8.23

pt2399
1 4.91
2. 4.92
3. 0
4. 0
5. 0 then jumps to 4.93 then jumps back to 0
6. 0.72
7. 0
8. 4.53
9. 4.6 to 4.9 wobbles
10.  4.86
11. 4.86
12. 4.85
13. 4.83
14. 4.6 to 4.9 slowly increases
15. 4.91
16. 4.91


NE5532P
1. 4.04
2. 3.6
3. 2.87
4.0
5. 2.14 to 3.64 wobbles
6. 2.6 to 2.7 wobbles
7. 2.1 to 3.6 wobbles
8. 7.82

78L05

I 7.83
G 0
O 4.92

2N3904
C 0.1
B 0.69
E 0

1N4148

IV 4.91
FV 0.69

don't know where to start with this one?

Cheers

Fazzer

[slacker]

Something's wrong round pin 2 of the PT2399, it should be around 2.5 Volts, this then sets the voltage on pins 9 to 16 which should also be about 2.5 Volts. Check that you haven't got a blob of solder or stray component lead causing a short between pins 1 and 2 of the PT2399.

[ElectricDruid]

Something's wrong round pin 2 of the PT2399, it should be around 2.5 Volts, this then sets the voltage on pins 9 to 16 which should also be about 2.5 Volts. Check that you haven't got a blob of solder or stray component lead causing a short between pins 1 and 2 of the PT2399.

Seconded. You could also look at R17/R22 which are the voltage divider which sets the bias level of the LFO. A wrong value or a short there would cause pin 2 to be out of whack.

Tom

[duck_arse]

you seem to be losing some volts between your input volts, 8V23, and the opamp and regulator, 7V82. as there is nothing shown on the circuit, this is not right, unless you're using a battery which is dying as you measure. 3rd for a solder blob.

[anotherjim]

PT2399 out. Is its pin 2 still the same volts as pin1? Power off. Use your meter to measure resistance pin 2 to pin 1 - it looks like there's a short there. With pcbs with top pads, it's possible, especially with sockets, to have run too much solder in from the back and it's pooled up on the top side amongst the socket pins.
If the faults not at the socket, check the track running from pin2 to the 33k R16 alongside the regulator.

[Fazzer]

I've had a poke around and the resistance between pin 1 and 2 with the chip out is 1 so no problem there.

chasing the voltages around it looks like I've got 2.5 ish everywhere after R22. The first time it hits 4.5 ish is on the positive side of C14 10uF cap feeding into the depth pot.

ps I'm using a battery to check but I think for this pedal I'm going to swap to more static power supply.

[anotherjim]

2.5v around IC1b is about right. As it's the modulator, voltage will be changing all the time around it.

Anything very far from 2.5v on IC1 pin 2 is fatally wrong.

Take out (or just lift one end) of R16,R18 & R19. With the PT2399 in and power on, there should be nothing to stop 2.5v appearing on it's pin 2 other than a dead PT2399 chip. You can confirm the PT2399 out of the board if you have a prototyping block or spare 16pin socket and wire +5v to pin 1 and -ve to pins 3&4 - then confirm 2.5v on pin 2.