Question regarding Geofex improve Jfet tester and 2N5952's.

[Milotic]

I recently ordered a large number(40-50) of 2N5952's and i am trying to get a matched sets for my Phase90.
To test it i am using a Geofex Improved JFET tester.
With the DMM i am getting voltage reading between -0.02v-4.17v, when nothing is plugged in.
When some spare trannies (2N5952) are plugged in, i am getting values of -1.36v to -1.67v.

This is the first time i am attempting to match Fets, so i am just wondering if i am doing it correctly.
Also what values should i be aiming for with the 2N5952, to get the most beautiful sweepy wavey tones from the phaser?
Sorry if this seems abit silly.

Regards.

[Govmnt_Lacky]

My 2 cents...

SOCKET ALL OF THE TRANSISTORS IN THIS CIRCUIT!

I have used FETs matched from -1.40 to -1.90. They all sounded great. The most important thing to remember is to get 4 of them (for a Phase 90 circuit) AS CLOSE TOGETHER as possible in voltage. Usually, you do not want any of the 4 in the set to be more than 0.1V apart. That is the threshold that I use and it has worked great so far. 

For example:

FET 1 = -1.42
FET 2 = -1.45
FET 3 = -1.44
FET 4 = -1.37

The greatest seperation between voltages is .08 (between FETs 2 and 4) so this is GOOD! 

Also, the zener diode in the circuit is important as well. I have always used a 5.1V zener and have not had problems however, I have read that it could matter and you might use a 4.7V zener instead. SOCKET this as well just in case.

Good Luck 

[Milotic]

Thanks for the reply.

For the FETs i am going to attempt to find a perfect set of 4.  Hopefully it will sound beautiful.
As for the Zener, i can't find any sockets that can actually fit it.  The Zener diode leads are too big for the standard sockets i use for trannies and ICs.
I am assuming it has something to do with the sweep?  How do i choose the right value?

[Govmnt_Lacky]

For the FETs i am going to attempt to find a perfect set of 4.  Hopefully it will sound beautiful.

The closer the values..... the better the WOOOOOOOOOOOOOSSSSSSSSHHHHHHHHHH 

As for the Zener....  How do i choose the right value?

Like I mentioned above... I ALWAYS use a 1N4733 (5.1V zener) however, I have read that some people have used different values (a la 4.7V)
My advice is to start with a 5.1V. If you are having issues, then desolder and try a 4.7 but I am guessing that if you match the FETs well enough, you won't need to swap them.

Good Luck 

[Milotic]

got the bulk 2n5952 today and found 5 of them matched at -1.56v, used them and wow.
Out of the 44 only got 1 trannies that didn't match.  most of them are perfect matches or a 95-100% match.
Time for ebay!

Thanks Govmnt_Lacky