SMD J201 without adaptors

zeropluszero

Active member
I bought a couple of PCBs.
Cobalt
Desolate fuzz
Chop shop (v3?)
Son of Ben

Cobalt will need adaptors and that's fine, I do have some, I know the others have pads for direct soldering, which I would prefer. My reading suggests not all smd 201s are equal, and I have ordered the actual 201s from here and Digikey so should be legit
Now, can I solder any old 201s to the PCB without testing and the bias trimmers do the fine tuning or do I need to test the 201s somewhat?
 
You should be fine w/ Digikey, just watch for static if it's winter where you are.
I use a wrist ground strap when working with JFETs in the wintertime.
Probably over-cautious, but I really hate having to remount stuff.
 
I always breadboard JFET circuits first and audition the JFETs. The trimmers will get you only so far and some JFETs in some circuits simply cannot be dialed-in with a trimmer.

The Cobalt does not have bias trimmers. It is important that the JFETs are matched to each other and to the circuit. They should at least be in the ballpark. You can read about biasing the JFETs in the Cobalt (BD-2) here. It's very wordy, sorry 'bout that. ;)
 
Last edited:
The Desolate (Fairfield Circuitry Unpleasant Surprise) is very picky about JFETs. Unless you have the right ones, it doesn't work. Fairfield hand-selects the JFETs and that's what we have to to too. You can read about that here.
 
You should be fine w/ Digikey, just watch for static if it's winter where you are.
I use a wrist ground strap when working with JFETs in the wintertime.
Probably over-cautious, but I really hate having to remount stuff.
Good idea. All semiconductors are static sensitive. MOSFETs & CMOS extremely so. Where I worked, we had ESD bench-tops, ESD flooring, wrist straps & annual ESD training. Everything was in ESD bags, including screws, nuts & washers because non-ESD bags are ESD generators. I'm careful at home, but not that careful.
 
I guess I was just asking if any of these I can just solder directly to the smd pads on the boards (which I see heaps of build reports of people doing, are they just getting lucky??) without adding them to adaptors and putting them into my TC1 to test.
if the answer is none that's fine, just wanted to confirm as its way easier for me to just to put them straight onto the PCB.
Summer here in Melbourne.

Thanks for the links Chuck, I'll read them over, I promise I did research these projects, and again, just having seen a lot that have just soldered directly I was hoping I would be able to as well.
 
I guess I was just asking if any of these I can just solder directly to the smd pads on the boards (which I see heaps of build reports of people doing, are they just getting lucky??) without adding them to adaptors and putting them into my TC1 to test.
if the answer is none that's fine, just wanted to confirm as its way easier for me to just to put them straight onto the PCB.
Summer here in Melbourne.

Thanks for the links Chuck, I'll read them over, I promise I did research these projects, and again, just having seen a lot that have just soldered directly I was hoping I would be able to as well.
I made a little jug to test SMD Jfets by holding them very carefully onto 3 solder points. It worked but was a right pain.
 
Back
Top