Duende Problems!!!

[Barcode80]

Okay, I just perfed up the Duende booster perf layout in Dragonfly's gallery. First, there is a mistake in the perf layout, as the trace from the trimpot to the drain of Q1 is missing. i had to check the pcb layout to see it.

so i trimmed the voltage on the drain to 4.5 volts. when i engage the effect, i get barely any signal. i mean BARELY any signal. i checked for solder bridges, and i'm certain there are none.

S and G both show 0 volts, so maybe there is a prob with the jfet? the D is biased to 4.49 volts

[petemoore]

S and G both show 0 volts, so maybe there is a prob with the jfet? the D is biased to 4.49 volts
  Maybe...did you use a socket?...have another?
  I would suspect the resistor network throwing the bias off, and would check for ground continuity at the S/G pins [because they're measuring 0v which is the ground reference voltage], if continuity exists, it is probably a solder bridge or other trace somewhere, making a misconnection to ground.
  The source needs to be above the gate for a Jfet to bias.

[Barcode80]

but according to the layout, source IS tied to ground.

http://aronnelson.com/gallery/album32/DUENDE_JFET_BOOSTER_PCB

here is the layout i'm using. the source of the fet goes straight to ground.

[petemoore]

http://www.geocities.com/tpe123/folkurban/fuzz/snippets.html
  Yes...it is !
  ok..do you have the 1meg pot [on the gate] turned toward the middle, if it's all the way one way of course the gate'd be grounded.

[Barcode80]

turned all the way down, i get nothing, turned all the way up, i get the muffled faint signal. i used a 500k, so i am betting that might be the problem...

[burnt fingers]

Double check the pinout of your jfet. It may not neccesarily be the same as the layout shows. 

Scott

[Barcode80]

i'll socket it tomorrow, as i hard wired this one. though i did heat sink it so i don't think i fried it. i will try that tomorrow and post results. so far i'm on 5 unsuccessful builds in 2 days, i'm bout to pack it in and give up boxes all together.

[burnt fingers]

Don't pack it up. Just walk away for awhile.  5 builds in two days seems like rushing it.

I usually take a few hours to populate a board,do offboard wiring  and another hour or so to stuff the box. 
Taking it slow will increase your chances of success. 

BTW.  When I was first getting into this, I tried to breadboard the Duende and was super pissed that it didn't work.  I told my wife that if I'm so lame I can't get a small booster to work, I have no business doing this.  I figured out some time later that the pinout on my jfet was different than I thought.

Scott

[Dragonfly]

just sit back, collect your thoughts, and go through it logically...its almost always something small and stupid.

i had reposted the corrected pcb...forgot to change the perf (drain trace error)...i'll get that changed...everything else should be good though

AC

[MartyMart]

Barcode, dont give up mate ... circuits are totally unforgiving of even the smallest
mistake !  .... "Mother nature" as RG put's it ... is always trying to tell you something...

After many hundreds of builds, i STILL do the following things - EVEN on a simple
circuit :

Look up the pinout data sheet for the devices that I'm using ( even if I know it - I check it ! )
Check the resistor value with a DMM ( 4k7 looks VERY much like a 470k ! )
Carefully check the capacitor markings for the correct value ( is it 102 or 103 ! )
Keep soldering station clean and the "tip" tinned and hot !
Check with a mag glass for "solder bridges" ( have found some that are as thin as a hair ! this will still conduct )

MOST IMPORTANT <<< TAKE YOUR TIME AND DONT GET ANGRY >>>
This path just leads to frustration and failure

Come back a day or two later, print off a schem and go through it with a "highlighter" pen
Check off  every " connection node " with the pen and your circuit.

I've even had a "DUH!!" moment or two, wondering why the circuit doesn't work and looking
at an empty 8 pin DIL socket  !! 

Marty.

[petemoore]

  Count the # of connections at each node, make sure board population follows schematic.
  Measure each resistor just prior to installing it.
  Jfets...GSD, DSG, SGD, ETC...lots of choices = lots of chances for mispinout.

[Barcode80]

yeah, i think my first step when i get home is going to be to socket that tranny and replace it minding the pinout. we shall see....