My knowledge of vacuum tubes and kV power supplies is limited. I have
been reading an article in the ARRL Handbook detailing the construction
of a 1kW HF Linear. I'd like to try my hand at building something like
this. I found the article a little intimidating: Ceramic insulators,
parasitic suppressors, thermal and mechanical engineering etc. Is
there some book that details this type of thing with an explanation of
the whys as well as the whats and hows. My priorities a

1) Safety. I'd like to be alive to make my first 1kW QSO
2) Avoiding equipment destruction, arc overs, black smoke, explosions
etc
3) Safetly troubleshooting this kind of equipment, loading testing
etc.
4) How to deal with tubes: warm up, care, etc...
5) Avoiding TVI (ITV), parasitic oscillations etc.
6) Longevity and Duty Cycle issues etc.
7) Costs and sources.

Hope someone can help.

Thanks,

Tim

On Wed, 13 Jul 2005 wrote:

Date: 13 Jul 2005 14:05:17 -0700
From:
Newsgroups: rec.radio.amateur.homebrew
Subject: QUESTION: Fun with Svetlanas or Staying alive with kV power supplies

My knowledge of vacuum tubes and kV power supplies is limited. I have
been reading an article in the ARRL Handbook detailing the construction
of a 1kW HF Linear. I'd like to try my hand at building something like
this. I found the article a little intimidating: Ceramic insulators,
parasitic suppressors, thermal and mechanical engineering etc. Is
there some book that details this type of thing with an explanation of
the whys as well as the whats and hows. My priorities a

1) Safety. I'd like to be alive to make my first 1kW QSO
2) Avoiding equipment destruction, arc overs, black smoke, explosions
etc
3) Safetly troubleshooting this kind of equipment, loading testing
etc.
4) How to deal with tubes: warm up, care, etc...
5) Avoiding TVI (ITV), parasitic oscillations etc.
6) Longevity and Duty Cycle issues etc.
7) Costs and sources.

Hope someone can help.

Thanks,

Tim

When I was a kid, I was building 10kV HV transformers, 100kV Tesla coils,
spark coils, discharging HV capacitors that make "bangs" about as loud as
medium sized firecrackers, smoked resistors, shorting outputs on 100 amp
transformers just to see the sparks fly, etc., and so I have an intuitive
feeling for various stuff. I've gotten shocks maybe a dozen or two times
in my life. Nasty. Most of the time these were from a finger to thumb and
not through my heart. When current was involved, I'd get a button of
burned flesh on my skin and that really hurts plus burnt flesh really
stinks like almost nothing else except dead flesh that has been dead long
enough at room temperatures to really stink. RF burns...you don't
feel the pain (which also really hurts) until after the burn and you get
that burnt flesh stink, too. Even from 50 watt rigs they can be bad.

My experience includes mechanical devices, electric drills, bolts and
nuts, threaders, chassis punches, electric drills, band saws for cutting
metal sheets, etc.

If you have never done anything "hands on" in your life, then your grand
plan dream may be an undertaking that you would be wise to avoid. On the
other hand, if you are mechanically inclined and practical and NOT a klutz
(definitely not a klutz), then I'd suggest starting with a smaller
and easier project and then move up.

At points where you start working with lethal voltages and currents, you
do need to be careful. Very very careful. They say when the power is on
and the cabinet is open, you need to keep one hand in one of your pockets.
Stand on a piece of dry wood at least 1/2" thick, etc. Yes, arcs and smoke
can be intimidating. Just the surprise from an arc can make you jump in an
unpredictable way and if not hurt yourself from the electrical shock, then
you'll bang your head or something else.

Parasitic oscillations and TVI: At least start with a KW level dummy load
and know what the book says about neutralization and how to test for it
and adjust it. Also, you cannot have enough meters to measure everything.
Even filament voltage and current. I'd have a meter for every circuit:
plate, screen grid, control grid, cathode current, and voltages on all of
them.

Weirdest discoveries: serious RF noise from solid-state diodes. Also,
serious RF noise from HV transformers (output connected to
absolutely nothing, but AC on primary and can hear the noise across the
SW band). Weirdest lightning effect: blew out a very big (1 kW) plate
transformer (2200-0-2200 v) and bypass capacitors to ground and nothing
else in the hamshack was affected (collins S line, Drake twins, ten tec
rig, etc.).

Key warning: know what you can and can't get away with using HV silicon
diodes.

Building your own gear: I have had no sense of pride, accomplishment, and
usefulness like building my own. Especially from junk in the junk box. My
biggest rigs were 500 watt linears using 4-400As, and a few others. Built
kits (Knight, Heath [too bad they are not around any more]), too.

