Fuzz Factory NPN AC127 - PCB n Layout Inside

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tiococo
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Post by tiococo »

Guys.

I have at my disposal a lot of AC127s so I decided to make a negative ground version of the fuzz factory

Here is the schematic

Image

Please check if everything is okay and I hadn't made any mistakes...
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fuzzfactory pcb.pdf
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fuzzfactory layout.pdf
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Post by DrNomis »

I just had a look at the schematic, and it appears to be all good.... :D
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Post by RnFR »

does the FF have that power filtering cap? seems to me, that would quell any oscillations.
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Post by adielricci »

The output pot has to be in series with R6, or you have to add another 5K1 resistor in series with it and capture the output from their junction, maybe with a 100K pot.

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Post by adielricci »

RnFR wrote:does the FF have that power filtering cap? seems to me, that would quell any oscillations.
In that place, there is no problem, and I would even add another 100n cap in parallel with it, to kill any high frequency transients.

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Post by DrNomis »

I just noticed something, there should be a coupling cap between the output control pot and the rest of the circuit, the cap can be anything from 10nF to 100nF, also there should be a 470 Ohm resistor going from the 5.1K collector resistor (R6) of Q3 to +V..... :D
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Post by ckyvick »

How would it sound? Wouldn't you want to make it positive ground like the reverse fuzz factories?
http://t1.gstatic.com/images?q=tbn:ANd9 ... DCBS-g&t=1

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Post by tiococo »

Guys. I Have updated the schem.

One is the the OEM configuration
Here
Image

And here is the normal Fuzz Face configuration
(A Npn Fuzz Face with a buffer and pots instead od resistors)
Image


Ok, as I see, the OEM Factory doesn't have the 470 Ohm resistor. Thats no problem because the pot acts as a voltage divider when the pot is not maxed. But what happens when it's maxed? The center wiper goes to 9v, that DC blocked by the cap will carry audio?

The second configuration seems more logical (and familiar) to me. But I want to preserve the circuit as original as I can.

opinions?

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Post by DrNomis »

tiococo wrote:Guys. I Have updated the schem.

One is the the OEM configuration
Here
Image

And here is the normal Fuzz Face configuration
(A Npn Fuzz Face with a buffer and pots instead od resistors)
Image


Ok, as I see, the OEM Factory doesn't have the 470 Ohm resistor. Thats no problem because the pot acts as a voltage divider when the pot is not maxed. But what happens when it's maxed? The center wiper goes to 9v, that DC blocked by the cap will carry audio?

The second configuration seems more logical (and familiar) to me. But I want to preserve the circuit as original as I can.

opinions?

The OEM Factory configuration will work if you wire up the volume control pot so that when it's maxxed out( turned fully clockwize), the wiper is at the junction of the 5.1K (R6) resistor and the volume control.... :D
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Post by tiococo »

that's what I thought :D

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Post by tiococo »

Corrected.

Done.

I'll verify the pcb and post what happens later.

Regards!
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Post by Loss1234 »

HMMM...I built this as per the schematic (both ways) and with a variety of NPN's I can not for the life of me make it oscillate like the PNP version I have built (with a variety of transistors)

when the OP built this, did it oscillate properly?

thanks

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Post by Scruffie »

Loss1234 wrote:HMMM...I built this as per the schematic (both ways) and with a variety of NPN's I can not for the life of me make it oscillate like the PNP version I have built (with a variety of transistors)

when the OP built this, did it oscillate properly?

thanks
Yeah the Fuzz Factory oscillates because it's a positive ground circuit reversed (positive ground circuits don't work quite right reversed alot of the time)... if you fix it to negative ground I can see why it wouldn't.

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Post by soggybag »

Has anyone built this? I was just thinking about trying to do a NPN Fuzz Factory and low and behold google reveals this thread.

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Post by tiococo »

I built 3 boxes with this layout. So its verified

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Post by abc1234 »

The schematic is down and having read through the discussion it seems it wasn't updated when the corrections were made.

Can anyone upload a correct schematic or simply explain how to build an all-NPN negative ground Fuzz Factory?

e.g. Is it simply a case of using the Stab pot to +9v starve the collectors of all the transistors (as opposed to +9v starving Q1's collector and the emitters of Qs 2&3 in the stock Factory) and changing the volume control setup?

Here's a schematic of the stock Factory:

Image

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Post by soulsonic »

abc1234 wrote: 10 Jul 2020, 13:20 The schematic is down and having read through the discussion it seems it wasn't updated when the corrections were made.

Can anyone upload a correct schematic or simply explain how to build an all-NPN negative ground Fuzz Factory?
If you want it to oscillate, you shouldn't do all NPN. As Scruffie stated earlier, the oscillation is inherent to using PNP transistors. If you swap the circuit around to make it all NPN, it won't behave the same way.

If you wanted to make a non-oscillating Fuzz Factory for some reason, you can stick with PNP and add power supply decoupling to the two PNP stages. But I think doing all this cleaning up to the circuit takes away its charm and then you may as well be making a Tone Bender mk2.
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