The simplistic Salas low voltage shunt regulator

merlin el mago · 2010-03-06 4:16 pm

ikoflexer said:
Yes. More importantly though, you should measure between 5 and 6 volts across the LEDs.

My advice is to implement the exact schematic (using bc546) that I showed above, and if you measures very close to the values indicated on the schematic, then you have the CCS, a current limiter, working well. Only then move to the next section, the shunt part, without fear. Because no matter what happens in the shunt portion, your current limiter will not allow anything to happen in case of a short circuit in the shunt.

With battery as the pic posted measure 5,61V across the LEDs.

R1 & R2 can be 0,25W?

This schematic is for use with the PS or with battery, I suppose is for running with the PS, right?

klewis · 2010-03-06 4:16 pm

Salas said:
That one will run +/-180mA if your Leds can reach 2V Vf for about 2.5mA. Else, about 150mA. R1 sets that. ICCS=(Vf3LEDStot-Vgs)/R1. Fix it given your actual parts. The trimmer gives you an adjustable Vout. Don't ask more than 65V out. You can use BF245A if you can't get 2N5457, don't use anything more than 3mA IDSS collector load, so to keep the error amp BC546B dissipating conservatively. Remote sensing is recommended. You have seen how on the one I showed for Merlin a few pages back. Good luck.

Salas,

Other than adjustablity, is there an advantage of using resistors at R6 vs a zener? Fairchild has 1nxxx zeners in higher voltages.

Ken L

Salas · 2010-03-06 4:20 pm

Merlin, that photo without words, verifies that +V battery at Vin+ lights them up so they are correctly oriented? May we :checked:

?

Salas · 2010-03-06 4:21 pm

klewis said:
Salas,

Other than adjustablity, is there an advantage of using resistors at R6 vs a zener? Fairchild has 1nxxx zeners in higher voltages.

Ken L

Less noise potentially depending on the particular Zener part quality in comparison.

merlin el mago · 2010-03-06 4:32 pm

Salas said:
Merlin, that photo without words, verifies that +V battery at Vin+ lights them up so they are correctly oriented? May we ?

Ok I post the pic to show you. I do as the Jig to match the LEDs: 1Kohms in series between the battery + & the LEDs to be matched.

merlin el mago · 2010-03-06 5:54 pm

merlin el mago said:
With battery as the pic posted measure 5,61V across the LEDs.

R1 & R2 can be 0,25W?

This schematic is for use with the PS or with battery, I suppose is for running with the PS, right?

Please Iko let me know?

miguel0f · 2010-03-06 5:56 pm

Hello all,

I want to build a +/- 15V power supply for a phono pre-amp stage, and after looking around about the different projects in the forum, I'm inclined to build the circuit you're discussing here.

The intend to install the power supply (including transformer and rectification) in the same box as the pre-amp, which by the way, is the balanced outpur version of the RIAA phono pre-amp stage from Douglas Self.

As a starting point I would like if anyone could please indicate me which version (post?) of the circuit should I start looking at?

Thanks in advance,

iko · 2010-03-06 6:03 pm

Sorry, I missed that question. Yes, R1 and R2 would work if 1/4W. Yes, the schematic would be for PS, not battery. I'm going to go out run some errands soon, so if you have results soon I might be able to comment, otherwise, later. Good luck!

Salas · 2010-03-06 6:07 pm

miguel0f said:
Hello all,

I want to build a +/- 15V power supply for a phono pre-amp stage, and after looking around about the different projects in the forum, I'm inclined to build the circuit you're discussing here.

The intend to install the power supply (including transformer and rectification) in the same box as the pre-amp, which by the way, is the balanced outpur version of the RIAA phono pre-amp stage from Douglas Self.

As a starting point I would like if anyone could please indicate me which version (post?) of the circuit should I start looking at?

Thanks in advance,

Page #190. V1.2 Symmetric. Only an R-Core can be installed totally quietly in a single Riaa box is my experience.

merlin el mago · 2010-03-06 7:01 pm

Hurra, the LEDs are lit

the problem was that I forgot the connection between LED's/R2 & C1/Q6

Now I have 55V after the reg. but I need 45V & the trimmer pot only increase or decrease 0,2V?

RCruz · 2010-03-06 7:25 pm

Can you measure vdrop on R3 under the vref jfet ?

Salas · 2010-03-06 7:39 pm

Merlin: Focus on all remaining connections, see detail. Q5's Drain connects up to the 4k7 & 47 node. Trace your work carefully.
La Ode already runs a second circuit like yours in symmetric, this time integrated in his Pass D1 DAC analogue section. Hurry up, we got to compete with Asian productivity, else in IMF we ClubMed soon.

RCruz · 2010-03-06 11:31 pm

Cool

Salas · 2010-03-06 11:35 pm

With so big heatsinks surely stays cool.

merlin el mago · 2010-03-06 11:56 pm

RCruz said:
Can you measure vdrop on R3 under the vref jfet ?

Voltage across R3 is 0,06V

Salas · 2010-03-07 12:03 am

That is 6mA on a 10R. Your Jfet CCS works. Your trimmer + resistor seems at full. By turning it off power and measuring across V+ Out and 47R/Jfet node see if your resistance changes when you turn the trimmer. If not, review your connections on it. You will need 7.4k total for 45V.

merlin el mago · 2010-03-07 12:45 am

Now the reg. give a nice 45V, BRAVO I am the happiest man in the world, for all the people will see easy but for me is a big step. The mistake was not connected properly Q4 with C4 & a bad GND connection.

Tomorrow will connect the NJFET RIAA.

Many thanks to everybody & good night.