# Transistor question



## dlazzarini (Aug 1, 2020)

I’m looking up some equivalents to 2 obsolete transistors. Seems I get no concrete answers plus I still don’t know enough about transistors to use the info I’m finding. Can anyone tell me if there are equivalents to a 2n5551 and an mps2222a. I’d appreciate any suggestions. They’d be for a noise gate if needed


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## BurntFingers (Aug 1, 2020)

If you match the pinouts you've got an equivalent that will function in the circuit, but will most likely have different hfe characteristics. Best bet is to socket the q pads and roll transistors until you find a set you like. 

They come and go as manufacturers phase out obsolete models. But if it's just a regular npn transistor with a bce layout, you've got about a million choices.

Check the data sheets and see what's going on with the pinouts. The MPS series and 2N series are ubiquitous in the pedal world.


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## dlazzarini (Aug 1, 2020)

Tha


BurntFingers said:


> If you match the pinouts you've got an equivalent that will function in the circuit, but will most likely have different hfe characteristics. Best bet is to socket the q pads and roll transistors until you find a set you like.
> 
> They come and go as manufacturers phase out obsolete models. But if it's just a regular npn transistor with a bce layout, you've got about a million choices.
> 
> Check the data sheets and see what's going on with the pinouts. The MPS series and 2N series are ubiquitous in the pedal world.


thanks for the info


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## Nostradoomus (Aug 2, 2020)

MPS2222a = 2n2222a = PN2222a

Different manufacturer, same thing.

2n5088 will replace most any generic NPN transistor you can shake a stick at, 2n5551 is no exception. Only thing special about those is they can handle 150 volts.


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## dlazzarini (Aug 2, 2020)

Nostradoomus said:


> MPS2222a = 2n2222a = PN2222a
> 
> Different manufacturer, same thing.
> 
> 2n5088 will replace most any generic NPN transistor you can shake a stick at, 2n5551 is no exception. Only thing special about those is they can handle 150 volts.


Thank you


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## dlazzarini (Aug 2, 2020)

Nostradoomus said:


> MPS2222a = 2n2222a = PN2222a
> 
> Different manufacturer, same thing.
> 
> 2n5088 will replace most any generic NPN transistor you can shake a stick at, 2n5551 is no exception. Only thing special about those is they can handle 150 volts.


I have another question in relation to these 2 transistors if you don’t mind. I’m trying my hand at tracing a circuit. My isp Decimator. If one transistor can take the place of most other generic transistors, why bother using 2 different ones in the the circuit? Why not just the same ones.


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## music6000 (Aug 2, 2020)

Maybe you should consider this option:
I paid $32.00 AU & FREE SHIPPING!
Well worth Viewing!





It's a Clone of the ISP


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## BurntFingers (Aug 2, 2020)

dlazzarini said:


> I have another question in relation to these 2 transistors if you don’t mind. I’m trying my hand at tracing a circuit. My isp Decimator. If one transistor can take the place of most other generic transistors, why bother using 2 different ones in the the circuit? Why not just the same ones.



They all sound different and perform differently in circuits.


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## dlazzarini (Aug 2, 2020)

music6000 said:


> Maybe you should consider this option:
> I paid $32.00 AU & FREE SHIPPING!
> Well worth Viewing!
> 
> ...


Thanks for the reply but I don’t really need another one. It’s mostly a learning tool. I’m trying to trace mine and teach myself how to make a schematic and try to breadboard it.


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## Vildhjuggah (Aug 2, 2020)

I bought the rowin one and it (at least mine) was shitty.
Not "tight" and also since Iran it after my boost/od, particularly my "integral preamp" or "dwarven hammer" ), when I palm mute/chug it would actually clamp down on those so almost act like a compressor that was clamping down/farting out.
Granted I could've done more testing in different spots, but in the end I moved it to my bass board, then built the "muzzle" for my guitar board and its amazing.


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## dlazzarini (Aug 2, 2020)

Vildhjuggah said:


> I bought the rowin one and it (at least mine) was shitty.
> Not "tight" and also since Iran it after my boost/od, particularly my "integral preamp" or "dwarven hammer" ), when I palm mute/chug it would actually clamp down on those so almost act like a compressor that was clamping down/farting out.
> Granted I could've done more testing in different spots, but in the end I moved it to my bass board, then built the "muzzle" for my guitar board and its amazing.


I made 2 muzzles. The best by far.


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## Chuck D. Bones (Aug 2, 2020)

dlazzarini said:


> If one transistor can take the place of most other generic transistors, why bother using 2 different ones in the the circuit? Why not just the same ones.


You might also ask: "Why do the semiconductor manufacturers make hundreds of different transistors?"

BurntFingers is on the right track.  Some transistors are optimized for specific applications.  Low noise, high voltage, high frequency, low saturation voltage, high power, high gain, etc.  Back in the Paleozoic, pedal builders made do whatever they could get.  These days, Boutique builders either use "vintage" parts (for mojo), common parts (for easy procurement), or obscure parts to differentiate their version of the Fuzz Face from the other 200 Fuzz Faces.

Some circuits are very sensitive to the particular transistor used, others are pretty forgiving.  Like BF said, you can always install sockets and try a few.  Just make sure the pinout, polarity and technology are compatible with the board.


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## dlazzarini (Aug 3, 2020)

Thanks Chuck. It’ll be on a breadboard if I make it that far on my tracing adventure. “Paleozoic”. That’s a good one.


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## Chuck D. Bones (Aug 3, 2020)

That's a shit-ton of parts to breadboard.  Some of those ICs may only be available as surface-mount, which will add another layer of "fun" to a breadboard.


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## dlazzarini (Aug 3, 2020)

Chuck D. Bones said:


> That's a shit-ton of parts to breadboard.  Some of those ICs may only be available as surface-mount, which will add another layer of "fun" to a breadboard.


Lol. I love a challenge. If you recall my very first breadboard project was the Betty Boost. It gave me a headache and an upset stomach but I got it.


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## Chuck D. Bones (Aug 3, 2020)

Ya know, just because a breadboard has 830 contact points, doesn't mean you have to fill up every one.


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## dlazzarini (Aug 3, 2020)

Lol. Mine has 3 boards put together. Thanks for always helping out and adding your insight Chuck. It’s greatly appreciated


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