Simplistic NJFET RIAA

Well I'm off to bad start

Hi Guys,
As usual, once I touch anything solid state, I screw it up.

What I did:

1. Made one piece of Salas LV shunt from the pdf version (and shown below) for moving magnet 38 V in/28 V out

2. Made one raw supply with 18-0-18 Xfr and a dropping resistor to give 40 V loaded with about 120 mA load (333 ohm resistor)

3. Didn't think to check the unloaded voltage of the raw supply.

4. Hooked up the raw supply to the regulator with a 500 ohm load on output of
regulator (28 V/0.06 A = 0.056 Amp)

5. Got no voltage at output, so checked V/in
Yikes! 55 volts.

6. Checked transistors while still connected on board.
Did a diode check with my DMM Found:

Q1 IRF9540 G to S = OL G to D = OL
Q2 BF245A G to D = continuity G to S = continuity (obviously)
Q3 BC546B B to C = OK B to E = continuity
Q4 IRF9540 G to S = OL G to D = OL
Q5 2SK170 G to D = continuity G to S = Continuity (obviously)
Q6 BC546B B to C = OK B to E = OK
Q7 BC546B B to C = OK B to E = OK

OK, so was I supposed to have V/in 38 V unloaded?

Which three leggy things do I need to replace?

How can I avoid doing this again? :)
 

Attachments

  • Salas LV Shunt.jpg
    Salas LV Shunt.jpg
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diyAudio Chief Moderator
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Salas,
Not sure I will get the re-tracing done today, but here are some photos.
Not the prettiest job, I know.
Thank you SO much.
Doug

The frontal sinks could be saved for normal circa 200mA CCS I guess. So to simplify. But it must work first so to evaluate temps. If you will do a continuity test between CCS Mosfet tab and sink screw, is there any continuity by mistake maybe? I will try to spy with my little eye the pics for connections also.