Need Help with JFET matching fixture

[ljkowal]

Someone out there please tell me the Gate source drain in clockwise order starting at twelve in Mr. Keen's schematic.  I diptraced the schematic and tested 50 fets.  I must have it wrong because they all came up 1.1...v.  I know the DMM leads were backwards and the values should have been -v.  The issue is that I built the PEZ 90 and I get signal at the IC outs but I get no sweep.  Also he says to "tweak" the zeneer value.  What am I trying to match with that.  I bought values from 1v to 6v.

[mdh]

Generally the drain is shown at 12:00 in schematics, the source at 6:00. The gate is the remaining terminal, which on the schematic symbol has an arrow. In my experience it often doesn't matter if you switch the drain and the source, but it does matter if you switch the gate and one of the other pins. My guess would be that you've assumed the wrong pinout for your FET. Try looking up the data sheet for whatever part you have.

I would start with the zener value specified in the schematic (5.1V, I think). Have you played with the trim pot as well? It can make the difference between good sweep and no sweep in a perfectly functioning circuit.

[ljkowal]

Thanx, found part of the problem.  I had gate and source connected on the schematic, then going into the - input of the ic.  I will rebuild my matcher and begin again!  Amazing that a small mention of which terminal has to be specific sent me back to the drawing board and there it was.

[ljkowal]

Matt, if you are still reading this thread I found out that my jfets were a GSD pinout from fairchild.  I needed to reverse them in the layout for the PEZ 90.  It works great.  Only issue now is that the effect doesn't come in until you get 75% around the pot and it is crammed real close (would a different pot like a 1meg stretch it out over the whole pot?).  I used the 500K reverse.  Any thoughts?