[Amps] Alpha 77Dx Filament Mod Update
Paul Christensen
w9ac at arrl.net
Mon Feb 2 11:52:11 EST 2009
Quoting myself:
> "Thankfully, the fix is simple and doesn't even require removing a single
screw from these amps. The chassis and neutral can be un-linked by cutting
a jumper at the Cinch-Jones power plug. Then, the three-wire power cord is
replaced with a four-wire cord in a (L1-L2-N-G) configuration. Now, neutral
and chassis ground are safely disconnected and meet NEC criteria."
What I failed to mention is that four-wire service must then be run from the
serving load center into the shack and a new 4-wire outlet installed. So,
if you've got three-wire service (L1-L2-G) with no neutral running into the
shack, changing that out to at least #10/4 can be a real job. I did it a
few years ago on a hot sunny day in Florida when upgrading the service
through the attic. Not one of my most pleasurable moments in life.
For the wall outlet, I went with a 30A isolated-ground Hubbell Twist-Lock as
I had it on-hand. No real need for the I/G model, especially if using
plastic rework electrical hardware.
Paul, W9AC
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