Getting positive side only

[simonrichie]

Hey folks,

Just built the Death By Audio Supersonic Fuzz Gun.

I'm getting voltage readings on all V+ points, but no grounds.

Here's the schematic:

http://2.bp.blogspot.com/-znDD59ulovI/TxdhUN-MnnI/AAAAAAAAAng/uoII_zb2Tik/s1600/supersonicfuzzgun.png

I get voltage to everything above the through line (everything that goes directly to V+), including Density pot, R1, R2, R3, R6, R7, R9, C3, C4, C5, base and emitter of Q1 and Q2, base and collector of Q3, and the bias pot.

I'm assuming it's a ground issue, but I have no idea where to start.

Thoughts?

-DP

[simonrichie]

Also, I notice that I do get some of those other readings when I unplug from the output.

-DP

[simonrichie]

I figured out that I'm getting signal to C1 and C2, but only the right side (schematic-wise) and not input side. WTF?

[mth5044]

What do you mean you're not getting voltage readings on grounds? You aren't supposed to, relative to the 9V, they should read 0. See the debugging thread sticky and answer those questions for better help! Your layout and pictures of your board might help.

[antonis]

Am I the only one that sees into an obvious schematic mistake..

[Brisance]

Am I the only one that sees into an obvious schematic mistake..

input cap floating?

[induction]

Am I the only one that sees into an obvious schematic mistake..

input cap floating?

I would have guessed the reversed 2N5089's. In any case, it's a DBA circuit, so I'm not sure that the concept of 'mistake' really applies here.

[antonis]

I would have guessed the reversed 2N5089's. In any case, it's a DBA circuit, so I'm not sure that the concept of 'mistake' really applies here.

I'm not familiarized with reverse-active mode operation but I think that the reverse bias voltage is close enough to breakdown..

[anotherjim]

I'm not familiar with that reversed Tr topology either. Given the location of the Fuzz control, it looks like the distortion is meant to be from overdriving Q3. That requires normal gain operation from Q1 & 2 I'd have thought. So I come down on the side of drawing error -  Q1&2 shown with emitters and collectors reversed.

[duck_arse]

[antonis - search "DBA Fuzz War" (try 'the other place') to see the extent of the reversed transistors lurk.]

[induction]

I'm not familiar with that reversed Tr topology either. Given the location of the Fuzz control, it looks like the distortion is meant to be from overdriving Q3. That requires normal gain operation from Q1 & 2 I'd have thought. So I come down on the side of drawing error -  Q1&2 shown with emitters and collectors reversed.

The phrase 'normal gain operation' has no place in a discussion about a DBA circuit. 

[anotherjim]

Ah, Tr's deliberately reverse for low gain.
So the base and emitters of Q1&2 ought to have some positive voltage somewhere near halfway between 0 and 9v . If not, you likely have NO ground connection.
If you have standard power switching using negative power supply wire to a TRS input jack, there will still be positive voltage readings on some of the circuit because the positive power wire is ALWAYS connected to the battery or power jack. Correct wiring would be circuit ground to Sleeve contact of the jack and power negative to the Ring contact. With a plug in, the power negative connects via the jack sleeve to the negative supply.

[simonrichie]

What do you mean you're not getting voltage readings on grounds? You aren't supposed to, relative to the 9V, they should read 0. See the debugging thread sticky and answer those questions for better help! Your layout and pictures of your board might help.

My apologies for not reading the debugging thread before posting.

Check pinouts of transistors? - Yes

1.What does it do, not do, and sound like? - bypass works. Engaged, nothing, unless I switch to "Gate" (or oscillation?) and then a harsh crazy noise barely effected by the knobs.

2.Name of the circuit - Death By Audio Supersonic Fuzz Gun

3.Source of the circuit (URL of schematic or project) - schematic linked previously; built off of this vero layout: http://tagboardeffects.blogspot.com/2012/04/death-by-audio-supersonic-fuzz-gun.html

4.Any modifications to the circuit? Y or N - No.

5.Any parts substitutions? - I used 2n5088s in place of the 2n5089s. Many people reported better results with this.

6.Positive ground to negative ground conversion? - Not that I'm aware of.

7.What is the out of circuit battery voltage? - 8.85v.

