813 power supply question

[Richard Ellis]

Ok, here it is my revised 813 triode strapped SE supply.
This is one of many supplies I will need on this project......I just need someone to crunch the math....sin & cosine seem to have evaded me as I haven't used it since long ago........& I can't seem to remember how to punch up the numbers. I have 'Morgans' book & can to all the math EXCEPT this one....looking for the ripple figures. The load this supply will "see" is 90 milliamps per tube, I guess I will need two of these supplies.
Or do I ???
_______________________________________Rick..........

 

[soundbrigade]

Two?? One for each channel?

Have a run with Duncamps PSU Designer: PSUD II .

 

[TonyTecson]

Ok, here it is my revised 813 triode strapped SE supply.
This is one of many supplies I will need on this project......I just need someone to crunch the math....sin & cosine seem to have evaded me as I haven't used it since long ago........& I can't seem to remember how to punch up the numbers. I have 'Morgans' book & can to all the math EXCEPT this one....looking for the ripple figures. The load this supply will "see" is 90 milliamps per tube, I guess I will need two of these supplies.
Or do I ???
_______________________________________Rick..........

hi,

your input to the bridge is way too high, 2000volts will give you a rectified unloaded 2800 volts dc....

if you use just one half of the secondary it will give you 1400 which is more managable.....but still high....

looks like your transformer is good for one tube, what is the va rating?

😀

 

[Richard Ellis]

Tony, The spec on the Transformer is one thousand peak RMS!. As you'll recall Peak is 1.41 up on RMS.
So it all translates to nine-hundred or so at the output.

 

[TonyTecson]

Tony, The spec on the Transformer is one thousand peak RMS!. As you'll recall Peak is 1.41 up on RMS.
So it all translates to nine-hundred or so at the output.

yes, but your schematic as shown has the 1000-0-1000 inputted to the bridge, perhaps you are thinking of full wave centertapped config...in which case you need just 2 diodes and the center tap connected to the minus leg..

 

[7N7]

Yes it's a choke input supply so output voltage is 0.9 and ouput current is x 1.414. Therefore it should be two diodes and centre-tapped as already mentioned.

The operating point you have chosen is pretty good based on my 813 experiences. Actually you should run them at about 900V and 100mA, (4k for SE, 8k for p-p) this was my target when I was messing about with 813

7N7

 

[Richard Ellis]

OK...I'll concede to the two diodes. The iron is rated at 150 mA at Continuous Commercial Service or CCS. The other rating is 225 mA for Intermittany Commercial or Amauter Service or ICAS.
The upshot is that at a 90 mA draw one TX is fine, but driving both tubes will be a stretch treading on intermittant use/
Has anyone run into this problem of Commercial vs. Amauter ratings?
_______________________________________Rick............