[Johnson] Warning about high ac line voltage.

[James M. Walker]

One suggestion would be to acquire several variable transformers, commonly
known as "Variacs", some types are also auto-transformers, and some types
come in a package with meters for voltage and current. Those are expensive
however. The standard variac type turns up all over the place. What you
would
need for your transmitter type may vary as to current, try for a little
excess ability
in the units you get.

I run my DX-100 type transmitters on the 15 Amp version, receivers singlely
can
run on the 3 Amp version, or you can use a 10 - 15 and plug all your
receivers
into a "Waber" strip fed by the variac. I have acquired 0 -150 VAC meters of
several manufacturers and mounted them in boxes and monitor the line voltage
to the rigs that way. Fluctuating line voltages is not a real problem with
these things.
I even run my BC-610s and T-368 off of separate variacs, and I run my RCA
BTA-1M off of a 0 - 240 VAC 45 amp (theater light controller) variac. They
work
great, and relieve you of the concern for burning up power transformers in
the "GB"
equipment. FWIW

Jim
WB2FCN
http://eshop1.chem.buffalo.edu


----- Original Message -----
From: "Sherrill Watkins" <Sherrill.Watkins at dgs.virginia.gov>
To: <johnson at mailman.qth.net>
Sent: Wednesday, October 06, 2004 9:08 AM
Subject: [Johnson] Warning about high ac line voltage.


Gentlemen: I happened to be reading the book entitled "Care and Feeding of
Power Grid Tubes" published by Eimac in 1968 and noticed something
interesting. Eimac states that for power grid tubes an increase in the
filament voltage of just 3 percent over the rated filament voltage can
reduce
the tube life by as much as 50 percent!! (Please don't argue with me about
this. I suggest to obtain a copy of the book and read it.) My measured ac
line voltage is about 5 percent over the U.S. Standard of 120 vac.
Therefore,it may be reasonable to presume that any vacuum tube equipment
operated on a line volatage of 125 vac will have a filament voltage that is
5
percent higher than the rated filament voltage. -73- Sherrill W. k4own
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