Simplistic MosFET HV Shunt Regs

[merlin el mago]

DMM set to Hz reads 0Hz at the real load, before the PSU reads 50Hz

 

[Salas]

So it does not read your small mV hum at the output, reads random things there, but it reads some higher level hum that is probably coming into the PSU. The PSU CCS rejects most but some rather remains in the ground side.

 

[merlin el mago]

The SSHV is set to 30mA but can't go more than max Vout 83V, the mains transformer is 240VAC 118mA.

 

[Salas]

Needs more CCS setting for that specific load? Or its voltage setting side has some problem?

 

[merlin el mago]

Attached schematic used.

 

[merlin el mago]

The load needs 20mA, 10mA for each triode.

 

[merlin el mago]

When set to 30mA the voltage setting can't go higher that 83V

 

[merlin el mago]

The B+ voltage is set with the -3.3V grid bias?

 

[Salas]

The load needs 20mA, 10mA for each triode.

10+10=20mA. +20mA we usually recommend for SSHVs own=40 mA CCS is better. + more mA if the triodes will swing high.

 

[Salas]

Attached schematic used.

See that the anode transformer's shell is also grounded not to pick interference.

 

[merlin el mago]

I set the CCS to 40mA and come back with result.

 

[merlin el mago]

Can't change Vout is fixed to 92,5V

 

[merlin el mago]

See that the anode transformer's shell is also grounded not to pick interference.

Attached transformer pic, do you want that I connect the transformer to signal ground?

 

[Salas]

But it went up from 83V so see if it can really work on 20mA needing dummy load at target B+ first. If not, something must be broken in the voltage setting section.

 

[Salas]

Attached transformer pic, do you want that I connect the transformer to signal ground?

If the chassis is already referenced to signal ground, no, if not, yes.

 

[merlin el mago]

The chassis only have mains earth and a separate SLB

 

[merlin el mago]

The last PSU cap is connected to SLB and after to the chassis not shared with mains earth.

The 2.2uF film cap of heaters regulator is connected to signal ground and to SLB, this can be cause the ground loop?

 

[merlin el mago]

The B+ voltage is set with the -3.3V grid bias?

?

 

[RollE2k]

Why not use LED bias on the cathode instead?
I haven't used battery bias, but isn't it supposed to be between the grid and ground, with a input cap before the battery...?

 

[merlin el mago]

SSHV2 works OK with dummy load and can change the Vout.

Now I used 6K8 10W dummy load set the voltage to 136V to burn 20mA so after I will connect the real load to see what's happen with B+

I will keep you informed.