[Amps] HV Diodes

[Manfred Mornhinweg]

Carl,

 > Suffice it to say that the real world of tube type ham amps uses the 1N5408
 > almost universally no matter what the configuration.

Do the Alpha 8410, 9500, 8406, and the 89 belong into the real world of tube 
type ham amps? I would say, they do. And they don't use the 1N5408 but instead 
use a potted bridge rectifier, rated at 5kV peak inverse voltage and 2A total 
forward current. I don't know with certainty what's inside it, but 4 strings of 
5 each 1N4007 diodes would have exactly those ratings. Instead a bridge made 
from 1N5408 diodes would have a rating of 6A total.

This is it:

http://www.rfconcepts.com/REPLACEMENT-PARTS-LISTED-BY-ALPHA-PRODUCT/Blowers-and-Fans_2/HV-Bridge-Rectifier

Maybe it doesn't use the 1N4007, but then certainly it uses some other diode 
very similar to it, and not at all like the 1N5408.

They rate it for 50A surge of 8.3ms duration, which might mean the diodes inside 
are slightly beefier than the 1N4007, or maybe the difference is just due to to 
larger thermal mass thanks to the potting. If different, this could be 1N5622 
diodes, which have that 50A surge rating. But that diode has a slightly higher 
voltage drop, which isn't consistent with the bridge's rating for voltage drop - 
while the 1N4007's is consistent with it!

I suspect this bridge is simply made from 1N4007 diodes, nicely potted, and sold 
for $150...

Take $2 worth of diodes, a little plastic case, 4 blade terminals, 20 drops of 
solder, and a few grams of a good epoxy potting resin, put it all together, and 
sell it for $150 to hams.  Hmm, I should get into that business! ;-)

On the other hand I do admit that several other amps I checked, indeed use 
bridges made from 1N5408 diodes. But the Alphas are too important an exception, 
to ignore them!

Manfred

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