Author Topic: zombii (fuzz factory) no oscillation  (Read 3365 times)

jolly1423

zombii (fuzz factory) no oscillation
« on: December 03, 2011, 09:21:01 PM »
This is my first experience with ge tannies. My zombii works and gets ok gain if it's set just right but the sustain doesn't seem to be there and I can't get any kind of oscillation out of it. I used a 68hfe for q2 and a 113 for q3. I have no idea where to start tweaking, was hoping someone could point me in the right direction... I don't have any buffer in front of, just straight into the amp. I've tried humbuckers and single coils into a traynor ycv80 and a blackheart handsome devil.

jolly1423

Re: zombii (fuzz factory) no oscillation
« Reply #1 on: December 08, 2011, 09:22:35 PM »
Do I need a higher gain on q2 or can I adjust a resistor to tweak the gain?

jolly1423

Re: zombii (fuzz factory) no oscillation
« Reply #2 on: December 08, 2011, 09:32:44 PM »
Or is a bias issue? I haven't had any experience with biasing yet. What I got in researching for a fuzz face is you bias at the collector of q2. Does that hold true for this circuit too?
http://www.madbeanpedals.com/projects/index.html
It's the zombii (I can't link to the pdf directly)
Thanks for any help!

PRR

Re: zombii (fuzz factory) no oscillation
« Reply #3 on: December 09, 2011, 12:42:21 AM »
> I can't link to the pdf directly

http://www.madbeanpedals.com/projects/Zombii/docs/Zombii_ver.5.pdf

Please review the debugging page.

Did you use a pre-made PCB or roll-your-own?

What voltages on each transistor?

This wacky zombii has an added complication, the "STAB" control. First check with this turned one extreme, then the other extreme.
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jolly1423

Re: zombii (fuzz factory) no oscillation
« Reply #4 on: December 09, 2011, 10:55:50 PM »
Thanks for the direction (i.e. debugging page) and sorry my info was so incomplete! I used madbeans pcb and made no mods or part swaps. These are the ge trannies I used-http://transistor-spravochnik.ru/description/2sa221/8484
Voltages-
Q1 c-1.75 b-.68 e-0
Q2 c-8.48 b-8.78 e-8.85
Q3 c-8.38 b-8.48 e-8.83
9v in 8.86
I watched and played along with the setting using in the pro guitar shop demo video of the fuzz factory so I went through all the settings and played with the full range of all the controls. It just really lacks gain and sustain and I can't get anything remotely close to feedback or oscillation.

PRR

Re: zombii (fuzz factory) no oscillation
« Reply #5 on: December 10, 2011, 02:27:29 AM »
Does turning the "COMP" and "GATE" pots change Q3 collector voltage?

Frankly, as I understand the circuit, there's THREE "bias" adjusters (GATE COMP and STAB) and I don't know how to even get it to "work", much less work as desired. Much less debug it for wiring errors.
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jolly1423

Re: zombii (fuzz factory) no oscillation
« Reply #6 on: December 10, 2011, 06:42:58 AM »
I'll check that out tonight. Does the '0' on the Q1 emitter seem normal? I thought that was odd...

PRR

Re: zombii (fuzz factory) no oscillation
« Reply #7 on: December 10, 2011, 10:03:50 PM »
> Does the '0' on the Q1 emitter seem normal?

Look at schematic, or peep the PCB. Q1 emitter is directly connected to ground.
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jolly1423

Re: zombii (fuzz factory) no oscillation
« Reply #8 on: April 13, 2013, 09:08:07 PM »
Just wanted to let you know I finally got this working. I just needed a different set of ge's. Sounds awesome now! Thanks for the tips. :)