On Sun, 27 Nov 2011 05:53:46 -0500 JW wrote in Message id:
:

On Sat, 26 Nov 2011 13:45:55 -0500 Jamie
wrote in Message id:
:

JW wrote:

Hi all,

Looking for a datasheet or any info on a FET used in a Keithley 2000
location Q105. The service manual lists it as:
TRANS, N CHANNEL JFET, SNJ132199(SOT-23)

It is marked with three digits "132". Can't seem to find any data at all
on the device.

Thanks.
Yeah, it's tough trying to match up a JET if the pin off voltage is a
critical part of the circuit. Also on top of that, it could be used as a
current source which makes it just as tricky.

I recently repaired a analog PID board that another tech repaired in
the past. They replaced the JFET switch that is in the output that
effectively turns the PID loop on/off. The way it is set in there, the
gate pinch off voltage must fall in the range of 1 to 5 volts(-) and the
tech put a NTExxx replacement in. That was a bad call. The NTE
replacement had a gate pinch off voltage of 5..10V-. This circuit only
had -5 max to play with. Needless to say, it wouldn't switch properly
50% of the time. so wee went shopping for the original replacement,
TO-92 package. guess what, I couldn't find any but I did find one that
had the Gate voltage that I needed and the Idss was even better than the
original.. So we go those. They are like gold these days!

One friendly warning, beware of using NTE parts in critical areas.
They don't always work.

Thanks for that. I think I'll try giving Keithley a call, maybe I'll get
lucky...

Or not. They'll sell me the $2 part, but with a $150 minimum. They claim
this part is made to Keithley spec (!). They also offered the following
info:

"I also show that we purchased these (which were not made to KI spec)
Interfet SJN132280
Fairchild Semiconductor 5149B51374A
Fairchild Semiconductor 5149_NB51374B"

I was unable to find any datasheets or stock on any of them. *sigh*