Friday, April 12, 2019

Lambda Diode using surface mount devices.

This one would be a lot easier for someone with good young eyes, I'm using a microscope and still having trouble handling  the parts BUT for those brave at heart it could be worth the effort. I'm using a 2SK2539 and a MMBF J175. Lay one on the table right side up and glue the other on top of it up side down. You can see the step, one component is wider than the other.

I flipped them over. The smaller is on bottom and we can't see the step. Notice the writing doesn't show on either side. if it did my parts would not be match properly.
The sources tie together and gate to drain and gate to drain.
Seems easy enough until the soldering begins?

That solder job just about licked me.
If you have leaded JFETs on hand I wouldn't recommend the surface mounts. They do make a smaller package but are a pain to solder. It probably would be better to solder them to a chip of board and use jumpers. It would make a neat package if the JFETs were put in a drop of epoxy.
I just laid the leaded JFETs face to face and made the center connection the positive lead. Check with the ohmmeter and find a low reading to the center pin. (about 40 ohms.) Spare that connection. The remaining connection is the Negative lead. Put it in series with a coil and a 3 volt supply and it sings.

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