Date: Sat, 07 Jan 2017 21:30:23 +0000
From: Manfred Mornhinweg <manfred@ludens.cl>
To: amps@contesting.com
Subject: Re: [Amps] Decline of homebrewing?
Steve, and all,
I was nearly killed at age 15.
## heres my sob story. I was building a heath GR-64 SW rx between xmas +
new year 1969. Age 14
My mum was cooking dinner, and I was in the den, just off of the kitchen. I
had just finished building the
kit after several days..and a had 3-4 components left over. Thought to myself
that heath was not too smart to
be supplying parts that were not required. Of course, when plugged in and
turned on.... it was dead silent.
I take off the lid, and flip it upside down.... and this is a tube RX. I
start probing around...with my fingers....with zero test gear,
then got zapped with 300 vdc off one of the filter caps..it was unplugged too.
Let out a scream, and went flying across the room. Mother
freaked out, and figures Im in way over my head, and has a fit. Being from
the UK, she thinks nobody should touch anything unless
they have 1st completed the 7 year apprenticeship in the appropriate field.
My older sisters boyfriend at the time was a physics
lab instructor at the local university, and had a lot of experience with HB
electronics..and also fixing every heath / dynaco / knight kit in town.
He fixes it in a few hrs, and all is well. 3-4 components were indeed required.
## fast forward to 1974. Bought a used HB 2 x 813 amp..with NO B+
voltage meter. Great fun driving it with 200 w po from my used
drake TR-3 xcvr. 1100 w out. Nobody even knew what IMD was back then, and
could care less. I short out the filter choke on the fully exposed
B+ supply, for even more B+.
## wanting more power, around 1976, I buy a used HB single 3-400Z rf
deck, no cabinet, no B+ meter, and no B+ supply. I build a hb 5 kv no load
B+
supply, and also cabinets for both the B+ supply + the RF deck. Filter caps
were a mess of series and parallel 2-4-6 uf oil caps....and no bleeder.
Drove the
3-400 Z with the TR-3. No tuned input on the rf deck. 1700 w out of a single
3-400Z. Tube ran bright orange to sorta yellowish.
Was working out of town those days, a week at a time. B+ supply had been
OFF from sunday eve to the following friday night. 4 inch diam muffin was
sorta loose,
so tightened it with an xcelite nut driver. Tube was in the way, so tried
to work around it. Tried tightening the top pair of corner screws, and shaft
of nutdriver
was touching the glass. Shoulda yanked the tube but was in a rush, contest
on that weekend. To get the driver to fit, I slide my fingers down onto the
steel nutdriver shaft,
and try to get the nuts tightened. Wearing a T shirt with bare arms exposed.
Nut driver shaft touches the plate cap of the 3-400Z..and also had both
forearms resting on the
aluminum box. Top lid was removed. I get thrown 7 feet across the room,
and wake up 5 mins later..dripping in sweat.
## lesson learned was oil caps will stay charged for at least 5 days..... esp
when stupid enough to not include a bleeder.
After that it was B+ meters wired in both the RF decks and also the external
B+ supplies. Bleeders used, and ditto with shorting sticks etc.
## Got zapped a few times while working at the telco....and each time was up
7-10 feet off the ground on a rolling ladder. AC is bad news.
B+ will throw you across a room..and both will easily kill you. Had a buss
bar explode in my face while trying to pry a stuck fuse out. Blew
a hole in the square shaft of the large screwdriver I was using at the time.
I almost had it out when the shaft touched the partially recessed mounting screw
for the insulator block assy..in the rack. I had shorted the input buss side
of the bank of fuses. Now you know why there is at least one guy in every
telco office nicknamed ..... sparky.
Jim VE7RF
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