Simplistic mosFET HV Shunt Regs

[merlin el mago]

OK thank you.

Salas SSHV2 must be chassis grounded at C1 leg?

 

[Salas]

That's symbolic in the schematic. If you have to, better at the reservoir capacitor's zero. But the application must NOT require floating B+

 

[merlin el mago]

Salas measuring the B+ SSHV2 gone due to a short between B+ & GND. 2SK117GR 4-5mA is gone I have a couple of alternatives because I don't have more 2SK117GR 4-5mA:

SK117BL
3.04 or 3.41 or 3.50

SK117GR
lowest value 4.60

Wich one?

 

[Salas]

BL ~3-3.50 rather fake, BL must be 6-14mA says Toshiba

Try the GR (2.6-6.5mA legit)

 

[merlin el mago]

So could I use any GR between 2.6-6.5mA?

Attached damaged, is gone, right?

 

[Salas]

Gone forever

 

[Salas]

If the Vout is not too high low GR can be used also and reach

 

[merlin el mago]

Vout is near 100VDC because is at the plate but before is an OPT.

What's the max difference Vin vs Vout SSHV2 can handle?

 

[Salas]

As much max VDS and max dissipation the D-MOS on your sink can

 

[merlin el mago]

OK I will keep the 20V of difference.

Q5, Q6 & D3 gone.

Issue fixed, thanks Salas.

 

[Salas]

You also solved the AC readings issue after repairing the damage by the accidental short?

 

[merlin el mago]

Yes Salas.

 

[widi]

sshv 2

Hello, Mr. Salas,
Some time ago I built my stage phono which I am very happy, but I have a buzz (photo of the oscilloscope at the end of the phono stage) around 75hz I use the sshv2, which works well for me or that, I adjust both tension and the current, the operating voltage is dl phono stage is 255 volts and the current is adjusted to 35ma. Attached photos of the phomo stage and psu.
Could it be a malfunction of sshv2 that produces such noise?

 

[Salas]

Hello

Was it there before or it recently appeared? Can you also find it when probing the rail? Use AC scope coupling, 1:10 probe setting and short wire ground probe tip accessory for that. It can be intereference or ground loop. Although 75Hz is a weird frequency to be hum loop.

 

[widi]

sshv 2

Thanks for answering, the noise was already in the first moment that I started the phono stage.
When reviewing the ssvh 2 output with the oscilloscope I can not see anything alarmingly, attached screenshots

 

[Salas]

It's not coming from the PSU even when you use a long ground for the probe which can pick intereference like an antenna.

So, look for wide loop areas to be narrowed in the signal and it's return wiring or for some shielding issue, including tubes shielding.

 

[widi]

sshv 2

Thank you very much Mr. Salas for your help.
I will review all the wiring again, but I have a doubt when you refer to the shielding of the tubes, can you explain it to me?
Thanks again

 

[Salas]

Shield caps that lock to proper bases. It takes rework to fit new bases though. So see about magnetic fields from nearby transformers first. Even those in other boxes but in vicinity.

 

[Salas]

Still look again on the rails with short ground tip and more sensitivity in AC coupling scope mode. I am on mobile now and I don't see the screen shots in detail. So make sure.

 

[widi]

sshv 2

Still look again on the rails with short ground tip and more sensitivity in AC coupling scope mode. I am on mobile now and I don't see the screen shots in detail. So make sure.

Thank you Mr. Salas, I will review everything again and take your advice.
I put the oscilloscope back to maximum sensibility and attached screenshot,
For me, it is correct