W4PON

wrote:
My knowledge of vacuum tubes and kV power supplies is limited. I have
been reading an article in the ARRL Handbook detailing the construction
of a 1kW HF Linear. I'd like to try my hand at building something like
this. I found the article a little intimidating: Ceramic insulators,
parasitic suppressors, thermal and mechanical engineering etc. Is
there some book that details this type of thing with an explanation of
the whys as well as the whats and hows. My priorities a

1) Safety. I'd like to be alive to make my first 1kW QSO
2) Avoiding equipment destruction, arc overs, black smoke, explosions
etc
3) Safetly troubleshooting this kind of equipment, loading testing
etc.
4) How to deal with tubes: warm up, care, etc...
5) Avoiding TVI (ITV), parasitic oscillations etc.
6) Longevity and Duty Cycle issues etc.
7) Costs and sources.

Hope someone can help.

Thanks,

Tim

I built a homebrew KW about 15 years ago using a pair of 4-400 in
grounded grid. It worked fine on 80-20 but I never did get the tank
Q adjusted well enough for good output above that. Not that it couldn't
have been done with a bit more tinkering.

The power supply put out about 4000 volts no load. I used a time delay
circuit with a relay and a power resistor to limit the in-rush current
while the capacitor filter bank charged. It had a relay whose ac coil
was across the primary of the plate transformer that shorted out a power
resistor in series with the primary. As the caps charged and the input
current fell so did the voltage drop across the power resistor until the
primary voltage rose to the relay's pull in voltage shorting out the
resistor. (Idea from ARRL HB).

A second time delay circuit did the same thing for the filaments of the
4-400's. This relay also locked out a second relay that applied power
to the plate transformer. Result, the plate supply couldn't be turned
on until the 4-400 filaments were warm, that delay was about 1-2 seconds
during which a power resistor in the filament transformer primary
limited the 4-400 filaments to half voltage.

The filter caps were 10 330uf 450v computer grade units in series, each
cap bridged by a 50k 25W power resistor to even the voltage across the
caps and act as a bleeder resistor. A 1ma meter with a suitable
multiplier resistor in series served as a voltmeter across the
capacitors (I forget how many meg ohm it was). The meter case was
thick enough plastic to be insulated enough from the chassis (and
and besides the main plumbing was behind several meg ohms). The meter
read 5000v full scale.

I always assumed there was voltage across the caps when I worked on the
rig. First pull the plug(s). Wait till the voltmeter drops to zero.
THEN put a heavy screwdriver with a well insulated handle from ground
to the HV terminal to be sure! (I used to do that to picture tubes
when working on tv sets). Keep on hand in the pocket if you need to
adjust anything when it's hot. BTW an RF burn can be more deadly than
a DC jolt. (Think microwave oven).

HV isn't the only thing that can get you. High current can give you
a nasty surprise. Like the guy replacing some batteries on a golf cart.
He was using a ratchet wrench to tighten the battery clamps and he
ended on the most positive battery terminal. The handle of the wrench
hit the chassis of the golf cart putting it between 36 volts and ground
of some VERY HEAVY DUTY batteries. Ever see a Sears ratchet wrench
glow WHITE HOT? (and melt?)

straydog wrote:
. . .
arcs and smoke can be intimidating. Just the surprise from an arc can
make you jump in an unpredictable way and if not hurt yourself from the
electrical shock, then you'll bang your head or something else. . .

In a previous life, I was reaching way to the back of a cabinet of radar
equipment for some reason. I was lying on my stomach, my arm was
extended all the way, and my head was into the cabinet doorway about at
the forehead level, with a couple of inches clearance above and below.
Of course all the safety precautions were followed -- some of the heavy
ground radar stuff I worked on was easily lethal. But there was some
charged capacitor, something hot from another cabinet of gear, I don't
recall, and I got a minor shock. My instinctive reaction was to jerk my
head up, and it hit the top of the doorway. That hurt and made me
reflexively jerk my head downward, hitting the bottom of the doorway
with my forehead. That caused a jerk back upward, hitting the top again,
and so forth. There I was, oscillating up and down, beating my head to a
pulp, knowing exactly what was happening but helpless to do anything
about it. It continued for what seemed like a long time, until I was
sore enough that I couldn't feel one more whack, when I was finally able
to stop and extract my head and arm. I guess I've felt as stupid a few
times since, but only a few times.

And when you bend your arm every which way in order to get at something,
it might go in all twisted contorted, but it comes out fast and straight
when you get bit. I've lost a bit of skin that way, too.

