VP3203 substitute

[spi]

I see this transistor being used for what I assume is polarity protection.
I'm thinking a 2n7000 could be a viable substitute?

 

[Cybercow]

Not really. The 2N7000 is an "N Channel" device. The VP3203 is a "P Channel" device. That protection circuit calls for the P channel device.

 

[spi]

Hmm, I don't see any p-channel mosfets from Tayda in a T-92 package. Maybe I should just put a diode across D to S there instead, and leave out the resistor.

I've never seen ferrite beads in circuits before either. This is an odd one.

 

[jimilee]

I see this transistor being used for what I assume is polarity protection.
I'm thinking a 2n7000 could be a viable substitute?
View attachment 32997

It’s mosfet and the same pinout as the 2n7000, just flip it, I believe. It’s DIY, give it a shot.

 

[Cybercow]

It’s mosfet and the same pinout as the 2n7000, just flip it, I believe. It’s DIY, give it a shot.

The MOSFET power supply protection scheme is not like flipping BJTs in dirt circuits. Can't use an N-channel MOSFET in the positive lead for protection. It must be a P-channel one. If it was a negative supply (positive ground) then an N-channel device is called for. If an N-channel MOSFET is used in the ground (negative) lead of the power input, it would mean that the supply would need to be fully isolated and could not share ground with any other pedals.

 

[jimilee]

The MOSFET power supply protection scheme is not like flipping BJTs in dirt circuits. Can't use an N-channel MOSFET in the positive lead for protection. It must be a P-channel one. If it was a negative supply (positive ground) then an N-channel device is called for. If an N-channel MOSFET is used in the ground (negative) lead of the power input, it would mean that the supply would need to be fully isolated and could not share ground with any other pedals.

See, now I learned something, thank you. I guess my point was, don’t be afraid to experiment. Breaking it is the easiest way to learn to fix it yourself.

 

[music6000]

BS250P if you can find one???

 

[Cybercow]

Most any of these would be suitable from Mouser.com - they're in a TO92 package.

The IRFD9020 (also from Mouser.com), will work, but it's in a small, chip-like package.

 

[benny_profane]

You could also just use a 1n5817 (drain to source) and omit R1 if you don’t want to bother with the mosfet. The mosfet scheme is more efficient w.r.t. current and doesn’t incur the same Vf loss, though.

You could also jumper the ferrite bead. It’s there to suppress high frequency noise.

 

[spi]

Most any of these would be suitable from Mouser.com - they're in a TO92 package.

The IRFD9020 (also from Mouser.com), will work, but it's in a small, chip-like package.

I appreciate the links, but I'm probably not going to initiate an order to mouser for a < $1 part. I was hoping to find something at Tayda, because I do have an order ready to place there.

I think I'll socket it, cross it with a diode, and maybe later if I ever need to order more stuff from mouser I can pick one up.