Fat pants jr

[Jmilla]

Built up a fat pants junior. Checked my wiring  and power with dmm. Tried to bias the get and can only get between 7-8 volts. Any idea what this could be? Will upload pics in a bit.

[jubal81]

What JFET did you use and where did it come from?

[Jmilla]

Smt  jfet on an adapter board from Paul's store. Jfet from his store as well. How easy is it to fry the fet while soldering? I'm a noob with smt.

[midwayfair]

Built up a fat pants junior. Checked my wiring  and power with dmm. Tried to bias the get and can only get between 7-8 volts. Any idea what this could be? Will upload pics in a bit.

Post the voltages on all three pins of the transistor, and on both sides of D2 -- D5.

[Jmilla]

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[Jmilla]

On further readings at the drain I get mostly between 11-14 v and the trimmer makes no difference


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[Jmilla]

Does this seem like the jfet is the issue?


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[Jmilla]

Changed the jfet our for one from small bear.  Different readings again. Have no idea what is going on with it.

Ic voltages match reference from build doc

[midwayfair]

You need to put the black probe on ground. I'm not sure exactly how you were measuring the latest batch.

Your FET's source should not be at ground. Look at the schematic and you'll see that there's a resistor there. It should be at least a couple volts. I might be misreading your first picture, but it looks like you only posted the drain voltage there.

[Jmilla]

Black lead was to ground. Source and gait were both 0. Second pic was with a different J201 from small bear.

[Jmilla]

does This seem like something is shorted somewhere or does this seem like a bad part? Also why would the trimmer have no effect on the drain voltage? Does this se m like a bad trimmer? Every time I hook power up with my one spot I get different readings at the j fet.

[midwayfair]

You are showing negative voltages on your second picture. Swapping a FET or dinking around with parts on a board does not suddenly cause your power supply to reverse its polarity. You measured your voltages wrong. Please fix that and repost them.

If you haven't reflowed your solder joints everywhere you need to do that as well.

[Jmilla]

You are showing negative voltages on your second picture. Swapping a FET or dinking around with parts on a board does not suddenly cause your power supply to reverse its polarity. You measured your voltages wrong. Please fix that and repost them.

If you haven't reflowed your solder joints everywhere you need to do that as well.

Thanks Jon sorry for the annoying posts. I think I ended up messing up my connection to ground on the power jack and breaking a solder joint with trying to bias this thing. Frustrated with my skills. I really appreciate the patience and help! Will reflow some possible connections and try again tomorrow. Sorry again for being the annoying guy

[midwayfair]

Thanks Jon sorry for the annoying posts. I think I ended up messing up my connection to ground on the power jack and breaking a solder joint with trying to bias this thing. Frustrated with my skills. I really appreciate the patience and help! Will reflow some possible connections and try again tomorrow. Sorry again for being the annoying guy

I'm not annoyed. I'm sorry if it sounded that way. But maybe measuring again before insisting that you did it right would have been the right call.

[Jmilla]

Got this thing working!