My BSIAB is acting up, help...............

[Xavier]

I have just finished building it and I'm going crazy when trying to debug it............. I have gone through all the usual procedures..............after checking everything I'm not able to make it work. Sounds loud but all I get is splatter.........no gating effects.

I'm mixing 2N5457 and j201 as per Ed Guidry's schematic

Here are my voltage readings, as per Gauss Markov schematic:

Q1
D 8,75V
S 4,5V
G 5,05V

Q2
D 8,75V
S 4,25V
G 4,15V

Q3
D 4,5V
S 1,14V
G 0V

Q4
D 5,05V
S 0,63V
G 0V

Q5
D 4,3V
S 0,05V
G 0V

I'm checking the source and gate resistors from Q4 and Q5 and everything looks correct.

What could it be? This circuit was my first build and after 4 years it's still a bad mofo to debug...............

[Govmnt_Lacky]

It looks like your problems are with Q1 and Q4. This may be already known, but according to JD Sleep's voltage readings your voltages on Q1 are about 4-5 volts TOO HIGH and your voltages on Q4 are 3-4 volts TOO LOW.
You may want to take a fresh look at the board and confirm the transistor part numbers and lead orientation on the board. If those are right, then look around those transistors for bad components, solder runs, etc.


Good Luck!

[Zben3129]

Did you socket the JFETs? They are very easy to toast.

Also, did you check the pinout of the actual JFET you have (manufacturer specific)? I'm talking about the pinout for a Fairchild 2n5457, or a National Semiconductor 2n5457, or a...

Sometimes the pinouts vary between manufacturers. Do this for both J201 and 2n5457


Zach

[Xavier]

I finally gave up and used the components for other builds. Nevertheless Daniel Schwarz has posted a rather interesting design which includes a BSIAB, plus a TS-like circuit in front. This I'm going to build soon