Bench PSU

[sorenj07]

here's a schematic I drew up for a pretty simple bench supply. I think it was Tubelab that gave me the idea, of feeding a huge control transformer with a variac. I have everything but the variac and the diodes (figured 5A 2KV but they could probably be 2A). What do you think? Should I tack on some SS regulation? more capacitance?

An externally hosted image should be here but it was not working when we last tested it.

EDIT: I realize now that the tap on the variac should be on the other side, otherwise it steps up the voltage...

 

[Tubelab_com]

I have since added a big choke that I got surplus (specs unknown) and another set of caps to make a CLC filter.

Add fuses to the input to keep the fireworks to a minimum when the circuit under test decides to short out.

 

[sorenj07]

I don't have oodles of cash at the moment, but what type of choke would you recommend to use? I'm currently looking at a Hammond 193Q, 10H, 500mA, 53 ohms. It'd limit the total current output but half an amp is still pretty significant, certainly more than I could conceive of needing at any one time.

As I start fooling around with a 6S19P amp I'm drawing up I'll want a nice variable B+ supply, and this looks like it could be a pretty economical solution.

 

[Tubelab_com]

I found a choke at a surplus shop for $5. I have no idea what the specs are, but it weighs about 10 pounds and the wire size looked about right. I am of the opinion that any choke is better than no choke. I use these in my budget amplifiers:

http://www.alliedelec.com/catalog/pf.asp?FN=927.pdf

Look at the bottom of the page, ugly but cheap. I use C-14X and C-24X in my tube amps. These would impose a bigger current limitation, so You may want to use the Hammond choke.

 

[sorenj07]

The Hammond is probably the way to go. I already have a 193M I think (10H 300mA ~63R) that I might use, but I'll definitely want something more substantial in the future.

 

[Tweeker]

If you need more current than 193Q theres Hammond 159Y 0.6H, 750ma, 11 ohms. Can be had for $22. Beyond this you may be straining the PT and variac, especially given the 250uF input capacitor. Whichever choke you use, follow it with an oil motor run cap if possible. Midori Meadows has been selling nice 80uF 500VAC motor run caps for $12.