Date: Wed, 22 Feb 2023 22:18:28 -0700
From: John Lyles <jtml@losalamos.com>
To: amps@contesting.com
Subject: [Amps] 10 KW CCS ON 6M...USING THE 3CX-6000A7... PART 16
<Jim, you could subtract your meter lead resistance from each winding
<measurement, its even better. Also, notice that the value of R slowly
<dropped. This is because the secondary is resisting the step change flow
<of current, just like a capacitor resists a change in voltage. Be
<careful about having hand on each probe as there might be kick, the EMF
<from disconnecting that continuous current. It used to be much worse
<when using a Simpson 260 VOM. Don't ask me how I would know that.
<That is an awfully heavy iron part to place on a sheet metal chassis
<bottom. It might help to add some flat stock across from end to end,
<like 2 inch wide aluminum bars. This spreads the load and prevents
<dimpling of the sheet metal. In commercial transmitters with even
<smaller transformers, we used 3/8 steel plate for the bottom and drilled
<holes, welded nuts on the bottom for bolting the iron in. This also had
<some I beams welded to it, so that a pallet jack or fork lift could move
<it. That would be overkill for yours.
<73 John
K5PRO
## See part 17 that I just posted. Underneath side of aluminum base plate
is now re-enforced with 2 x sheets of 3/4" thick plywood. So now it's
1.5" of plywood beneath it...doesn't budge or flex.
## On my own latest B+ supply, I used a surplus 19" wide x 31" deep x
34" tall rack cabinet. HD steel, like 12-14 ga steel through, including
the base. To re-enforce the base, I installed a huge sheet of 1/4" thick
6061-T6 plate ( corners notched) on the top side of the steel bottom.
Below the steel bottom, I installed a 31" length of uni-strut, right down
the middle of the cab. Then a short aprx 8"piece of uni-strut, dead
center, on either side of the main 31" uni strut. 31" uni-strut runs
N-S. Short pieces run E-W. Uni-strut makes thick steel T shaped plates,
to join the N-S and the EW ends together.
## at the extreme N-S and also E-W ends of the uni-strut, they are simply
bolted from below..and go up through the uni-strut, then the steel bottom,
then the 1/4" thick alum plate. Can't have any bolts near the plate
xfmr. The 253 lb dahl uses 2.5" x 2.5" x 1/4" thick angle steel, 2 of
em, running N-S. The only bolts in the middle are the 4 x bolts, that
bolt the xfmr, right through to the under side. 4 x 200 lb rated casters
used. I use the type that swivel 360 degs..and no brakes on em, pita.
Then the entire supply spins 360 degs, and also side to side, or front to
back, or diagonally, on an angle.
## On my other B+ supply..... built by local RI no less, he used a pair of
4" wide channel aluminum pieces, ( 4" wide, with 2" lips), flipped upside
down, to support the weight of the pair of 80 lb hammond plate xfmrs.
## There is a few other methods used to support the weight of either the
heavy xmfr, or the net weight of everything installed into a rack cabinet.
The uni-strut method worked slick, dead simple., and adds extremely little
weight to the entire mess.
## I had plenty of alum plate, so used it. I wanted the alum base plate
for a solid grounding point. Too much grief in the past, trying to use
painted steel.
## On my pair of new hammond 24" wide x 24" deep x 70" tall commercial rack
cabinets, they come with welded corners and optional casters, so used em.
They come with brazed / welded threaded silver plated copper bolts sticking
out from main vertical steel frame rails, for grounding. No xfmr's in
either rack. But one of em has the 127 lb, Dahl, 4 H choke in it, ( used
in a C-L-C config). Installed 2 x 2 angle alum down each side at the very
bottom, then 1.5" thick plywood sitting on top of the alum frame rails.
Then a pair of 4" wide, inverted channel alum rails, butted together, to
support the Dahl choke. Choke bolted to the flat side of the pair of alum
channel pieces..with just 4 x 1/-20 SS bolts into the tapped holes in the
channel. At extreme ends of each 17" channel alum, 4 x glastics used,
2.5" diam x 2.5" tall, with 3/8" embedded threads. Bottom of glastics is
bolted to the 1.5" thick plywood. (painted black).
## I wanted the choke in the B+..and not the B-. The problem with any
choke in series with the B- is..... any V drop, across the choke just adds
a ton of extra, unwanted bias to the GG Triode. Choke measured 9.56 ohms,
and with 1.5 to 3.0 amps flowing through it, the V drop across it = 15-30
vdc.
## also installed a hb adjustable spark gap across the choke terminals (
1/4-20 brass threads and solid brass acorn nuts, with acorn nuts facing
each other). Also a real HD spst, square ceramic Kilovac relay across the
choke terminals. Then, if required, choke can be shunted.
## also used the same / similar HB spark gaps ( 8-32 or 10-32 hardware)..
across both the vac tune cap..and also the vac load cap. The one across
the tune cap also protects the bandswitch.
Jim VE7RF
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