Salas SSLV1.3 UltraBiB shunt regulator

[stew1234]

Are there any technical advantages to using IRF9610 and IRF610 at M1 over FQP3P20 and FQP3N30 for <1A of cc? If I have access to both is one choice better than the other for about 200mA and 300mA of cc?

 

[Salas]

Small differences in parasitic pF more in Vgs(off) keep the FQPs for higher amperage apps as the 9610/610 are more ubiquitous and maybe bit faster.

 

[Malefoda]

Useful to have boards to build when you need to take your mind off things.
Thanks Salas and Tea-Bag for these great projects!

L-Adapter up and running (a music server), UltraBiB in progress.

 

[stew1234]

Salas, I just powered up a positive ultrabib for the first time. I cannot adjust vout with VR1 - it is measuring 4.91vout. M1 is warm but M2 is not giving off any heat. Both LEDs are illuminated. Any suggestions?

 

[Salas]

After rechecking all semis are the right ones at the right places see if Q2 Q3 actually give 0.61V Vbe and M2 few volts Vgs. Also retouch Q2 Q3 C2 joints.

 

[Salas]

Useful to have boards to build when you need to take your mind off things.
Thanks Salas and Tea-Bag for these great projects!

L-Adapter up and running (a music server), UltraBiB in progress.

You are welcome. Nice photo by the way.

 

[stew1234]

Confirmed all semiconductors are in the correct place and I re-flowed Q2, Q3 and C2. Still no change.

M2 measures 3.58v (between two outside pins)

Q2 and Q3 measure .625v (middle and right pin when facing the flat "face")

After rechecking all semis are the right ones at the right places see if Q2 Q3 actually give 0.61V Vbe and M2 few volts Vgs. Also retouch Q2 Q3 C2 joints.

 

[Salas]

Does the trimmer change Ohmic value between its outer pins when turned?

 

[stew1234]

It's a bit tough to measure now that it's soldered, but at one extreme I'm measuring approx. 75ohms and when turned the other way it reads about .4. When I turn back 5 or so turns I'm reading 72.5. I used these 10k variable resistors.

3296Y-1-103LF Bourns | Mouser

 

[Salas]

But you only got 4.91V output that doesn't change at all with the trimmer right? What transformer you use? What is your target Vout? How many mA CCS you can calculate by drop on R1 divided by its Ohms? Is the output free or loaded with something?

 

[stew1234]

Correct, vout doesn't change. I'm using a 50va 2x15v toroid. I get 15vout on the other secondary with a different power supply. My target vout for the ultrabib is 15v and 200mA CCA. Right now I have a 3ohm resistor at r1. The 4.91v is unloaded, when I use a 20ohm resistor I have as a load, this drops about 1v to 3.9v.

 

[Salas]

When there is ~0.6V as to be expected across R1 you have CCS of 0.6V/3Ω=200mA. Loading 4.91V/20Ω=245mA. So the drop to 3.9V is correct due to current limiting.

 

[Salas]

When all bias voltages seem proper could it be your vrr is a 75Ω resistor instead of 75k by mistake?

 

[stew1234]

After double checking, yes you are correct! Thanks.

When all bias voltages seem proper could it be your vrr is a 75Ω resistor instead of 75k by mistake?

 

[Salas]

For your 15V target with 10k trimmer you may even leave vrr out if a 75k isn't handy to replace.

 

[altsouza]

Hi @Salas
Just another newbie question.
I have a 15+- ultrabib I am not using.
The positive board I am using for a Dac.
Is it possible to transform the negative board into a positive one.
I have a empty positive pcb.
Thanks
Antonio

 

[Salas]

Antonio hi

If flipping the bridge diodes & LEDS and the capacitors when replacing with opposite type BJTs and MOSFETs while the particular JFETs are supposed to be electrically symmetrical, its theoretically possible to succeed although I haven't tried it.

 

[altsouza]

Thanks

 

[jimk04]

I see the +/- boards are electrically seperate. I have 2 18v toroids from when I built DCG3 with DCSTB. I purchased these wrong for thr DCSTB.....these trafo have just 1 output(2 wires). So would these 2 trafo be ok to power Ubib.....seperate trafo for each rail....aiming for 15v so maybe a little 'hot' secondaries?

 

[Salas]

Yes you can use them