Really good advice, Mike... you usually don`t get a second chance with hv
equipment.This is certainly something first time amp constructors (and
seasoned vets as well!) should put first on the safety list!
73 to all, Jim, K7RDX
----- Original Message -----
From: Mike Baker <k7dd@qwest.net>
To: AMPS REFLECTOR <amps@contesting.com>; Jean-Michel Bombar
<jmbombar@graphnet.fr>
Sent: Wednesday, October 10, 2001 10:36 AM
Subject: Re: [AMPS] Help building mono band amp
>
> Hello,
> Get an ARRL handbook from say, 1965. For several years there was an
> article on building monoband KW amps using a pair of 813's. I used these
> articles as the basis for my very first amp in 1969. 813's are still
> available via various sources including the internet and are quite
> inexpensive. I scrounged around for a year or so on e-bay and made a deal
> with a fellow to buy 9 tubes and 4 sockets for $80 including the shipping.
> 7 tubes were carbon plates (the best ones IMHO) and 2 were the metal
plates.
> One broke in shipping (not carbon,no loss). For any band up to 20 meters
> they kick butt and love high voltage. The book specs say 2500VDC max for
> the plates but up to 3500VDC is commonly used in GG linear service. 4
tubes
> will give you a comfortable KW out at 2.5 to 3KV. For up to say 750 out
you
> could use two tubes and have an easier time finding the filament
> transformer. (10VAC at 10Amps for two tubes) Used a surplus 150pf cap
for
> my tuning on 40M and made the coil out of copper tubing. The power xfmr
was
> a surplus unit that ran 900VAC at 1A as a voltage doubler.
> Total cost back then (1969) was maybe $30 but you could still build
one
> today for less than a $100 with a little patience and scrounging. The best
> part of building is you get to test and refine a bunch of talents. Sheet
> metal fabrication, wiring or harness making, parts recognition and
purchase,
> electronic design, metal finishing/painting, etc. just to name a few.
> A few caveat come to mind. I mention these to anyone who is
> contemplating building their first amp.
> 1. HIGH VOLTAGE is not just a sticker on the side of a cabinet. It
> is a seductive lover that will KILL you and bring you to room temperature
if
> not respected and the rules of working around it obeyed to the letter.
You
> seldom get a second chance let alone a third to violate the rules. I have
> been blessed with having survived lethal shocks twice and figure that a
> third is not likely so be aware.
> DO NOT put your hands inside a cabinet that has High Voltage (anything
> above 24Volts AC or DC) present. The AC power mains kill more people
every
> year than any other type of electrocution.
> Work with one hand in your pocket. NOT leaning on a grounded metal
> cabinet or desk.
> Always disconnect the mains power and flag or wrap up the plug end so
it
> isn't accidentally reconnected by someone else. (The old story about two
> guys working on a transmitter together and as one guy has his hands inside
> the cabinet, the other finds the plug pulled from the mains and plugs it
> back in without thinking, saying something like, "OH, I found the problem,
> it isn't plugged in; try it NOW!" Room temperature.
> Use a "shorting" stick or discharge stick. In days of old a large
metal
> loop shaped like a large fish hook with a wooden handle and a piece of
braid
> with and alligator clip on one end clipped to ground. Today I would
modify
> that to be a probe type of stick with a non-conductive handle hooked to a
> long string of 2 watt metal film resistors with a total value of about
100K
> Ohms or so. Use it to check the discharged state of the HV caps before you
> start working on the amp.
> Use a shorting clip across the HV to GND and remove it when you are
> done. IF, IF someone accidentally turns on the power while you are inside
> the cabinet, it will/should blow the FUSE or Circuit Breakers and keep you
> from being a dead fish.
> NEVER, NEVER build an amp without proper fusing of the mains.
> NEVER, NEVER bridge the safety devices (fuses or breakers). They have
a
> purpose.
> NEVER, NEVER work on a project involving High Voltage while you are
> exhausted or overly tired. Falling asleep into your work can be deadly.
> Too tired and you do stupid things you might never recover from.
> NEVER, NEVER work on a project involving High Voltage if you are
> intoxicated. Same result as the previous warning. Save the 807's for the
> celebration of a successful days work.
> All of these previous warnings are old hat and inevitable truths to
> staying alive while working around High Voltage as I am sure most would
> agree. Let me add a couple of my own.
> Realizing that the Human nature of things is to do something as long
as
> you can so long as it doesn't hurt you, all of us at some time or another
> have violated one of the rules listed above. Some of us have survived the
> experience. Some of us had Help surviving the experience.
> If you don't know CPR go and learn it. Once you do you will posses a
> skill that you may never have to use (hopefully). But the alternative to
> not knowing it may cost someone their life and it just might be someone
you
> love. My personal feeling is that it should be taught in junior high
school
> and a requirement for a drivers license. It could greatly reduce the risk
of
> death to thousands. Remember, electrocution causes the heart to stop and
> CPR applied immediately after the victim is clear of the danger can make
the
> difference in being back to normal or a "gomer".
> If you must work on a piece of equipment that involves high voltage do
> NOT do it alone. Be sure someone knows where you are and what you are
> doing. Have a buddy give you a hand. (It can be more fun doing these
things
> as a "buddy" project.) There is nothing more unnerving than to have your
> wife come home and find you "well done" and at room temperature out in
your
> garage or in your shack. It ruins their day and yours!
>
> OK, I know this all seems like I am describing the obvious, but it is
> worth repeating.
> It is sort of like meeting a beautiful woman in a club. YOU ONLY GET
> ONE CHANCE TO MAKE A GOOD FIRST IMPRESSION! You will seldom get a second
> chance.
>
> Good luck with your amp project. READ, READ, READ, and if you still
> have questions, at least you know where to ask. In spite of all of the
> banter and sniping at each other on occasion, this is still one of the
best
> resources for information on AMPS. You could never say this group isn't
> passionate about what they are doing.
> Again, good luck.
> Mike Baker K7DD
> k7dd@qwest.net
> ----- Original Message -----
> From: "Jean-Michel Bombar" <jmbombar@graphnet.fr>
> To: <amps@contesting.com>
> Sent: Wednesday, October 10, 2001 12:57 AM
> Subject: [AMPS] Help building mono band amp
>
>
> >
> > Hello,
> >
> > I would like to built my first HF amp, I am thinking of a 1Kw mono band
> amp
> > for the 40M band.
> > Does any of you have any idea of where I could gather informations to
> start
> > this project?
> >
> > Thanks.
> >
> > Jean-Michel, F5MMX
> >
> >
> > --
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> > Problems: owner-amps@contesting.com
> >
> >
>
>
> --
> FAQ on WWW: http://www.contesting.com/FAQ/amps
> Submissions: amps@contesting.com
> Administrative requests: amps-REQUEST@contesting.com
> Problems: owner-amps@contesting.com
>
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