Dr. Boogey Problem

[jimosity]

I built the Dr. Boogey project from Gaussmarkov.
I can't seem to get it to work; I have looked over the schematic and traced all of the board a couple times and just don't see any problems.
The only thing that I didn't do is use the 100k trim pots, instead I tried 100k fixed resistors, then I figured that might be a problem so I replaced them with 51k resistors...  I get no sound at all.
The led lights up and when I turn the effect off my guitar signal goes thru clean; but when engaged, I get nothing at all.

Any ideas?

I thought it might be a problem with the J201's and their leg placement, but I laid them out exactly as the board diagram shows, which appears to be in line with the way the data sheet from Fairchild shows the J201 legging.
I'm kind of lost as to what to check next.

[Auke Haarsma]

The trimpots are there to bias the Drains of the J201 iirc. What voltage do you measure on the drains?

For starters it would be good if you aim for 1/2Vcc (often 4.5V) on the drains.

[dschwartz]

The only thing that I didn't do is use the 100k trim pots, instead I tried 100k fixed resistors, then I figured that might be a problem so I replaced them with 51k resistors...  I get no sound at all.
The led lights up and when I turn the effect off my guitar signal goes thru clean; but when engaged, I get nothing at all.

if u want to use fixed resistors, you should use trimpots first, bias the fets coprrectly, and measure each trim..then replace for fixed resistors of the values you found on the trimpots..
the sweetspot for each fet is pretty small, so just guessing resistor values for the drains is a pretty bad idea..

[jimosity]

OK - So I replaced the fixed resistors with trim pots, then set the bias on each to around 4.5, but had some weird biasing issues with Q3, it's like it would jump from 7.0-5.5 down to 0.4 and nothing in between.
I thought maybe it was in backwards; nope...
Then I thought maybe I had a bad J201, so I replaced it - same issue.

I then figure I'd plug it in and see what it sounded like (if anything).
It was very sizzley and it sounded like there was a really heavy noise gate on it that would clip the signal anytime you weren't hitting the strings.
I then said hell with it and started tweaking the trim pots and got to a pretty damn good tone overall, but then when I checked the bias on the J201's again, they were all over the place.

Can somebody give me a "biasing J201's for dummies" course?  (as in - connect this to that, just to make sure I'm doing it right....)
I've searched a few threads about biasing and even read the FAQ blurb about biasing JFETs, but I guess I'm dumb or something.
<This is the first time I've ever had to bias jfets, so be gentle...it's also only my second or third pedal that actually does something...)

While I did manage to get a pretty damn good tone that really did sound like any of the real Dual Recto's I've ever owned, there were still a few issues.
The Gain pot seemed to only work when cranked 100% and then nothing when backed down at all. (I was using a 1M pot).
I tried a 500k pot, that didn't seem to help a whole lot, but was a very slight improvement.
Also, all of the other controls work great except for the treble control.  I get no change in tone at all out of that pot.
I didn't try replacing that pot.

[dschwartz]

OK - So I replaced the fixed resistors with trim pots, then set the bias on each to around 4.5, but had some weird biasing issues with Q3, it's like it would jump from 7.0-5.5 down to 0.4 and nothing in between.
I thought maybe it was in backwards; nope...
Then I thought maybe I had a bad J201, so I replaced it - same issue.

I then figure I'd plug it in and see what it sounded like (if anything).
It was very sizzley and it sounded like there was a really heavy noise gate on it that would clip the signal anytime you weren't hitting the strings.
I then said hell with it and started tweaking the trim pots and got to a pretty damn good tone overall, but then when I checked the bias on the J201's again, they were all over the place.

Can somebody give me a "biasing J201's for dummies" course?  (as in - connect this to that, just to make sure I'm doing it right....)
I've searched a few threads about biasing and even read the FAQ blurb about biasing JFETs, but I guess I'm dumb or something.
<This is the first time I've ever had to bias jfets, so be gentle...it's also only my second or third pedal that actually does something...)

While I did manage to get a pretty damn good tone that really did sound like any of the real Dual Recto's I've ever owned, there were still a few issues.
The Gain pot seemed to only work when cranked 100% and then nothing when backed down at all. (I was using a 1M pot).
I tried a 500k pot, that didn't seem to help a whole lot, but was a very slight improvement.
Also, all of the other controls work great except for the treble control.  I get no change in tone at all out of that pot.
I didn't try replacing that pot.

your'e doing fine..be patient...
the best way to bias fets is the way you already did..by ear..let them sit where they sound best..
gain pot....well with gain at zero you get no sound, that´s the way it works..

treble control..recheck wiring and solders..probably something wrong there..measure the pot ,too..

congratz.at least u made it work!!!  it is not a very newbie-friendly project!

[rock_god_dan]

Start with biasing the drain of the fets at 4.5v, had the same problem too. If the output sounds like it's heavily noise-gated, one of the fets is probably being fed lower than optimal voltage.

[rogeryu_ph]

Timing guys,  I breadboard the Boogey just last night. Me also have difficult biasing the trim pots. Is there a reference voltage chart available in website?  Isn't it you can not bias the Q5 to half volt?  Can I also replace the source resistor to ground a higher value?

Roger 

[Auke Haarsma]

As said, just bias to 4.5V (if you have a 9V supply). Then bias by ear. If you don't get sound with bias at 4.5V you may have made an error on the breadboad.

To simplify the circuit you could drop the tone-section and replace it whit a SWTC (check muzique.com)

[dschwartz]

Timing guys,  I breadboard the Boogey just last night. Me also have difficult biasing the trim pots. Is there a reference voltage chart available in website?  Isn't it you can not bias the Q5 to half volt?  Can I also replace the source resistor to ground a higher value?

Roger 

Q5 is a buffer, so it doesn´t need to be biased (the same way the others do)

common errors i found on people triyng to bias the fets:
- inverted fets
- wrong type of fets
- trying to bias with no fets..just empty sockets
- measuring from b+ or gate to ground..and not from drain
- using a battery and not a stable power supply
- NOT USING YOUR EARS!
- bridged traces
- wrong value trimpots
- not enough patience and parkinson hands to find the sweetspot
- cheap bad trimpots

i´m sure you're doing one of those......
a hint: start from Q4 to Q1, trimming by ear..let it stay where most noise and/or hum
good luck!