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Old 3rd April 2012, 09:23 PM   #1
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Default fuzz face help

Hi. First post on this site, so bear over with me.

I recently buildt a bc108 fuzz face based on the schematic on this site:

Fuzz Central -- Arbiter Fuzz Face

Everything seems to work, it it cuts out if I play a little soft, between notes or if I turn the volume down just a little. Does anyone know what's wrong or what errors to search for?

(switch is wired as suggested here:
http://www.diystompboxes.com/smfforum/i ... _next=prev
There's also a led with a 1 k resistor that doesn't appear in the schem), all the ground points are soldered together and to common ground.)
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Old 4th April 2012, 04:24 AM   #2
Simon B is offline Simon B  United Kingdom
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That led will be drawing about 7mA, so if you're running from a battery you'll dramatically shorten its life.

The second link you give:

http://www.diystompboxes.com/smfforum/i

doesn't work for me, so I can't see how you've wired it.

Assuming that's all ok though, and that you haven't got a defective component, all I can think of at the moment is that you've perhaps got a wiring error - how is it constructed? Pcb? Vero/Strip board? Dead bug?

Maybe a close up photo would help, if you can take one and post it? Better still two photos, one of each side of your board, assuming your using one.

Check and re-check that you've got the right connections between the right value components in the right places and that you've got E, B & C correctly oriented on your transistors.


Last edited by Simon B; 4th April 2012 at 04:31 AM.
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Old 4th April 2012, 04:42 AM   #3
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Which one did you build? There are 3 different schematics there. What voltages are on collectors of transistors? On bases and emitters? It would help to help you to diagnoze your problems.
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Old 4th April 2012, 08:52 AM   #4
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Hi, thanks for the feedback guys.

@Simon B: Not running a battery (using a t-rex fuel tank). I assume you mean the link doesn't work, try this:
True Bypass - Why not ground the input AND the output?
the switch seems to work fine. It's constructed using a vero board (i think thats it, the type with holes and no strips a.k.a. test board) and I'm quite confident the solderjoints are good, though I woun't rule anything out at this point, and shouldn't that make it cut a bit at random?

@Wavebourn: I buildt the second one on the page, the NPN one, using bc108 tranies. Someone at another site suggested it might be 8.2 biasing resistor on Q2 being wrong? I'll see if i can't get some measurements when I get home.
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Old 4th April 2012, 12:39 PM   #5
Simon B is offline Simon B  United Kingdom
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Seriously,

if you can, post pictures.
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Old 4th April 2012, 01:07 PM   #6
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Quote:
Originally Posted by eugene martone View Post
Hi. First post on this site, so bear over with me.

I recently buildt a bc108 fuzz face based on the schematic on this site:

Fuzz Central -- Arbiter Fuzz Face

Everything seems to work, it it cuts out if I play a little soft, between notes or if I turn the volume down just a little. Does anyone know what's wrong or what errors to search for?

(switch is wired as suggested here:
http://www.diystompboxes.com/smfforum/i ... _next=prev
There's also a led with a 1 k resistor that doesn't appear in the schem), all the ground points are soldered together and to common ground.)
Hi
I guess that the battery is sagging because of high current taken from it...
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Old 4th April 2012, 04:35 PM   #7
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Check the bias - sounds like it's gating from a mis-bias.

True the LED is sucking more current than the FF, it's still not likely a low battery. Do check it with your other measurements.
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Old 4th April 2012, 06:30 PM   #8
Simon B is offline Simon B  United Kingdom
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It's not batteries guys, as he says above, he's using a power supply.

Voltages and pics will be the way to solve this one I think, so it's up to you Eugene. Maybe show us your vero layout too if you can.
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Old 4th April 2012, 06:41 PM   #9
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Quote:
Originally Posted by Ronsonic View Post
Check the bias - sounds like it's gating from a mis-bias.

Right. That's why measurements are needed.
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Old 10th April 2012, 08:41 AM   #10
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Quote:
Originally Posted by Simon B View Post
It's not batteries guys, as he says above, he's using a power supply.
right

maybe check 100k to base Q1 connection? Or input cap is leaking?
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