[GreenKeys] Re: TT1F/TXC-1 and PP-86E fuses blew !!!

[Craig Sawyers]

> One thing to remember about installing diodes in place of vacuum
> rectifiers is that diodes only have about .7 volt drop across them in
> the forward direction. A high vacuum rectifier can have many,
> many times
> that, and so when you tack in the diodes, you actually raise
> the output
> voltage of the power supply. This could cause consternation (and thus
> failure) in such things as filter capacitors.
>
> Keeping tubes where tubes were originally installed is not a bad
> practice.

The current through a vacuum tube rectifier goes at V^3/2, and is therefore
a rather soft characteristic as compared with a silicon diode which has an
exponential current characteristic.  The conventional approach is to try and
approximate this characteristic by using a silicon diode and series
resistor.  The value of the resistor to best match the tube characteristic
is best done graphically - if you know the tube number, google it or use the
excellent free program to be found here http://tdsl.duncanamps.com/ to
locate the datasheet.

Craig