8.Voltage at the circuit board end of the red battery lead - (Where "9V" is on veroboard?) 8.75v

9.Voltage at the circuit board end of the black battery lead - (Where "Ground" is on veroboard?) 0

Q1
C = 0
B = .54
E = 1.0

Q2
C= 0
B= .54
E= .89

Q3
C= 1.94 (begins at 8v or more then drops slowly down to 1.94. If I held the lead longer, it might keep dropping.)
B= .82 (begins at around 1v then drops slowly to .82)
E= .04

D1 - Red 5mm LED (not on schematic, but added with 2k2 resistor on the vero layout) - 2.43

C1 - .54
C2 - .54
C3 - 1.01
C4 - .54
C5 - 1v+ then slowly drops. Tried again, began at .6 then began going up.
C6 - 3v+ then slowly drops
C7 - 0

Correct wiring would be circuit ground to Sleeve contact of the jack and power negative to the Ring contact. With a plug in, the power negative connects via the jack sleeve to the negative supply.

Circuit ground goes to sleeve, power goes to ring.

However, I've been screwed up with ground issues before, so here's what I've got going on:

circuit ground to output jack sleeve
circuit ground to Fuzz 3
circuit ground to input jack sleeve
power ground to battery snap and output jack ring
Fuzz 3 to Level 1 AND to 3PDT 2

[anotherjim]

Ok, have you fitted the un-named switch (I'll think of it as a "range" switch) that puts 10k in the ground of Q1&2? I think Q2 emitter should be higher volts, and the 10k should raise it. If not fitted, can you fit a 10k resistor in it's place to see what happens?

The slow changing voltages on Q3 I would say are due to C5 having to charge though the 4.7M R7, which would take more than 10 seconds to stabilize. Check the polarity of those electrolytic caps though, because if reverse, they can prevent bias on the transistors from ever stabilizing.

Scary circuit, all the way through  - good luck

[simonrichie]

Yes, there's the 10K resistor connecting Sw3 to Sw1 and the collectors of Qs 1 and 2.

I clipped the V+, ground, in, and out wires and hooked them up to my breakout box. Now it works. So the issue lies somewhere in my input and output jacks, DC jack, or 3PDT, or the wiring of those things.

Lesson learned: Build it, test it, box it, rock it.

[anotherjim]

Good. What does it sound like?
Usually it's
Build
Test
Fix
Test
Box
Test
Fix.
Rock

Don't be afraid to use the meter on continuity test to test your wiring in the box - before you even power it up.
Have a couple of jack plugs with the shells removed so you can test the sockets work through the contacts. Also get a 2.1mm DC plug so you can check that.
Check for continuity from each connect on the board to everything it should connect to.
Then test adjacent metal work/other contact to make sure it doesn't connect to things it shouldn't connect to.
Doesn't take long and the intermittent beeping makes you a Stockhausen.

[duck_arse]

with me it's usuallly pencil
paper
scissors
rock
resolder.

and the stockhausens on my meter got too much for me yesterday, I took the cutters to the beeper wires.

I've been wrestling a build this week, I tested continuity from here to here, so I knew wires were all good, tested supply to ground etc, jambed it all in, and the led indicator stopped me in my tracks. much swearing and de-boxing and wire kid-gloving later, turns out to be the millenium mosfet is dud. hacked that back together, into the box again, and now it crackles.

gah!

[simonrichie]

Sounds like this: https://www.youtube.com/watch?v=Y6kfViHeevM

HIGHLY gated. Oscillation mode is just noise, and if I ever build this again, I'll make that a stompswitch. It might be cool to kick that on as a lead in to a song. I tried using my foot on the toggle, but that's not so good.

In the end, bonehead that I am, I found that the problem is that I somehow managed to switch the input and output jacks. I had an "A-HA!" moment, swapped the cables, and it worked. I have no explanation for my stupidity.

[pinkjimiphoton]

What do you mean you're not getting voltage readings on grounds? You aren't supposed to, relative to the 9V, they should read 0. See the debugging thread sticky and answer those questions for better help! Your layout and pictures of your board might help.

ummm, +1

[pinkjimiphoton]

fwiw, reverse beta'd q's can sound REAL good. it's distortion, we're not looking for linearity, we're looking to exploit stuff to intentionally destroy the input signal.
depending on the circuit, you can get anything from a horrible gated fuzz to a very smooth and tubey one. there's all kinds of biasing ranges i've found work with some reversed transistors... you can find small windows where you can get some totally unexpected and vERY useable distortion tones.
jmo

ymmv