900v. 100ma. Power supply for 813 tube amplifier

[SY]

You series diodes (with voltage equalizing resistors across them) to form a diode with a higher working voltage. For example, two 1000V diodes in series would form the equivalent of a 2000 volt diode. The only difference between that composite diode and a "genuine" 2000V diode is that the composite will have two times the voltage drop, i.e., 1.4V rather than 0.7V.

[fdegrove]

Hi,

two times the voltage drop, i.e., 1.4V rather than 0.7V.

Due to that they are a little better at surviving inrush current surges and yes, the spikes are a little less pronounced than on a single diode too.

In the circuit as shown by George they're used in a voltage doubler so the 1N4004 being a 400V 1A device wouldn't have a chance when left on its own there, hence the 2 diodes in series making it essentially a 800 Fv device at 1A and 800V PIV but with a Fvd of 1.4V iso 0.7V as SY has pointed out.

Cheers,