BS170 can't get them to work at all

[screamersusa]

I've got about 100 each:

J201- dark, clip easy, easy to work with, voltage forgiving from what I can tell.
MFP102 Bright clear, tougher to bias, harder to clip, not too voltage forgiving, strong output. (me like)
BS170...  ? can't get them to work. I tried many pinout variations, disposing of each transistor
              in case I blew it up trying a pinout.  The are apparently fairchilds.
              Are they a pain to get working? How do they sound and perform?
              I heard they sounded a bit mettalic.

Can they be used in a soft clip circuit?

It looks like I will have to mix fet types to achieve my goal. I'm thinking the BS170 might work well in distortion
producing gain stages. 

[kurtlives]

JFETs and MOSFETs sound similar but quite different little devices.

Your going to have to set up your circuit differently to handle the BS170s. It is not a direct drop in replacement for a JFET.

[Toney]

 Here's a hint...

Search for "static sensitive"  

[slideman82]

Are you replacing a Jfet by a BS170? You can't do that unless you have a voltage divider made by 2 resistors (one from G to ground, other from 9V or D to G) and an input cap. Then you have to bias it (adjust 9V to D resistor till you measure 4.5 - 5V from D to ground).

Maybe I have understood wrong, are you uding them in the clipping section? If it's that way, D and G are soldered together, S is the other side of the MOSFET diode.

[screamersusa]

I have a test board with a pair of 201's, a pair of MFP102's with trimpots etc for playing with. I was trying to add a set of bs170's.
I am not trying to sub mosfets for fets. These are stand alone buffers to listen to and get a feel for what works and what doesn't.
I tried few configurations found on the web and all I gould get to pass audio was an attenuator.
Is there any way to test with a vom to ensure the pinout as fairchild apparently has at least 3 different pinouts.
I think that's my main issue.

Toney. I have a nice little antistat mat and armband. 

[rousejeremy]

I have a whole bunch of BS170. I was planning on making an SHO. Not one of them works.

[Toney]

@rousejeremy
I usually prepare the joint by soldering it and then poking a hole through the molten solder with a bamboo skewer. I put the Fet in and add a heat sink and then solder it for as little time as possible. Maybe 1/2 second. bang and out.
They are sensitive little darlings and will pop like a grape unless you are really careful. That on top of the static sensitivity.
You need to handle both these parameters when dealing with them.
Then they are great.

@screamersusa
Nice. Sounds like you are onto that part of it.
Perhaps build as simple, reliable booster such as a Sho type. No special biasing requirements. You'll soon get 'em going.

[DougH]

MOSFETs require a small dc voltage on the gate in order to bias properly, unlike JFET gates which can be referenced to ground. Look up a BS170 datasheet and the "threshold voltage" (Vth IIRC) is specified there. IIRC, it's 2V. I have set this up from 2-4.5v and never had an issue getting a BS170 to turn on. You will need dc blocking via a coupling cap on the input since there is a dc voltage on it, in this case.

[Joe]

I don't know if this helps, but usually the pinout is backwards compared to a normal bipolar transistor.