help with plate supply

[jarthel]

Here's the schematic for one of the channels -->> http://home.swbell.net/acavalli/images/MJ_Headphone_Amp.gif

Here's the schematic for the supply -->> http://home.swbell.net/acavalli/images/MJ_Power_Supply_2.gif

When I simulated the plate supply (though without the 470K resistor as I can't put it) using Duncan's PSU designer, the the voltage across the last capacitor is around +200V. The load I used is a constant current of 27mA and this is according to the designer.

So I went and build the plate supply according to the schematics.
Well results are confusing. The voltage across the capacitors are:

1st = +350V
2nd = +350V
3rd = +350V

Can someone explain?

Maybe it's because that I need to build the amp first and connect it to plate supply and then I can measure the voltages across the capacitors and get correct readings?

Thanks for the reply.

Jayel

 

[SY]

You're not loading the supply at all, so the voltage will be higher than the fully-loaded voltage. Simulate a load by figuring out what the expected current draw of your amp is and using Ohm's Law to calculate the equivalent resistor, assuming you want 200V at the output.

The usual warnings apply. The voltages here are potentially lethal and must be treated with respect. if you don't know EXACTLY what you're doing, DON'T DO IT.

 

[jarthel]

current draw is 27mA per channel so it's should 54mA. How do I simulate current draw? Resistance load is easy but I have had to use current load in the past.

Thank you.

jayel

 

[SY]

I'm not sure what you're asking. If you expect a 54 ma current draw at 200 volts, calculating an equivalent resistor is straightforward. If you don't know how to do that and to determine the resistor's wattage, you shouldn't be messing around with high voltages.

 

[jarthel]

I was dumb to ask that. forgot about ohm's law.