Grounded, Floating, or Thermistor-To-Case for Center Tap

[luvdunhill]

so, I currently have a 175VAC x 2 toroid that I'm using to get 350VAC. I just put the two secondaries in series. I haven't grounded the center tap (is it even technically a center tap?) but just tucked it away. What's the recommended thing to do here for safety?

[kevinkr]

Originally posted by luvdunhill
so, I currently have a 175VAC x 2 toroid that I'm using to get 350VAC. I just put the two secondaries in series. I haven't grounded the center tap (is it even technically a center tap?) but just tucked it away. What's the recommended thing to do here for safety?

I assume you are using this with a full wave bridge rectifier? Electrically this is a center tap, however you do not have to make use of it. If so the correct thing to do is to insulate it well and tuck it out of the way. Do not ground it!

[luvdunhill]

Originally posted by kevinkr



I assume you are using this with a full wave bridge rectifier? Electrically this is a center tap, however you do not have to make use of it. If so the correct thing to do is to insulate it well and tuck it out of the way. Do not ground it!

yes, I should have mentioned that. I'm using four diodes.

[luvdunhill]

one other question What sort of transformer could be used with a pair of TV Damper Diodes to rectify this to around 490VDC with a good amount of current, say 200mA? Any schematics that you could point me to? I'd like to learn a bit more about this way of doing things

[zigzagflux]

Sheesh, that's a beefy power supply you're talking about, 100W. I sure hope it's to be used as a stereo supply !

Attached is my current monoblock project; bottom supply provides 500V at about 125mA, ripple less than one volt. You can use very similar values for choke and capacitors, but will probably have to increase your transformer current rating to almost 300mA = 165VA.

http://www.just4sheep.com/site/docs/schematic.pdf

[luvdunhill]

Originally posted by zigzagflux
Sheesh, that's a beefy power supply you're talking about, 100W. I sure hope it's to be used as a stereo supply !

Attached is my current monoblock project; bottom supply provides 500V at about 125mA, ripple less than one volt. You can use very similar values for choke and capacitors, but will probably have to increase your transformer current rating to almost 300mA = 165VA.

http://www.just4sheep.com/site/docs/schematic.pdf

something doesn't seem right. that's a single 550 VAC winding and around 20 V drop for each tube? Seems low. Probably due to small capacitor before inductor, and not a pure capacitor input filter? Just interested in seeing the math, I suppose. PSUD2 is at home unfortunately, so perhaps I'll play with this tonite and see what I come up with Also, the 6CG3 looks like it can provide even more current capacity, but has hungry heaters...

[zigzagflux]

Those values and outputs are right on the money; power supply is already built and tested. PSUD is amazingly accurate when used properly.

To each his own, but I am not a big fan of largish-C input filters. This is sort of a hybrid between choke and cap input filter. Selection of the first C allows for waveshaping of the current and reduces nasty dv/dt transients generated from a pure choke input filter. Also allows some customization of the actual output voltage for larger values of C, say 1-5 uF.

What are you planning on running with 500V 200mA ?? Pray tell.