Zvex Fuzzolo

[Ciaran Haslett]

My first trace/schematic/breadboard verification



EDIT:  Layout now VERIFIED by Travis.  

[IvIark]

Nice job buddy, no doubt this will end up on the site at some point soon(ish)

[Travis]

Awesome, dude! Which components were the ones you weren't sure about? Just checking so I can socket those. I should have time to try it tomorrow

[Ciaran Haslett]

I originally drew R10 as 100r but I breadboarded it yesterday and found that 10k (suggested by nocentelli and present in the Woolly Mammoth) was correct.  Sounds identical to the original I traced.  I was also unsure of D2 but both 9.1v and 12v are found in the super hard on so I used a 9.1v zener.

I drew the layout with a switch for selecting between passive pickups and active.  Since I exclusively use passive pups I only tested thru the 750r input resistor so if I were you I'd socket the 39k and play with that if you have an active guitar.

Or leave the switch out and move the input wire to whichever input path you would use with your rig.

Looking forward to your build

Ciaran

[Ciaran Haslett]

Forgot to mention....a log pot for volume is a MUST.  I accidentally started with a lin and it almost took my head off!  

[Travis]

Got no sound from my board right now. Probably no more time to troubleshoot it right now either

[Ciaran Haslett]

Nightmare!!!

When on the bb i missed grounding the emitter of q1 and was left scratching my head for a bit.  The signal path is pretty straight forward in this so very easy to probe.  Also note the cuts under the 100k and 100n components.

I won't be at my desk till Monday so if I don't hear back from you by then I'll give it a go.

[Travis]

I'm away from home now, but I may have missed the cut under the 100n. I'm pretty sure I can get it working this weekend :P

[Travis]

Ok after correcting that dumb mistake it works!

[Ciaran Haslett]

Excellent job lad

I've updated the post to include your verification.  Cheers again.

[Travis]

I've got one caveat though now that I test it out more. When I turn the PW knob all the way up I'm getting oscillation

Maybe it's because it's unboxed, but I think it's too loud to be just that. Also I'm getting some nasty sounds on the (gated) note decay

Seems like a tranny problem. Maybe I'm not in the right hfe ballpark or maybe I need to bias it

[tnakatani]

Hi, new user here.

First off, thank you Ciaran for the schematic and layout!

I've built this as well and I'm getting similar symptoms to Travis with oscillation and note decay.

I was watching a video about the original and I saw that there is a resistor jumpered on the back of the PCB.  Not sure if its a 7.5K or 750ohm resistor:



If it's a 750ohm, I'm assuming that's the series resistor at the input?  Or is it a 7.5K that's missing somewhere?

I'll add some pics of my build for reference:

[Silver Blues]

Resistor bands are violet, green, red so the resistor is 7K5. No idea where that's supposed to go though.

[Ciaran Haslett]

Hi lads

Sorry I missed all this.  Been very busy lately with client projects its hard to get the time to sit down and enjoy some personal tinkering (jesus that sounds awful!!!)

That is indeed a 7k5 thats not on my schematic!  So sorry I missed this.  I can't tell where its supposed to go from the photos I took so I've just asked the owner to bring it in to me.  He won't get in till Tuesday so hold fire until then.  I'll get to the bottom of this then and report back.

Sorry again lads.

[Travis]

Thanks for bringing this up tnakatani

I had forgotten about this one. I'll be on standby waiting to test that fix. Thanks for the effort guys

[Ciaran Haslett]

Right lads.... I've finally got to the bottom of this.  So the good news and bad news.

Good news... The schematic and Layout are correct.  I've put mine on the breadboard again and tested it side by side with the original and its identical.  When pushed both oscillate just a touch (there's so much volume).  The decays on both are weird.  Some chirps and phantom notes.  You can actually find examples of these in some Youtube demos.

Now the bad news...

There must be two versions of this PCB cos my one doesn't have a 7k5 tacked to the back.  In fact, if you look closely at the pic you posted tnakatani, you can see what looks like a trace cut under the right leg of that 7k5.  Looks to me like there was as PCB design error that was temporarily fixed with the 7k5 then permanently removed with a PCB revision.