Roy Lewallen, W7EL

Ken Scharf wrote:
The filter caps were 10 330uf 450v computer grade units in series, each

Probably dumb (and WAY off topic) question:

What's the *intended* purpose of a 450v "computer grade" capacitor?

--
Doug Smith W9WI
Pleasant View (Nashville), TN EM66
http://www.w9wi.com

On Thu, 14 Jul 2005, Roy Lewallen wrote:

Date: Thu, 14 Jul 2005 00:48:01 -0700
From: Roy Lewallen
Newsgroups: rec.radio.amateur.homebrew
Subject: QUESTION: Fun with Svetlanas or Staying alive with kV power
supplies

straydog wrote:
. . .
arcs and smoke can be intimidating. Just the surprise from an arc can make
you jump in an unpredictable way and if not hurt yourself from the
electrical shock, then you'll bang your head or something else. . .

In a previous life, I was reaching way to the back of a cabinet of radar
equipment for some reason. I was lying on my stomach, my arm was extended all
the way, and my head was into the cabinet doorway about at the forehead
level, with a couple of inches clearance above and below. Of course all the
safety precautions were followed -- some of the heavy ground radar stuff I
worked on was easily lethal. But there was some charged capacitor, something
hot from another cabinet of gear, I don't recall, and I got a minor shock. My
instinctive reaction was to jerk my head up, and it hit the top of the
doorway. That hurt and made me reflexively jerk my head downward, hitting the
bottom of the doorway with my forehead. That caused a jerk back upward,
hitting the top again, and so forth. There I was, oscillating up and down,
beating my head to a pulp, knowing exactly what was happening but helpless to
do anything about it. It continued for what seemed like a long time, until I
was sore enough that I couldn't feel one more whack, when I was finally able
to stop and extract my head and arm. I guess I've felt as stupid a few times
since, but only a few times.

And when you bend your arm every which way in order to get at something, it
might go in all twisted contorted, but it comes out fast and straight when
you get bit. I've lost a bit of skin that way, too.

Roy Lewallen, W7EL


Yep. Great story. Reminds me about that sad/funny joke about the guy, his
tower, bucket of tools in a wooden barrel, ropes, pully, and somehow he
goes up and down the tower, wooden barrel breaks so the counterweight
disappears and he goes down again....broken bones, cracked skull, all
kinds of hospital damage. Funny/sad. Similar to the chainsaw joke. Anyone
remember or have those jokes stored away somewhere that they can drag them
out?

I didn't think I had any "funny" jokes like the tower joke, etc., but I
definitely had some non-fatal "war stories" to tell. I also built a couple
of those "repulsion coils" as a kid. Aluminum ring & coat hanger wire core
& couple hundred turns of number 14 gauge wire, plug into AC line and the
ring would shoot up 1-2 feet. Neat. Playing around with a high turns coil
on it one day and didn't realize my fingers were on some terminals and I
must have gotten a thousand volts pressed against my thumb: ergo, two
burned spots on my thumb. And, that burnt flesh stench. Gawd did it stink.
And, it hurt like hell.

Radar? I've heard a couple of stories of guys who walked in front of those
dishes not knowing they were putting out KWs of microwaves and they got
their tummy microwaved into cooked beef. Killed em dead. Better have a
buddy around and you can ask him: "Hey, I think this thing is turned
off...Am I thinking right? Please go look at all the switches and check,
tubes lit up, fans running, hum from transformers, other noises? Please?"



Art, W4PON

Hi

On Thu, 14 Jul 2005 11:45:41 +0000, straydog
wrote:



On Thu, 14 Jul 2005, Roy Lewallen wrote:

Date: Thu, 14 Jul 2005 00:48:01 -0700
From: Roy Lewallen
Newsgroups: rec.radio.amateur.homebrew
Subject: QUESTION: Fun with Svetlanas or Staying alive with kV power
supplies

straydog wrote:
. . .
arcs and smoke can be intimidating. Just the surprise from an arc can make
you jump in an unpredictable way and if not hurt yourself from the
electrical shock, then you'll bang your head or something else. . .

