Simplistic Mosfet HV Shunt Regs

[king4joy]

OK...ok....I will use 25W...or 50W....thankyou....

[Salas]

You are welcome. I still remind that using the simulator I linked and giving it the chokes resistance and other parameters correct, you may have a good estimation.

[king4joy]

I have downloaded the PSUDII...thanks.....but I need to take time to learn....and I do not know the resistance for the caps.....

[Salas]

Don't worry about cap's ESR, very small and in parallel. Especially if they are film caps put something symbolic like 0.001 Ohm and forget.

[commstech]

if i were to build the PSU in separate chassis from my preamp, will having the SSHV in the PSU chassis with about 1m of wire running the regulated B+ to the preamp chassis affect the performance? what is a logical distance of wire after the SSHV output that will not discount too much of the intended performance? anyone experimented and measured?

[roger57]

Tea Bag / Salas

I'm hoping to use a light-pipe off the top of the ref LED in the SSHV2 to get a panel indicator. However, the brightness of that LED is rather low. I measured the voltage across R10, and calculated the current to be about 1.9mA.
I took a spare LED (bought 2 kits) and put it in an LED tester at the 2mA setting, and it's quite a bit brighter. Not sure why this is? If Salas is reading these posts, he may have a comment on this (I hope) with regards to a slightly brighter substitute that wouldn't upset the balance of the reference circuit?

My question to you Mike is what's the DK or Mouser part number of that LED? I'm going to try to find a replacement with the same specs and hopefully a tighter viewing angle that will give me more forward light.

Regards,
Gary

[Salas]

Originally Posted by commstech

if i were to build the PSU in separate chassis from my preamp, will having the SSHV in the PSU chassis with about 1m of wire running the regulated B+ to the preamp chassis affect the performance? what is a logical distance of wire after the SSHV output that will not discount too much of the intended performance? anyone experimented and measured?

I have had 1.5m long 4 wire tightly twisted pairs working stable.

[Salas]

Originally Posted by roger57

Tea Bag / Salas

I'm hoping to use a light-pipe off the top of the ref LED in the SSHV2 to get a panel indicator. However, the brightness of that LED is rather low. I measured the voltage across R10, and calculated the current to be about 1.9mA.
I took a spare LED (bought 2 kits) and put it in an LED tester at the 2mA setting, and it's quite a bit brighter. Not sure why this is? If Salas is reading these posts, he may have a comment on this (I hope) with regards to a slightly brighter substitute that wouldn't upset the balance of the reference circuit?

My question to you Mike is what's the DK or Mouser part number of that LED? I'm going to try to find a replacement with the same specs and hopefully a tighter viewing angle that will give me more forward light.

Regards,
Gary

That LED is not there primarily for indication but for Tempco. Check your F+S+ (B+) output rail on the scope that is oscillation free so the dimness isn't a product of interference. If everything is OK I still recommend you wire another dedicated panel LED of your liking from input side. If you got say 300V input then a 100K resistor would allow ~3mA to a 2V LED and it will double as a discharge bleeder for the rectification filter capacitors to discharge. By the time the LED is out you know there is minimal stored energy, not just the reg had stopped. Its good for safety.

Led current in the above example=(available voltage-Vf)/R. Use nominal power resistor of 2 to 3 times more than led current times voltage source.

[roger57]

Originally Posted by Salas

That LED is not there primarily for indication but for Tempco. Check your F+S+ (B+) output rail on the scope that is oscillation free so the dimness isn't a product of interference. If everything is OK I still recommend you wire another dedicated panel LED of your liking from input side. If you got say 300V input then a 100K resistor would allow ~3mA to a 2V LED and it will double as a discharge bleeder for the rectification filter capacitors to discharge. By the time the LED is out you know there is minimal stored energy, not just the reg had stopped. Its good for safety.

Led current in the above example=(available voltage-Vf)/R. Use nominal power resistor of 2 to 3 times more than led current times voltage source.

Hi Salas,

Since I already have a bleed-down resistor in the DC "bulk supply" to the SSHV, that's won't be a problem. I realized I could have done this, but running a bit tight on supply current. I guess it will come out of the shunt side, but will still be pretty good (about 80% overhead)

I had the light pipes already so I thought it would be a good opportunity to use them and not use any more current.

As for the LED brightness, I'll follow up and scope the output for noise. Had not seen any before but that may have changed since a few months.

Thanks!
Gary

[merlin el mago]

I'm usings SSHV2 with hybrid rectifiers: 2 UF4997 + one tube AZ1, whit 15K dummy load all is OK can set B+ to +280V but when I connect the Mu-Follower the AZ1 shines a lot, the red led of the SSHV2 don't lit, I have the reg set to 32mA, the mu-follower draws 3mA per channel, please help?