Salas SSLV1.3 UltraBiB shunt regulator

[Salas]

Jim hi,

Check the BC transistors and the LEDs with the DMM's diode mode. Without removing them.

 

[JKiriakis]

Hi Salas -

DMM = UNI-T UTI39C Diode mode

BC transistors on negative reg:

Q1 B:E 0.059 B:C 0.559 / reversed leads B:E 0,059, B:C 0.597
Q2 B:E 0.266 B:C 0.634 / reversed leads B:E 0.266 B:C OL
Q3 B:E 0.691 B:C 0.634 / reversed leads B:E OL B:C 1.134
Q4 B:E 0.323 B:C 0.591 / reversed leads B:E 0.396 B:C 1.022

Continuity between E:C, checked out, no shorts on all 4 BC transistors

Measurements made w/ M2 installed, M1 is out of circuit at the moment.

LED's tested correctly.

Thanks again,

Jim

 

[Salas]

LEDS check, OK.
Those are all NPN transistors. The red probe was always on B pin (as it should) when you measured the junctions against C, E, pins?

 

[Salas]

Video help

 

[JKiriakis]

Correct, the figures above on the left side, red probe was always used on B base when measured against C collector and E emitter.

 

[Salas]

I would replace Q1 & Q2 first

 

[JKiriakis]

Re-measured post video, changed to Extech DMM:

Q1 B:E .020, B:C .541
Q2 B:E .096, B:C .578
Q3 B:E .580 B:C .610
Q4 B:E .543 B:C .122

Double checked I got it right. What say you as to what to replace?

 

[Salas]

Q1 Q2 suspicious

 

[JKiriakis]

I changed out Q1 and Q2. Re-powered briefly. No light from LEDs and R1 immediately hot with a wisp of smoke, same fault as prior.

 

[Salas]

Bummer!
See if the print on M1 M2 reads the right types at right places for negative Ubib

 

[JKiriakis]

Thank you, Salas. I took at close look relative to the schematic per your advice. The offending negative rail M1 = FQP 3P20. Schematic calls for FQP 3N30.
M2 has IRF530. Schematic calls for IRF9530

On my 5VDC working UB, M1 if FQP 3N30. M2 neg rail has IRF9530. And the other TB supply kits on the neg side have those, too.

Could this be the cause of the fault?

 

[Salas]

Much so