Based on the "newer" PCB I've been using it looks like the 7k5 would have been tacked on in series with the Active resistor and before the input cap so it doesn't look like that will help us.  You may also notice a extra resistor to the right of that 7k5 when looking at the "new" PCB.  Its the CLR on the new board.  I've no idea where the CLR is on your pic of the old PCB.



There's another resistor to the right of that again on both boards (bottom left when looking component side).  Its that solder spot thats connected to pin 7 on the stomp.  Its a 1k and goes to ground.  If the stomp looks like this...

1 - 3 - 7
2 - 5 - 8
3 - 6 - 9

Then..
1 = Board Out
2 = GND
3 = LED
4 = Jack Input
5 = Jack Output
6 = 1
7 = Mystery 1k > GND
8 = Board In
9 = 4

It looks like its shunting the Effect input to ground via 1k when the effect is OFF.  Which is fine but why bother with the resistor at all?

So what can we do...

I've measured both my transistors and the come in at 199 and 201 hfe if this helps.  
I've noticed that my breadboard sounded quieter when I used a 2N7000 instead of a BS170.
Raising the value of the 3k9 resistor to 4k7 also had positive results.
You can play with the 100k and 2k2 either side of the PW pot and alter its response.

My advice is to play with transistors and find a set that works or alter the PW resistors to taste.

Hope some of this helps lads.

Ciaran.

[tnakatani]

Thanks for the input Ciaran!  I’ll troubleshoot this one on the breadboard and try changing the resistor values to see if that helps.

On Tue, Jul 21, 2015 at 9:06 AM, Ciaran Haslett [via Guitar FX Layouts] <[hidden email]> wrote:

Right lads.... I've finally got to the bottom of this.  So the good news and bad news.

Good news... The schematic and Layout are correct.  I've put mine on the breadboard again and tested it side by side with the original and its identical.  When pushed both oscillate just a touch (there's so much volume).  The decays on both are weird.  Some chirps and phantom notes.  You can actually find examples of these in some Youtube demos.

Now the bad news...

There must be two versions of this PCB cos my one doesn't have a 7k5 tacked to the back.  In fact, if you look closely at the pic you posted tnakatani, you can see what looks like a trace cut under the right leg of that 7k5.  Looks to me like there was as PCB design error that was temporarily fixed with the 7k5 then permanently removed with a PCB revision.

Based on the "newer" PCB I've been using it looks like the 7k5 would have been tacked on in series with the Active resistor and before the input cap so it doesn't look like that will help us.  You may also notice a extra resistor to the right of that 7k5 when looking at the "new" PCB.  Its the CLR on the new board.  I've no idea where the CLR is on your pic of the old PCB.



There's another resistor to the right of that again on both boards (bottom left when looking component side).  Its that solder spot thats connected to pin 7 on the stomp.  Its a 1k and goes to ground.  If the stomp looks like this...

1 - 3 - 7
2 - 5 - 8
3 - 6 - 9

Then..
1 = Board Out
2 = GND
3 = LED
4 = Jack Input
5 = Jack Output
6 = 1
7 = Mystery 1k > GND
8 = Board In
9 = 4

It looks like its shunting the Effect input to ground via 1k when the effect is OFF.  Which is fine but why bother with the resistor at all?

So what can we do...

I've measured both my transistors and the come in at 199 and 201 hfe if this helps.  
I've noticed that my breadboard sounded quieter when I used a 2N7000 instead of a BS170.
Raising the value of the 3k9 resistor to 4k7 also had positive results.
You can play with the 100k and 2k2 either side of the PW pot and alter its response.

My advice is to play with transistors and find a set that works or alter the PW resistors to taste.

Hope some of this helps lads.

Ciaran.

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[Ciaran Haslett]

Hi lads

I randomly came across this today and thought you might be interested.  Someone verified that layout and suggested using a lower gain transistor for Q2.  He used a BC108C at 102hfe and got good results.

Hope this helps.

[BrotherLeech]

I made this yesterday. Plugged it all in - no sound.

Took a look inside again and spotted a short on my 3pdt. Doh!

It sounds ripping. Seems more gated than the woolly mammoth I made. Excellent stuff

[Chris S]

Built this and love it. Does anyone know how I could add a gain/fuzz control to it? I'm using some high output p90s so it ends up being pretty wild. At the moment I've put a turned down volume knob in front of it which is OK but would like to try a traditional gain/fuzz knob. Thanks!!