Power supply help

[lochness]

So this is my first "complicated" power supply I'm making and I don't know where to start. Its for a mono version of this amp.

It needs to be able to supply 410V and about 125ma (I'm simply halving what the transformer he used in his schematic, a hammond 372JX, could provide in ma). Its a bit of over kill but I want to use my 4B32's to rectify the supply (half wave each and have about a 12v voltage drop, 16v MAX. Page on them. ). I want to go with a simple LC filter as I have had problems in the past with capacitor input when using gas rectifiers.

The part I really need help with is making it a tube regulated supply. I don't have the foggiest idea of where to begin (though I know I want to somehow fit a 6C33C in the design for the irony). If it makes any difference I plan of having the transformers custom made. This amp is for a sub woofer as well.

[lochness]

Sorry for the double post but I saw no option for editing my previous post.
To get the basic layout of the power supply I decided to use a program (PSUD2) instead of doing all of the math out by hand (mainly because I lost the formulas my friend gave me and I didn't feel like deriving my own). I'm not 100% sure I'm using it right (I had never considered the resistance of the mains transformer windings and the filter capacitor). I also couldn't find a model for the 4C32 so I used one for the 3B28 (next best thing as far as I know).
As far as I can tell from the program a 245-0-245 transformer (490VCT) into a hammond choke (10H, 82ohm) with a good valued capacitor will give me ~410v depending on the load (was assuming the primary impedance of the output transformer a good value for Rload? I've never designed a power supply this way. I've always been a "trial-error-eh?-meh...good enough" kind of guy).

Is this a good starting point or did I screw something up in the program?

[Eva]

If you really want to experience new things, how about an off-line flyback? It's far more efficient in every respect (stray fields/EMI, cost, size, weight, output regulation, current limiting, losses, life expectancy...) And you only need 50W...

[lochness]

If you really want to experience new things, how about an off-line flyback? It's far more efficient in every respect (stray fields/EMI, cost, size, weight, output regulation, current limiting, losses, life expectancy...) And you only need 50W...

Hell no! I've seen fist hand what flyback transformers can do...joe still twitches every once and a while. I stay away from those things...

[Eva]

That was not worse than the harm that 490V AC or a 10H choke charged to 100mA can do

I have no experience with tubes, but if this class A choke loaded output stage is properly biased, it should be conducting slightly more than 410V/4800ohm~=90mA when idle (I suppose the pots are intended for bias adjustment). Current consumption may double during negative signal peaks and may drop to 0 during positive peaks, so net current draw remains at 90mA.

BTW: A good 400V flyback SMPS would actually have four 100V outputs in series to allow to use 200V ultrafast diodes. This has nothing to do with the 25KV to 50KV secondaries found on TV flybacks...

[lochness]

Yup I think that is what the pots are for. Really never played with choke loaded tubes seriously but it's suppose to be better.

Is what I've worked out for the power supply correct so far?
How do I regulate it with tubes?

[wakibaki]

Here's a thread with some interesting stuff on HV regulators, although the regulators discussed are transistor types.

High Voltage Regulator

Can you post a schematic? And a description of your assumptions or datasheet parameters?

490vrms is ~680 pk, so 410V sounds a little low

What regulated output do you require?

w

[wakibaki]

I'm not really a tube guy, but this is what I think a tube regulator might look like.



w

[lochness]

This is what I've been playing with but I don't know what certain values should be. Any help would be appreciated.

[wakibaki]

OK, like I said, I don't really do tubes, I did them in school years ago, but it's been silicon ever since...

I had a play with PSUD2 and I looked at your circuit. From first principles the topology you have chosen will produce a peak output of <346V with 245v secondaries (rms volts * sqrt(2)). Therefore the value you should enter in the transformer properties is 245 not 490.

Entering the values for the choke and cap as in your circuit gives me an output voltage of ~200V with a 5k load. 5k is not an unreasonable figure, but you can backfigure the load by dividing your target voltage by the anticipated current draw 410/0.125 =3280ohms. V=IR.

Messing with the capacitor resistance value (ESR) affects mostly the ripple, so this is a parameter with a minor influence on your output voltage. I'm a bit surprised that so much voltage is lost as a result of the tx resistance and choke, but you live and learn.

To get the voltage you want with the 2-tube fullwave rectifier you will require a much higher voltage secondary, about twice what you have now.

Maybe somebody who's a bit more up to speed on this will chip in.

w