Cap size for Hg Rectifiers

[Steven-H]

All,
I have tried to look at some data sheets in the last couple of days, but I haven't been able to find this answer....
What is the acceptable input cap value for Mercury Vapor rectifiers (Namely interested in the 83/816) to make it live a happy life ?

Thanks !
Steve

[bembel]

hi,
IIRC it's less than 40µF with an input choke > 3H (for a 83)

hope this helps.

[EC8010]

Zero. Hg rectifiers are intended for choke input because of their negative output resistance.

[bembel]

Oops I was meaning 40µF after the >3H input choke.
sorry & thanks EC8010

[EC8010]

No apology necessary - I can't make myself as clearly understood in French as you can in English.

[bembel]

those are explosive mistakes !

[Steven-H]

Thanks Gents....This leads me to another question.

In looking here:
http://www.diytube.com/st35/ST35_5AR4PS.pdf

One can see the PSU arrangement. I will be subbing in an 83 tube, so by taking your recommendations I will be ditching C9, and increasing the choke to 5H or so. Any other changes ? I already have a timer delay circuit in place, so the preheating issues are taken care of.

Secondly, the main cause for me asking this question is I wish to use a set of 816s in my PSU that will power my preamp/phonostage. I've been playing around with PSUd for a while, but I haven't been able to come up with anything too impressive. I guess I have a couple of issues; first one being that I am using an 83 tube to design the circuit; as PSUd doesn't have the 816 (But I believe it would be pretty close...). Secondly, I was planning on using a set of 0D3 regulator tubes; of which PSUd doesn't have as well. Do any of you have some tried and true suggestions ?

Thanks again,
Steve

[sorenj07]

Taking out the input cap from the power supply will drop your voltage by a LOT. instead of multiplying the transformer's AC voltage by root 2, you decrease it by 10%. Unless you have a much higher voltage power transformer than the one DIYTube specifies, you won't be able to use this schematic.

[Steven-H]

Thanks.......So I suppose my option is now to either use a 450v or so transformer; or a 'normal' rectifier tube....

[rdf]

Most spec sheets for the 83 mention operation with a capacitor input, typically with a min recommendation of 50 ohms total source impedance in series with each plate when using a 4 uF input cap. Why the big fat 'zero'?