John,
In addition to the high voltage diodes 6A10 mentioned earlier, rated
for 1 kV PIV, 6A DC and 400 Amp surge, another useful part for high
power is the M7P5 from Edal Industries. These are rated 1.5 kV PIV,
6A DC and 250 Amp surge. We use them in some very large HV power
supples (anode charging supply for 200 kW pulsed tetrode). Edal
quoted $6 a piece for 50 pieces.
Doesn't sound very attractive, IMHO. A quick check at Digikey shows that
in quantities of 50, the 1N5408 is $0.27 a piece, the 6A10 is $0.34, and
the FFPF10F150STU (1.5kV, 10A, fast recovery, but only 100A surge) is
$0.96, among several other good offers.
If a 6kV 6A rectifier is needed, 4 M7P5 would cost $20, while 6 6A10
would cost barely over $2. And the surge rating for the 6A10 is better.
Seems like there isn't any point in using the M7P5, unless they have
some other, important advantage.
This situation is typical in the electronic marketplace. Some specific
components become so common that mass manufacture makes them really
cheap, while other parts don't make it and never come down in price.
When designing, it's a good idea to use very common parts, as far as
possible, because these will remain inexpensive and available for a long
time, while parts that are less common may disappear from the market, or
get unreasonably expensive, forcing a design change to stay competitive.
Not a worry for a ham, of course. We have the luxury to use whatever our
junk boxes contain, without worrying much about the future availability
and cost of the parts!
Manfred
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