Salas SSLV1.3 UltraBiB shunt regulator

[gaszto]

Vbe on Q1 is 545mV.
I don't have other type Pmos, but I have two more FQP. I remove the current M1 and try to check with my component tester.



Could be some other component wrong what is killing M1 immediately after replacement?

 

[Salas]

Also look on Q1 Q4 with a magnifier, the way they are printed BC327 looks similar to BC337 to the naked eye. Confirm they are BC327 populated indeed. Static can kill Mosfets either by handling or not earthed iron.

 

[gaszto]

Q1 and Q4 are BC327 clearly visible. I desoldered M1 the component tester recognizet P-E-MOS C=348pF Vt=4.5V

 

[gaszto]

Does the component tester recognize the previous FQP you replaced?

Yes, meantime I checked the other two FQPs with the tester, and the measured values are similar 5% differences only

 

[Salas]

Standard hundreds of times built board and a big mystery. Weird, very weird. Change Q1 for good or bad. If you don't have another BC327 put a BC560 or any other CBE pins PNP.

 

[Salas]

R1 is 4.9 Ohm indeed?

 

[gaszto]

Ok, I'll change Q1.


R1 is currently 4.8Ohm, but I have 3.9Ohm. (In my own version of UltraBiB I used 3.9Ohm)

 

[Salas]

See with the continuity tester (DMM buzzer) if by any chance some connection or pad is broken in the first block of circuitry around M1. We need it to have few Volt Vgs. 11.5V is essentially 9VAC rectified. Passes right through to the output now.

 

[gaszto]

I replaced Q1 to a new one, and I put M1 back. Same 11.5V Out and 11.5V between leg 1-3 of M1


still no voltage drop on R7 and the led light is low.


in the post # 2543 the problem was exactly the same.

 

[Salas]

Do you have JFETs to replace?

 

[gaszto]

Yes, I have a lot. Replace all of them?

 

[Salas]

Yes just in case

 

[gaszto]

Yeeeah.It's working!!!!!! The only part what wasn't replaced the Q4 and the resistors. So one of the JFET was faulty

 

[Salas]

At last!

 

[Salas]

Also has no ripple on output now? (Use the short ground probe nose spring).

 

[gaszto]

I have a lot of noise. I used very similar probe.

 

[Salas]

Power down the reg and put the probe at the same place as before. Anything changes?

 

[gaszto]

Yes. After power down, the noise disappeard.

 

[Salas]

Also use 10X setting on probe and scope because at 1X a usual probe has less than 10MHz bandwidth.

 

[Salas]

Yes. After power down, the noise disappeard.

But no 100Hz saw-tooth ripple and voltage is adjusting down to 5V DC out now?