Simplistic Mosfet HV Shunt Regs

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If you shorted S0-F0 and NOT shorted S+ - F+, the regulator part and shunt FET not working.
In this case CCS can be tested with low DC voltage.
Use 10-12V input voltage and measure CCS current via F0-F+ with current meter.

12V*0.065A= 0.78W so CCS with even small heatsink can be tested.

If CCS working well (for example 65mA, as above), try to test with dummy load: 4k7 10-25W.

Sample:

SSHV2 220V DC dummy test.jpg
 
If you shorted S0-F0 and NOT shorted S+ - F+, the regulator part and shunt FET not working.
In this case CCS can be tested with low DC voltage.
Use 10-12V input voltage and measure CCS current via F0-F+ with current meter.

12V*0.065A= 0.78W so CCS with even small heatsink can be tested.

If CCS working well (for example 65mA, as above), try to test with dummy load: 4k7 10-25W.

Sample:

View attachment 1132695

CCS is working ok: with trimmer got near 100mA, tomorrow I will try the 4K7 10W as dummy load.
 
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Felipe,

If the CCS is working (#6663) and the all SSHV2 working too (#6664) what's the problem?

Set CCS to 41mA (the shunt current will be about 12.2mA, the other parts currents 3.8mA, so the regulator part current 16mA).
Set input voltage of SSHV2 to 280V.
Try dummy load for -about- 25mA: 220V/0.025A=8k8
Set SSHV2 pot until output is to 220V.

If the valve real current is 25mA, the output voltage of SSHV2 will be around 220V. Correct it with potentiometer.
 
I don't know what's the problem Bela, but to have 45mA CCS I have to reduce SSHV2 to 269 Vout & Valve Itch needs 300V & 45 mA!!!!

If Vout is more than 269V the CCS stars to reduce it, if I set 300 Vout the CCS is 22mA only.

Of course the CCS trimmer is set to max. mA

Now CCS is working with two cascoded DN2540 as per Salas design.
 
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Insufficient HV raw supply.

I asked you in #6655:

"Is HV raw supply (especially PT secondary) has enough current capacity?
Did you test it with dummy load?"

You wrote:
"PT 250VAC 0.2A.
No.
I guess yes, target B+ is 300V."


With tube rectifier (even in hybrid layout and CLC smoothing) it will never produce 300V DC SSHV2 output at 45mA load.
Requiring raw voltage = 300V + 30V CCS headroom aka. 330V at SSHV2 input.

You measured it perfectly:
"I can't set the SSHV2 CCS to 45mA only max. 22mA with a load of 300V."
250V AC testing.jpg

It's the physic.


-----------------------------
First of all, test PT as attached pics shows.
250V AC testing.jpg


If it only 250V AC with load, it's the bottleneck.
----------------------------
BTW "Valve itch phono" current requirement is 25mA????
In the schematic 1mA+6mA= 7mA per side, so overall requirement only 14mA.

If it's true, the SSHV2 CCS current settings to 25mA is perfect.
 
Last edited:
Insufficient HV raw supply.

I asked you in #6655:

"Is HV raw supply (especially PT secondary) has enough current capacity?
Did you test it with dummy load?"

You wrote:
"PT 250VAC 0.2A.
No.
I guess yes, target B+ is 300V."


With tube rectifier (even in hybrid layout and CLC smoothing) it will never produce 300V DC SSHV2 output at 45mA load.
Requiring raw voltage = 300V + 30V CCS headroom aka. 330V at SSHV2 input.

You measured it perfectly:
"I can't set the SSHV2 CCS to 45mA only max. 22mA with a load of 300V."

First of all, test PT as attached pics shows.
View attachment 1133046


----------------------------
BTW "Valve itch phono" current requirement is 25mA????
In the schematic 1mA+6mA= 7mA per side, so overall requirement only 14mA.

If it's true, the SSHV2 CCS current settings to 25mA is perfect.
Bela mine PSU it's very similar CRC 0,47uF-1R-820uF without choke
 
Surely Salas told me to set the SSHV2 to 45mA, mine Valve Itch uses other valves and the schematic is a little bit modified. Attached schematic, if I remember correctly the 7N7 runs at circa 9mA each so 9 x 2 = 18mA + 2mA each E283CC total 20mA + 20mA SSHV2 self consum = 40mA near Salas advice.
 

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  • Valve Itch Rev 1.2 FELIPE 7N7 (2019_07_02 11_22_03 UTC).png
    Valve Itch Rev 1.2 FELIPE 7N7 (2019_07_02 11_22_03 UTC).png
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