Heathkit condeser checker power supply

[maxkracht]

I was given some old heathkit gear and have been thinking of ways to repurpose some of it. The last owner pulled all the tubes he found useful and I don't find any of the pieces interesting enough to rebuild and use. This condenser checker box/chassis looks like a decent platform for a standalone preamp, like a hotbox or similar. HT winding is 500vac and the original used a capacitive divider to cut the B+ in half. Any downside to this method/things to look out for? Do I need to balance the caps somehow? I don't think I have ever seen it done like this... 350vDC unloaded would be a much nicer place to start than 700... Any ideas or incite would be great. I have other power transformers that would be better, but would prefer to use the original if I can. Just enough heater current for a pair of 12SL7s.

heathkit condenser checker schematic.png

(not my red circles, just the first schematic I found.)

[Phil_S]

Full wave choke input will give you 500 * .45 = 225VDC and 1.54 *5mA = 7.7mA. Almost any cheap 3H choke will do the job. I think this might simplify things. I'm a huge fan of repurposing. I like that you are trying to do something with it. If you want a little more than 225V, you can put the 55V in series with the 500V primary and that will get you to 250VDC which is probably a very good voltage for a pair of 12SL7's.

[maxkracht]

Thanks Phil. I gave that a shot, and I am getting voltages I like with a 5k load, but I don't think I can put up with the inductor buzz. It was shaking quite a bit, even clamped to the chassis. Tiny all metal box doesn't have enough room to hide that rattle and not much extra room for Iron anyway. Working with a 5x9" footprint.

[maxkracht]

Tried it again with a .02uf flyback suppression cap, no change. Swapped out the vintage mojotone 3H choke for a modern 4H choke and no more shaky shaky. I don't have any other 3H chokes to test if it is the value or the device itself. It's slightly rusty, but I thought It was unused. More junk that someone gave me, so maybe I only got that choke because it was faulty in some way.

I'm still curious about the original heathkit power supply. I am assuming a big part of it was inexpensive surplus parts, but curious about what they were doing and why, even if it isn't the best practice.