# calamity fuzz build



## Bobbyd67 (Aug 2, 2020)

Finally got a photo compression app so I can post photos on the forum now xD. 

Here's a build of the calamity fuzz, it's just awesome... If you haven't build it yet, order it now xD. I really love the calamity Jane graphics I did on this one


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## Chuck D. Bones (Aug 8, 2020)

NICE!
A couple of questions:
1) Where did you get your JFETs?
2) Can you please measure and report the drain voltages?

I'm fixing one for a friend and I'm having trouble finding JFETs that work.


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## Bobbyd67 (Aug 8, 2020)

Chuck D. Bones said:


> NICE!
> A couple of questions:
> 1) Where did you get your JFETs?
> 2) Can you please measure and report the drain voltages?
> ...



Yep I used j201 smds from mouser.
Here is the exact link from my order ^^



			https://www.mouser.ca/ProductDetail/on-semiconductor/mmbfj201/?qs=ljbEvF4DwONpFpdsobl6fQ==&countrycode=CA&currencycode=CAD
		


I will try to go down in the basement and mesure the drain on my multimeter ! I would have love to mesure the transistor on my mega328 but it died on me about a week ago


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## Robert (Aug 8, 2020)

Chuck D. Bones said:


> I'm fixing one for a friend and I'm having trouble finding JFETs that work.



Want me to pull the ones off my prototype build and send them to you?


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## Chuck D. Bones (Aug 8, 2020)

Bobbyd67 said:


> I will try to go down in the basement and mesure the drain on my multimeter ! I would have love to mesure the transistor on my mega328 but it died on me about a week ago



I need you to measure them in-circuit on your Calamity board.  It looks like they have to be at the very bottom end of the spec for Vp & Idss to work in this pedal.


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## Chuck D. Bones (Aug 8, 2020)

Robert said:


> Want me to pull the ones off my prototype build and send them to you?


Sure, that would be great!  Thank you, Sir!


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## Bobbyd67 (Aug 8, 2020)

Chuck D. Bones said:


> I need you to measure them in-circuit on your Calamity board.  It looks like they have to be at the very bottom end of the spec for Vp & Idss to work in this pedal.


I am trying to get loose on my end ... but I got a accord with the wife not to tinker on pedals in the day time on weekends xD I am waiting for the opportune time not to get scolded :/


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## Chuck D. Bones (Aug 8, 2020)

Hey, no rush, Man. I just wanted to be clear about what I was asking.  I get it, I have things I should be doing other than pedals too...


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## Bobbyd67 (Aug 8, 2020)

Chuck D. Bones said:


> Hey, no rush, Man. I just wanted to be clear about what I was asking.  I get it, I have things I should be doing other than pedals too...


^^ got them  
Q1 D:7.1v
      S:0.19v

Q2 D:0.9v
      S:0.16v

We're spending the night in the country at my folks house with the kids so packing everything and getting ready in the morning made it pretty much impossible to check the measurements .

I asked my dad for a screwdriver about 15 min ago... Then my wife gave me one of those looks xD then she said .... Tell me you didn't bring a pedal here...

I told her you don't understand !!! It's for Chuck!!! I have to do it! 

On another note, I made a no graphics calamity fuzz a couple of months ago near the start of the pandemic. I sold it pretty quickly and the guy seemed to like it a lot. But now he seems to be having issues with the onset control, gates way to early. I believe that the only jfets I had at the time we're pf5102... :x it was the first time I ever built this circuit and I pretty much figured that's how it's supposed to sound ! Now I believe I might have sold him a faulty unit. I will have to test different jfets to see if it makes a difference but I got a feeling I will be shipping a new pedal to the guy xD


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## Chuck D. Bones (Aug 8, 2020)

Great story!  I appreciate the measurements.  
I tried using PF5102s in the one I'm fixing and they both saturated.  When Vd & Vs are the same voltage, you know it's not gonna work!  In your pedal, Q1 is near cutoff, so Vp is not far from -0.19V.  Q2 is near saturation, but its Vp must also be pretty close to -0.2V.  JFETs are pretty stable over time and temperature, so one or both of the JFETs in the one you sold must be right on the edge of working / not working.  One alternative to hand-picking JFETs is to make the drain resistors select-in-test.  I'm trying to avoid that with the one I'm working on because I want to nail the original sound.  I'd be interested to know if every Unpleasant Surprise that Fairfield builds has the same drain resistors. At the very least, they're cherry-picking JFETs.

Thanks again and enjoy your weekend off!


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