PorkBarrel no Chorus

Started by climberboy, March 08, 2014, 09:54:00 AM

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climberboy

Hey everybody,
I'm on the last of a bunch of pedals that I wanted to build and this one has me stuck.

1.What does it do, not do, and sound like?= The bypass works just fine, but when I turn the effect on it sounds like nothing has changed. The guitar still comes through the amp, but there is no chorus effect whatsoever. The depth, rate, and trim pots don't seem to do anything. I've seen this problem on here before, but couldn't find a solution.
2.Name of the circuit = PorkBarrel Chorus from Madbean
3.Source of the circuit (URL of schematic or project) = http://www.madbeanpedals.com/projects/PorkBarrel/docs/PorkBarrel.pdf
4.Any modifications to the circuit? Y or N= No, but I am using the MN3007 version where I omit D4 (Zener diode) and use a MN3101
5.Any parts substitutions? If yes, list them= No
6.Positive ground to negative ground conversion? Y or N= I'm not exactly sure what this means. I'm using the madbean offboard wiring on page two: http://www.madbeanpedals.com/tutorials/downloads/StandardWiring_MBP.pdf
7. What is the out of circuit battery voltage? = 8.69 V
Voltage at the circuit board end of the red battery lead = 8.59 V
Voltage at the circuit board end of the black battery lead = 0 V

Q1
C =8.40
B =2.74
E =3.33

Q2
C=8.40
B=3.64
E=3.52

Q3
C=8.40
B=2.97
E=3.38

Q4
C=6.90
B=0.44
E=0

Q5
C=8.30
B=3.47
E=3.47

IC1
P1=4.26
P2=4.26
P3=4.20
P4=0
P5=4.23
P6=4.25
P7=4.25
P8=8.50

IC2
P1=Reading bouncing between 2V to 5.5V
P2=4.22
P3=bouncing between 3.5V to 4.8V
P4=0
P5=4.20
P6=3.91
P7=Bouncing between 3.5 to 4.8V
P8=8.45

IC3
P1=8.37
P2=4.28
P3=0
P4=4.32
P5=0.35
P6=7.30
P7=2.73
P8=0.57

IC4
P1=7.90
P2=4.32
P3=3.51
P4=0.57
P5=7.22
P6=4.27
P7=7.51
P8=7.51

D1
A (anode, the non-band end) =2.7
K (cathode, the banded end) =6.97

D2
A =1.61
K =2.78

D3
A =0
K =8.42

Ending battery voltage= 8.43

When I put my finger across the terminals on the rate pot, I can hear a clicking that changes speed as I turn the rate pot. I used a sharp knife to go in between all of the solder points, so I'm pretty positive that there are no solder bridges. Also, a lot of the voltages were bouncing up and down (but staying within a volt or so), so I just took an approximate average. The IC's that I noted were fluctuating a LOT, so that's why I mentioned it up there. Thanks!

PRR

> Q5
> B=3.47
> E=3.47


This stands-out. Suspect a solder-blob here.

B-E short here would kill the delayed signal.

(Another proof would be a signal tracer. Signal at IC4 pin 7/8 but no signal at Q5 E would hint at a Q5 problem.)

Many of your other transistor numbers look "wrong" but would be right if you got B and E reversed in note-taking.

> Q1
> C =8.40
> B =2.74
> E =3.33


B should be 0.6V higher than E; you show it lower. However wrong-wiring won't give these numbers, so I suspect the transistor is happy and the notes have been transposed.
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climberboy

The Q5 solder points all look good. However, E and B are giving the readings that bounce around a bit, so it's hard to say if one is 0.6V higher than the other. I've never had this bouncing voltage problem before with other pedals. Is this normal? I'm just hoping there's nothing wrong with the two expensive opamps in this one...

climberboy

Any other ideas? I scraped in between all the solder points again and I'm positive there's not any bridges. I checked all the resistors and all the colors bands are correct, but some of the measurements don't match the color bands. I'm not sure what's up with that. For instance, R31 is 10k, but it measures 6.2k ohm