El Cheapo Circlotron PSU question....

[Alastair E]

Ive bread-boarded a circlotron using 2x 6c33c in O/P stage, diff amp feedback round O/P stages and Mu pre/voltage amp.

As the available mains toroid Tx is a 650 va 0-55, 0-55, I use a voltage doubler to get the two main circlotron supplies around 160V using nice large caps, of 6.600uF, at 200V

Im using a smaller standard iron for the pre-amps HT and bias supplies etc as well as the other heaters.

It would be a nice easy set-up, (Read, Cheap and cheerful!) to use one AC 55v side of the toroid, and add a small winding to drop the AC to 50V (wired in antiphase to the 55V) to supply the heaters of 4 x 6C33C series wired, and the other 55v winding similarly arranged to supply the heaters of the other channel. (I plan to use 4 O/P tubes rather than two per channel in the completed amp....)

The Max heater to cathode volts of the 6C33c is around 300V

Doing this, I can get rid of the current heater transformer which just supplies the 6C33C valves, and its not up to running 8 valves.....

I know a voltage doubler is far from ideal for the circlotron rail supplies, but Im using just what I have around at the moment, I can upgrade later--Currently running just one channel it seems quite good, and I have more big caps which I plan to use in the next revision......

Is there any issue Ive overlooked, like heater current hogging by one or two valves or something really silly Ive completely missed?

Thanks!

[richwalters]

Somehow we need a scribble (or whatever diagram ) to double-check whats' actually going on. I use doubler itechnology in my amps....I'm for it.... as it cuts down winding resistance, so long it can handle current rating.

richj

[Alastair E]

Originally posted by richwalters
Somehow we need a scribble (or whatever diagram ) to double-check whats' actually going on. I use doubler itechnology in my amps....I'm for it.... as it cuts down winding resistance, so long it can handle current rating.

richj

Im sorry, I dont actually have a diagram on the PC. Basically, the circlotron uses two floating 160V supplies. These have no direct connection to ground and are allowed to 'float' (although they are referenced to ground on their neg rails, by a 330 ohm resistor--Each supply has its own resistor to deck, so between the two neg rails, there is 660 ohm, the centre of which is grounded...The output signal is derived between the neg rails.)

the supplies are derived by the two voltage doublers from the two separate 55V windings from the Toroid. There is no other connection to the 55VAC or the doublers

I was interested in using the same 55VAC windings to also supply the heaters of the 4x 6C33, series wired, one winding to supply one set of four valves, the other to supply the second set of 4?