Hi,
I'm new to effects and electronics in general (first post here!). I've successfully built a couple of fuzz circuits and decided to jump into a phase 45 circuit. Perhaps unshockingly, I'm now a little stuck...
I've been through the debugging thread here and at geofx and am still stuck. Here's what's happening, and what I do know so far:
1) this is the tonepad phase 45 circuit and layout.
2) Engaging the effect results in a very slight volume drop and what sounds like perhaps a small phase change, but no oscillation of the phase effect. The tone is slighlyt brighter than when bypassed.
3) I etched the circuit board myself--first time. Before populating the board I checked continuity on all the traces that were supposed to be connected. After populating I inspected we a magnifying glass and even checked for continuity in the couple of areas that I thought might be inadvertently shorted out. Everything seems to check out ok.
4) I substituted a matched pair of 2n5457 jfets for the specified 2n5952. I checked the pinout per the data sheet (and even tried flipping them based on the reports that some mentioned of incorrect pinout spec on the layout). I substituted .047 uf caps for the specified .05 uf. All other components are as specified.
5) Two jumpers are called for, and they are in place! (Almost missed that!)
6) power is supplied from a dc wall wart. 9.39 supplied volts.
Pin voltages are as follows:
Z1:
A: 0
K: 3.54
Q1:
G 3.54
S 3.54
D 1.50 (Adjustable from 0.81 - 3.34 depending on trimmer setting)
Q2: same as q1
IC1:
P1 3.54
P2 3.53
P3 3.54
P4 0.1 mv
P5 3.37
P6 3.54
P7 3.54
P8 9.38
IC2
P1 4.70
P2 4.69
P3 4.50
P4 0.2mv
P5 3.54
P6 3.53
P7 3.54
P8 9.38
I noted while searching the archives that pins 1-3 on ic2 are typically fluctuating in voltage--mine are rock stead at the listed values. I'm guessing that that's the root of no phase sweep...
Any suggestions would be greatly appreciated!
--Nathan