857B and related

Mike Langner mlangner at SWCP.COM
Wed Apr 21 21:26:09 EDT 2010

Hello, boatanchorites !

The 857B rectifier is about 2 1/2 to three feet tall, and is rated at lots
of volts and lots of amps.  I used to use 6 of 'em in an RCA 50 kW AM
broadcast transmitter, a BTA-50E.

Not to be confused with 872 rectifiers, a pair of which is good for about a
kilowatt or two.

Since mercury has been declared a hazardous substance, what few high-powered
stations may have had some around have usually gotten rid of them -- along
with their PCB capacitors.

It's against the law to ship mercury by air, so many carriers won't accept
mercury-bearing packages.  Mercury quickly "rusts" aluminum by penetrating
the clear oxide (sapphire) thin surface layer that protects aluminum from
deteriorating.  Not good on an airplane.  Do a Google search for "mercury
rusts aluminum" and you'll get vivid reports on how fast it can destroy
aluminum.  But I digress.

Gary -- if you'd like me to put a request on the Society of Broadcast
Engineers listserver on your behalf looking for an 857B I'll be happy to do
so for you -- just let me know!

Certified Professional Broadcast Engineer

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