comradehoser
Well-known member
Redid JFETs according to Chuck's mods here, ended up with 2n5457 at 1.1 and 1.3 IDSS in Q2 and Q4, 1.7 in Q5; J201s at 0.46 each in Q1 and Q3. This gave me the best sound and also the best stability to address the ducking and swelling I was experiencing with the "Dynamic" pot set below 10:00. (subsequently I measured the pot bring the voltage as low as 3v CCW--maybe outside of the intended range of the pedal).
Also jumpered R18 to the nearest VREF incoming voltage to R6.
So far, so good.
Lifted a leg off R20, subbed in the 50K trimpot for R19.
Had a good signal, dialed back the dynamic pot, and the pedal started gating and shut down.
Measured: Q2, Q4, and Q5 are all receiving 16v from VCC with Dynamic CW (or whatever variable VCC you dial in with the Dynamic pot), as well as the top side of R100. VREF seemed to be the issue, which according to Chuck's schematic should be somewhere around 8V or half the VCC. I was getting readings of 0.5v.
Since R18 to VRef seemed the most directly related to VRef, I reversed the R18 to VRef mod to ground again, and I had my pedal back, good signal range and control all the way back to CCW of Dynamic.
Until I didn't. Pedal shut down again, only lets through strangled and distorted signal peaks, VRef still around .5v--didn't measure when it was functional.
Continuity in the VREF section checks out--R100 to R101 to C104, as well as R101 and C104 (neg) to ground.
Could this just be component failure--say of C104, which is right at the root of VRef? I've never had a circuit work and then not work like this before.
Also jumpered R18 to the nearest VREF incoming voltage to R6.
So far, so good.
Lifted a leg off R20, subbed in the 50K trimpot for R19.
Had a good signal, dialed back the dynamic pot, and the pedal started gating and shut down.
Measured: Q2, Q4, and Q5 are all receiving 16v from VCC with Dynamic CW (or whatever variable VCC you dial in with the Dynamic pot), as well as the top side of R100. VREF seemed to be the issue, which according to Chuck's schematic should be somewhere around 8V or half the VCC. I was getting readings of 0.5v.
Since R18 to VRef seemed the most directly related to VRef, I reversed the R18 to VRef mod to ground again, and I had my pedal back, good signal range and control all the way back to CCW of Dynamic.
Until I didn't. Pedal shut down again, only lets through strangled and distorted signal peaks, VRef still around .5v--didn't measure when it was functional.
Continuity in the VREF section checks out--R100 to R101 to C104, as well as R101 and C104 (neg) to ground.
Could this just be component failure--say of C104, which is right at the root of VRef? I've never had a circuit work and then not work like this before.
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