Hi, i build a dr boogey pedal on perfboard using the layout created by Chris Brown which is based on Gaussmarkov's revised schem. wired everything up already but only got sound when bypassed! when switched on, the LED does lights up but got no sound AT ALL out of it. checked back the continuity of all that supposed to be and all seems to be good/correct.
tried the audio probe, but the sound stopped after the 'Gate' foot of Q1 (the first j201). There's still sound at the 'Gate' foot but nothing after that ('Source', 'Drain' and following components). first i suspected the C17 cap is not good coz i had quite a hard time soldering especially for that cap (got some problem with my iron). but according to gaussmakorv schem, http://gaussmarkov.net/layouts/drboo/drboo-schem.png (http://gaussmarkov.net/layouts/drboo/drboo-schem.png), wouldn't the circuit still be working even without C17?
Or is it may be coz my j201 has failed? I already tried checking the voltage of the feet of the Q1 and all shows readings.
btw, here's the perf layout i followed.
(http://2.bp.blogspot.com/_2mvQNIEjC7g/Sk-gDo0ixwI/AAAAAAAAAFA/WAFpG9qT5QE/s400/boogie+layout+2.gif)
thanks in advance!
post the voltages on the Q's. You should have sound on the drains.
Have you biased the the Q's?
Double check the pinouts.
Not sure if I saw trimpots there.
Sometimes a trimpot and a fixed stop resistor helped me to find a range that the sensativity of the pot would allow nice 'fine tuning' to discover the needed value for the drain resistor for stable bias, for say, each J201 transistor, swapping the transistor sometimes made it easier to get a biased stage.
50k pot and a 47k resistor, with and without the resistor divides a 100k range in two parts, allowing the pot to have a smaller, hence less 'coarse' adjustment sensativity.
I decided that anything over about 100k to just get another transistor which doesn't require such a large value resistance to achieve drain bias.
You can open between the drain and drain resistor [or between the resistor and V+] to insert more resistance [try a pot with wiper and outside lugs wired in series.
To reduce resistance, jumper across the drain resistor.
Without the trimpots, I'd be wondering just how accurate those JFETs are biased.
Put your DMM probes on each of the outside legs of the JFETs and if they are around half of your supply voltage, it should give sound.
If not, you'll need to adjust the resistor near the JFET (which is why the trimpots are a good idea).
Or just use a trimpot to adjust it, then measure the trimpot when it's set accurately and then replace the pot with a resistor of that same value.
These are the Q readings
Q1
D : 8.6
S : 8.6
G : 8.18
Q2
D : 8.1
S : 0
G : 7.7
Q3
D : 4.74
S : 0.55
G : 0
Q4
D : 4.5
S : 0.56
G : 0
So... what should i check? pinout are where it supposed to be and connected to what is supposed to connect with.
anyhow, how to check whether a capacitor is still ok or not?
Those yellow 'VR1/2/3/4' are trimpots. i somehow couldn't bias the drain of Q1 and Q2 low enough nearing 4.5v
Where's a larger version of the layout that you used?
Can't seem to find it and can't read the one you posted.
Try and click the link below to see a bigger of the perf layout.
http://2.bp.blogspot.com/_2mvQNIEjC7g/Sk-gDo0ixwI/AAAAAAAAAFA/WAFpG9qT5QE/s1600-h/boogie+layout+2.gif (http://2.bp.blogspot.com/_2mvQNIEjC7g/Sk-gDo0ixwI/AAAAAAAAAFA/WAFpG9qT5QE/s1600-h/boogie+layout+2.gif)
Quote from: had_hc on July 15, 2009, 09:54:05 AM
i somehow couldn't bias the drain of Q1 and Q2 low enough nearing 4.5v
Well, there you have it. Start looking around those, especially look for shorts around Q1, try other trannies etc.
Might be dumb to say, but make sure you have C14 and C20 polarity correct.
The layout looks the same as the Gaussmarkov layout.
Since you're not able to get the bias down to the right range on Q1/Q2, check for solder bridges in that area.
If you have another JFET to test in those spots, that might be worth trying too.
EDIT: DOH! Sorry to previous poster, I was typing when you posted that!
i managed to get drain voltage of Q1 to around 4.5v but still couldn't figure out why can't i bias Q2 to 4.5v. the lowest was around 7.1v. all components seems to be in their respective places.
and still however, i got no sound at either source or drain of Q1, as before, last trace of sound is at Q1's gate. help me!! where should i look more?? there seem to be no short circuit or bridges wutsoever....
This may sound stupid, but what I did wrong with the Dr. was the offboard wiring. I put my guitarsignal to the output of the perf and vise versa... A week of troubleshooting, 2 minutes to fix
Quote from: had_hc on July 15, 2009, 01:47:45 PM
i managed to get drain voltage of Q1 to around 4.5v but still couldn't figure out why can't i bias Q2 to 4.5v. the lowest was around 7.1v. all components seems to be in their respective places.
and still however, i got no sound at either source or drain of Q1, as before, last trace of sound is at Q1's gate. help me!! where should i look more?? there seem to be no short circuit or bridges wutsoever....
Well, it sure looks like you've got a short between Q1's source and drain. Does your meter measure continuity between source and drain? Do you use sockets, so that you easily can swap the transistor?
Thanx all! i don't know what i did wrong but i got sound when enganged! only tuning needed now!
somehow i feel that there's not enough gain in my Dr. Boogey and the distortion is kinda.... fizzy/fuzzy i might say. very little bass present and really loose sound at palm-muting.
any reason's why it might be?
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.
just forget about the 4.5v bias now..and start tuning it by ear..this is my technique
- Set the dr B gain really low, with the guitar connected.
- Set the volume of the guitar so you get the cleanest sound...
- Pay attention to the background hum/hiss and move r4´s trim
- set the trim where the noise is louder
- Pay attention to the background hum/hiss and move r3´s trim
- set the trim where the noise is louder
- repeat for Q1 & Q2..
- Now.. pluck the strings gently, trying to get a clean sound (there will allways be distortion), and re-fine tune the trims to taste based on sound, touch response and clipping..by fine tune i mean microscopic turns!
- try different j201´s on Q1, Q2...you´d be surprised how much the selection of fets improves the sound.
With the gates that are above source, I'm thinking there's a problem with the bias unrelated to, and not affected much by the trimpot settings.
Where's the schemati
http://gaussmarkov.net/layouts/drboo/drboo-schem.png
Quote from: petemoore on July 17, 2009, 09:42:09 AM
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
Quote from: had_hc on July 17, 2009, 09:00:00 PM
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.
Quote from: had_hc on July 17, 2009, 09:00:00 PM
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.
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...
Oh, now somehow, all D, S , G of Q2 has the same voltages! wtf??? what might cause this? bridges as usual?
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!
...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!!
;D ;D ;D
thanx all!
this is a very exciting experience!
ok. i'm really diggin' the distortion tone out of this monster ;D ;D 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 ;D ;D
one last thing, this pedal is very QUIET!! without playing any notes, this pedal that i built is suprisingly queit. too quiet perhaps. hmmmmm... :-\ :-\
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.
You're sure it's not the setup on your guitar that causes the strings to stop vibrating? Too low action could cause this.
Quote from: frokost on July 31, 2009, 09:13:00 AM
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..