[AMPS] Help building mono band amp

Barry Kirkwood bjk@ihug.co.nz
Thu, 11 Oct 2001 10:15:33 +1300

similar 2x813 amp in older "Radio Handbook" by Bill Orr. A proven performer.
73 es gl.
Barry Kirkwood PhD ZL1DD
Signal Hill Homestay
66 Cory Road
Palm Beach
Waiheke Island 1240
----- Original Message -----
From: Mike Baker <k7dd@qwest.net>
To: AMPS REFLECTOR <amps@contesting.com>; Jean-Michel Bombar
Sent: Thursday, 11 October, 2001 6:36 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
> 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
> will give you a comfortable KW out at 2.5 to 3KV.  For up to say 750 out
> could use two tubes and have an easier time finding the filament
> transformer.  (10VAC at 10Amps for two tubes)  Used a surplus 150pf cap
> my tuning on 40M and made the coil out of copper tubing.  The power xfmr
> 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
> 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
> 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
> not respected and the rules of working around it obeyed to the letter.
> 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
> 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
> 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
> loop shaped like a large fish hook with a wooden handle and a piece of
> with and alligator clip on one end clipped to ground.  Today I would
> 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
> 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
> 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
> 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
> love.  My personal feeling is that it should be taught in junior high
> and a requirement for a drivers license. It could greatly reduce the risk
> death to thousands.  Remember, electrocution causes the heart to stop and
> CPR applied immediately after the victim is clear of the danger can make
> 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
> 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
> 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
> 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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> >
> >
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FAQ on WWW:               http://www.contesting.com/FAQ/amps
Submissions:              amps@contesting.com
Administrative requests:  amps-REQUEST@contesting.com
Problems:                 owner-amps@contesting.com