Dr. Boogey help!

[had_hc]

  I kind of remember DB as being a number of seriesed Jfet Stages, no schematic limits the dialogue and accuracy for me.
D : 8.6
S : 8.6
G : 8.18
  Source should be kinda near Gnd., Source above gate, check them' resistances to ground around the S/G, also check the R value between D and V+, all these pins are around V+, and should be D in the middle of the supply, S and G nearish ground voltage.
Q2
D : 8.1
S : 0
G : 7.7
  I would start checking the ground connections, is the source grounded?
Q3
D : 4.74
S : 0.55
G : 0
   This is the kind of voltage I'm talking about ... see if you can make the other stages resemble this one more, use the DMM to compare anything / everything possible with the DMM to see how the offbias stages compare, especially resistance wise.
Q4
D : 4.5
S : 0.56
G : 0
  Here...source above gate, 4.5v would be spot on with a 9v battery, but I'd still check sound and bias by ear, this stage should be working fine.

fixed my Q1 already. the voltages are like Q3 and Q4. However, Q2 is still like that. what do u mean with source grounded for Q2? from the schematics (gaussmakorv's one), it doesn't directly connected to ground. There's R6 and C6 between it to the ground according to 'em.

dschwartz.
I'll try to do ur biasing techniques.

me thinks, Q2 is what makes my DB sounds kinda crappy (to my ears) coz the gate is above source there in terms of voltages. any tips what to look for there? any common error?


p/s btw, this is actually my first pedal built. i figured that coz i hav mod some pedals and even my tbe amp, i can directly do this one! haha

[frokost]

fixed my Q1 already. the voltages are like Q3 and Q4. However, Q2 is still like that. what do u mean with source grounded for Q2? from the schematics (gaussmakorv's one), it doesn't directly connected to ground. There's R6 and C6 between it to the ground according to 'em.

Exactly. So it shouldn't read 0 volts.

dschwartz.
I'll try to do ur biasing techniques.

me thinks, Q2 is what makes my DB sounds kinda crappy (to my ears) coz the gate is above source there in terms of voltages. any tips what to look for there? any common error?

You're right, Q2 is a problem. As for common errors, there are the usual ones.. Check your wiring (the gain pot is close by), check for solder bridges, shorts of any variety, transistor pinout (again ) and cold solder joints. You know where the problem is, it's just a matter of locating exactly where.

[had_hc]

aaargghh! i resoldered around Q2 and finally got the 'desired' voltages for D, S, G. but when i plugged in, got no sound!

HOWEVER, with the volume at full and playing with the trimmer, i could hear some sound but very low volume sound.

so.... checking wuteva reasons it might be...

[had_hc]

Oh, now somehow, all D, S , G of Q2 has the same voltages! wtf??? what might cause this? bridges as usual?

[budjb]

I just built one of these and got lucky - it just worked.  I was very, very careful when soldering the board  though.  See if there's the possibility of any of the pins on the transistor shorting each other.  I scraped in between any solder points if there was even the slightest doubt that it was clean.  A small flat screwdriver or the pin from a socket worked well for me.

Also make sure your transistors are seated correctly.  I got it all working without trimming the leads on the J201's, and then took them all out and cut them to length.  Once everything was back in, I could hear sound but it was very, very quiet.  Turns out a pin on Q5 didn't make it into the socket, and once I reseated it all was well.

Good luck, the effort will be worth it!

[had_hc]

...and the monster is alive!!!! what a high gain this pedal has! it was bad jfets after all. bought a couple new ones with sockets and soldered 'em up. and WALLA!!


thanx all!
this is a very exciting experience!

[had_hc]

ok. i'm really diggin' the distortion tone out of this monster  but somehow not quite satisfied with the sustain of the notes. some notes especially high ones don't have long sustain as others (and as i like).

and also the decaying of the notes. it somehow juz stop itself at the end of it. like too sudden for me (although with long sustain with some of the notes). don't know if guys understand what i'm saying here. hehe 

one last thing, this pedal is very QUIET!! without playing any notes, this pedal that i built is suprisingly queit. too quiet perhaps. hmmmmm... 

[budjb]

It sounds like the jfets are mis-biased.  I'd make another pass at checking the voltages on the drain of each one that has a trimmer attached to it.  They should be anywhere from 4.5V to 5.5V.

[frokost]

You're sure it's not the setup on your guitar that causes the strings to stop vibrating? Too low action could cause this.

[had_hc]

You're sure it's not the setup on your guitar that causes the strings to stop vibrating? Too low action could cause this.

hmm... that's probably one of the case coz i haven't set up my guitar for a long time. but still, the sudden stop at the end of the sustain is somehow not to my liking.

and i'm not listening much difference in presence control. but probably juz my ears. what does a presence control suppose to control anyways?

by the way, i decide to juz use the current bias for atleast a week to really listen to the pedal first before making any more changes. probably gotta mod my amp (EVJ) too..