Changing from PNP to NPN

Frequently asked question on transistors: types, substitutions, how to test, use and misuse them.
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trad3mark
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Post by trad3mark »

Hey all,
I'm starting work on a 1969 Boutique Fuzz Face tomorrow, assuming parts arrive. In the vero i have, it works on 2 PNP transistors, but, i have nearly three times the varities of NPN's than i do PNP's. SO, if i wanted to change the circuit to use NPN's instead of PNP's, am i correct in saying that all i have to do is the following:
1. Swap the battery polarity around
- the -ve of the battery will run onto the board (where the +ve originally was) and the +ve of the battery will go to the middle lug of the Input jack
**** I know a bit about the grounding issue with power blocks, but this has a small current draw, with no DC jack, so because it's just battery powered, it won't be a problem.
2. Swap the electrolytes polarity around
- Just like with the battery, they simply have to be swapped that the + goes where the - was etc.
3. Make sure the NPN pinouts (ie, Collector, base, emitter) match up the same way as the PNP
- pretty self explanitory...

IS THAT ALL I HAVE TO DO?

cheers,
tm

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RnFR
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Post by RnFR »

i think that boutique FF is meant for Ge trannies. unless you have NPN Ge's you are going to run into problems. just do the silicon version, it's already NPN.

you got a link to the schem/layout?
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trad3mark
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Fuzz Factory
Aenima/Torn's Peaker (2 in 1 box with toggle switch)
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Proco Rat (Mod to power jack, and input cap changed)
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Post by trad3mark »

i'm going by this one:
Image

it's a PNP version, so if i swap the things around (see 1st post) will it work as NPN?

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UZILSD
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Post by UZILSD »

trad3mark wrote:Hey all,
I'm starting work on a 1969 Boutique Fuzz Face tomorrow, assuming parts arrive. In the vero i have, it works on 2 PNP transistors, but, i have nearly three times the varities of NPN's than i do PNP's. SO, if i wanted to change the circuit to use NPN's instead of PNP's, am i correct in saying that all i have to do is the following:
1. Swap the battery polarity around
- the -ve of the battery will run onto the board (where the +ve originally was) and the +ve of the battery will go to the middle lug of the Input jack
**** I know a bit about the grounding issue with power blocks, but this has a small current draw, with no DC jack, so because it's just battery powered, it won't be a problem.
2. Swap the electrolytes polarity around
- Just like with the battery, they simply have to be swapped that the + goes where the - was etc.
3. Make sure the NPN pinouts (ie, Collector, base, emitter) match up the same way as the PNP
- pretty self explanitory...

IS THAT ALL I HAVE TO DO?

cheers,
tm
Yes, that's all, but I would point out step 1 better. From your description, the original fuzz despite being PNP is negative grounded (usually they're positive grounded, following the tradition). Swapping battery cables will work but be aware that you'll have a positive grounded device. But if it doesn't have a DC plug, it won't be an issue. Use it with battery and it will be OK.

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trad3mark
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Joined: 08 Mar 2009, 15:55
my favorite amplifier: Vox Valvetronix Series
Completed builds: Super Hard On
Fuzz Factory
Aenima/Torn's Peaker (2 in 1 box with toggle switch)
Valvecaster Deluxe (Boost before VC)
Proco Rat (Mod to power jack, and input cap changed)
87% PillowStone
87% GlassJaw
Location: Ireland (Dublin/Waterford)
Been thanked: 1 time

Post by trad3mark »

yeah the fuzz face is one of those pedals with really low current draw, plus, i won't be putting in an LED, so the current draw will stay low. It wont have a DC jack, so it'll be just battery.

Cheers for clearing that up. Parts should arrive on monday, along with parts for my valvecaster. :D SO EXCITED!

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