A somewhat different fuzz

[mth5044]

I based the schematic off the OP schematic. I see you posted some amendments later. I'll fix that up,
Thanks.

[mth5044]

.

[tubegeek]

Missing 10K is between Q2 base and C4 (in path to clipping diodes.)

[mth5044]

Yikes, I'll get it right someday. Have you had a go at it yet?

[tubegeek]

I wish!
Tomorrow?

[Davelectro]

Actually, that resistor is not in the first scheme posted by Gus.

I've built this fuzz on preperf and put a socket for that resistor. I didn't try it yet.

[Gus]

Reply #29 is what I built

[tubegeek]

Quick trial.

NO guitar sound. Some shhh which varies in level with the volume control.

Voltages:

9V node: 9.2V

Q1: C: 7.0, B: .57 V, E: 2 mV

Q2: C: 6.65, B: .57, E: 2 mV.

Any guesses?

Thanks!

[deafbutpicky]

check the emitter resistors, you might have some cold solder joints

[Gus]

The voltages look right for lower beta transistors and emitter resistors.  I selected higher beta transistors for lower collector voltages and higher collector currents I also grounded the emitters.

I would seem something else is not passing signal.  Did you check the PCB with a meter for unwanted connection between copper areas before building?

Remove the battery
Check the gain control with a meter set to ohms.  Then check the circuit with a meter set to ohms and work from in to out checking for wanted and unwanted connections also check caps for shorts and resistors for correct values.  Are the jacks, wires good etc.

What transistors did you use?

2mv shows the emitters are not grounded
Looks like you used 10 ohms
9.2 -7 = 2.2 first stage 2.2VDC/10k = .22ma
.22ma x 10ohm = .0022volts

[tubegeek]

OK next steps are clear, THANK YOU!!

I appreciate the help!

[tubegeek]

you might have some cold solder joints

dingdingding we have a winner! Cold solder joints it was, sir. Not the only cold problem we've been having here in Brooklyn 

So: the PCB is VERIFIED. While I was all busy with life & stuff, a Tayda order came in with some 2N5089's (all 20 test in a tight cluster around 500 hFE on my multimeter) and some Schottky diodes and some other stuff.

I put two 2n5089's that tested about 520-ish into the sockets and got out my magnifying glass. Indeed there were some bad solder joints here and there.
After I fixed those the only problem I had was, my amp sounded like it might blow up. 

Even without it in any kind of box at all, I'd say the noise factor was pretty minimal. I was able to get some screamy feedback, some ballsy crunch, some blue distorted lead tones, all sorts of stuff. Nice crazy-box indeed.

Thanks for hanging in there with me, guys.

Gus: want any boards? It's the least I can do. Thanks for sharing this interesting design with the community, it's a pretty sweet one.

[Davelectro]

Wow, I didn't even try this circuit yet and i'm already regretting my 100R emitter resistors.  

[tubegeek]

Wow, I didn't even try this circuit yet and i'm already regretting my 100R emitter resistors.  

I stuffed/soldered/tested a second board last night, with 7R5 at that position, sounds great. I had to make one other substitution: 3M3 instead of 2M2 on the input, that shouldn't really change anything.

I still haven't drilled any boxes yet, and the open boards are usably quiet anyhow - I only pick up a tiny bit of RF interference, probably WiFi. I took pinkjimi's suggestion and added a ground wire to the back of the gain pot (500K linear on both builds) and I also braided all 4 wires to that pot together.

Here's a couple pics:

[pinkjimiphoton]

looks great bro!!

[tubegeek]

I forgot to mention: the voltages shown on Gus's simulation are spot on - within a tiny fraction of a volt in every case.

[Gus]

Some things to try
grounded emitters
other clipping diodes a set of 1n400(1,2,3 etc.) might be fun
Adjust the 10K resistor value in series with the diodes try a 22K

What I posted at reply 29 is a good set of starting values.  

Have you tried it on bass?

[tubegeek]

No bass experiments yet for me - I don't own one. I was thinking about switchable symmetrical/asymmetrical diodes but I want to get an example boxed up before anything else gets added in.

[Gus]

Anyone else try this circuit?

I have a different circuit based off the ASDF simmed.

[tubegeek]

I'm almost ready to post gut shots, BTW. I've been experimenting with Envirotex and it takes a while for a couple of coats of that stuff to dry, plus I haven't exactly done it right so far....

What changes have you made, Gus?