J201 Possibly Not Real

[joelorigo]

It came up in a Troubleshooting thread I started that the J201 transistors I have been using might not be real. I have used these in s few builds and the pedals have worked, so I guess the issue is that the transistors I have been using might be not performing to the actual specs. Are these real?

 

[jessenator]

If it quacks like a duck? I would say you isolate the variables and test the parts—i.e. if these are part of the buffer (haven't seen the troubleshooting thread), test them apart from the signal transistors.

Your pic on the left looks etched and the one on the right looks printed—both thinner than I've seen, which isn't always sure-fire. Where did you acquire them?

Here are some pics of genuine NOS Fairchild TH jobbies from my stash:

https://imgur.com/a/y26s4Of

I don't recall when Fairchild / ON Semi discontinued TH versions of their JFETs but I wonder if there's a table of date codes that lead to fakes somewhere out there as well.

 

[joelorigo]

They pictures are the same item, etching with printing in the grooves. I got them from Guitar PCB. The troubleshooting thread turned out to be a backwards diode but someone pointed out that the J201 maybe didn't look legit. For my M800 I bought the PedalPCB pre-soldered SMD ones so, I'm wondering if I should get some more of those and go back to whatever builds I have used the above ones and replace.

 

[spi]

A couple years ago I got a batch of j201s and 2n5457s from Guitar PCB. All the j201s were in spec. The 2n5457s worked, but were out of spec.

I'm guessing you're probably ok. No reason to replace them in working pedals. Especially if they biased correctly.

 

[Cybercow]

They pictures are the same item, etching with printing in the grooves. I got them from Guitar PCB. The troubleshooting thread turned out to be a backwards diode but someone pointed out that the J201 maybe didn't look legit. For my M800 I bought the PedalPCB pre-soldered SMD ones so, I'm wondering if I should get some more of those and go back to whatever builds I have used the above ones and replace.

If you got J201 JFETs from GuitarPCB, they are legit. I've gotten dozens and dozens from them and they always checkout.

 

[paulbarrette]

If you got J201 JFETs from GuitarPCB, they are legit. I've gotten dozens and dozens from them and they always checkout.

1+
I am pretty confident that guitar pcb sells real legit parts. I have ordered a bunch from him.

Pb

 

[chris.knudson]

I've bought J201s off of Amazon that I am pretty sure aren't legit, but they do work and seem to be in spec. Having said that, I've had enough problems with bogus parts that I just don't trust them. I've started switching to SMD parts from Mouser that I am pretty confident will work as expected.

 

[HamishR]

I have a heap of legit J201s I got from Small Bear and they still cause issues by being all over the place with biasing. I seem to have very few problems with 2N5457s, 2N5458s, 2N5952s and J113s, but J201s are always a pain. The 2N**** JFETS I have were all from Mouser.

 

[joelorigo]

I just used one in the Sushi Box King Nothing and there is no biasing. Here is what the TC1 said when I measured it before insertion.

Idss=0.36m
Id=0.22mA
@Vg=150mV
ID=0.00MA
Id=644mV

Does any of that tell us anything?

 

[szukalski]

It's a bit of a crap shoot, even with legit transistors. Some pedals may be built using one manufacturer with a cluster around certain values within the range of the spec, where-as another manufacturer may have values clustered around the other end of the spec range.

SMD is better in this respect from my experience.