In a previous life, I was reaching way to the back of a cabinet of radar
equipment for some reason. I was lying on my stomach, my arm was extended all
the way, and my head was into the cabinet doorway about at the forehead
level, with a couple of inches clearance above and below. Of course all the
safety precautions were followed -- some of the heavy ground radar stuff I
worked on was easily lethal. But there was some charged capacitor, something
hot from another cabinet of gear, I don't recall, and I got a minor shock. My
instinctive reaction was to jerk my head up, and it hit the top of the
doorway. That hurt and made me reflexively jerk my head downward, hitting the
bottom of the doorway with my forehead. That caused a jerk back upward,
hitting the top again, and so forth. There I was, oscillating up and down,
beating my head to a pulp, knowing exactly what was happening but helpless to
do anything about it. It continued for what seemed like a long time, until I
was sore enough that I couldn't feel one more whack, when I was finally able
to stop and extract my head and arm. I guess I've felt as stupid a few times
since, but only a few times.

And when you bend your arm every which way in order to get at something, it
might go in all twisted contorted, but it comes out fast and straight when
you get bit. I've lost a bit of skin that way, too.

Roy Lewallen, W7EL


Yep. Great story. Reminds me about that sad/funny joke about the guy, his
tower, bucket of tools in a wooden barrel, ropes, pully, and somehow he
goes up and down the tower, wooden barrel breaks so the counterweight
disappears and he goes down again....broken bones, cracked skull, all
kinds of hospital damage. Funny/sad. Similar to the chainsaw joke. Anyone
remember or have those jokes stored away somewhere that they can drag them
out?


That'd be http://monologues.co.uk/004/Bricklayers_Story.htm - at
least, that's the original one from Gerard Hoffnung - which dates back
a few years.

I used to play the tape of this as part of my 'Quality Awareness'
sessions - trying to make the point about forward planning, and
avoiding situations that are going to cause problems.....

There are further versions of this relating to towers and ham radio -
a google for Hoffnung + Bricklayer will turn them up

Probably funnier to read about than be involved with g

Take care
Adrian
Suffolk UK

======return email munged=================
take out the papers and the trash to reply

In article ,
Ken Scharf wrote:

I always assumed there was voltage across the caps when I worked on the
rig. First pull the plug(s). Wait till the voltmeter drops to zero.

A trick, courtesy of Bob Pease: whenever you build a power supply
circuit which carries line voltage or higher, stick an NE-2 neon bulb
and a suitable dropping resistor across the caps, and place the bulb
where it's clearly visible when the case is opened.

If the bulb is lit (at all) the caps have enough voltage in them to
give you a nasty bite.

THEN put a heavy screwdriver with a well insulated handle from ground
to the HV terminal to be sure!

I've heard cautionary notes about this... if you do this prematurely,
the arc can be scary (and dangerous in some cases - "arc flash" burns
can be severe) and I believe it's possible to damage or wreck some
caps as a side effect of a catastrophic high-current discharge.

A heavy grounding wire, with alligator clips, and with a
current-limiting resistor is another possible solution. You want a
low enough impedance to drain away any charge which may come out of
the cap's dielectric "soakage", but high enough to avoid a dangerous
arc flash when you first hook it up.


Keep on hand in the pocket if you need to
adjust anything when it's hot.

That's one of the best single pieces of advice around! Also, be aware
of what sort of grounded metal is around your workbench. Doesn't help
much to keep one hand in your pocket, if you lean your belly against a
grounded metal bench!


HV isn't the only thing that can get you. High current can give you
a nasty surprise. Like the guy replacing some batteries on a golf cart.
He was using a ratchet wrench to tighten the battery clamps and he
ended on the most positive battery terminal. The handle of the wrench
hit the chassis of the golf cart putting it between 36 volts and ground
of some VERY HEAVY DUTY batteries. Ever see a Sears ratchet wrench
glow WHITE HOT? (and melt?)

Haven't seen that myself, but I've heard of people who have had
screwdrivers, etc. literally vaporized under such circumstances.

--
Dave Platt AE6EO
Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

Dave Platt wrote:
In article ,
Ken Scharf wrote:
snip
HV isn't the only thing that can get you. High current can give you
a nasty surprise. Like the guy replacing some batteries on a golf cart.
He was using a ratchet wrench to tighten the battery clamps and he
ended on the most positive battery terminal. The handle of the wrench
hit the chassis of the golf cart putting it between 36 volts and ground
of some VERY HEAVY DUTY batteries. Ever see a Sears ratchet wrench
glow WHITE HOT? (and melt?)


Haven't seen that myself, but I've heard of people who have had
screwdrivers, etc. literally vaporized under such circumstances.

My brother came home from a business trip once with a scar on his wrist
5/8 inches wide and all the way around -- the truck was having
electrical problems & he shorted his metal watch band through the 12V
battery (there was a wrench involved in there somehow, of course).

I felt for him, but I was very glad that _he_ was the one to learn this
first hand, rather than me...

--
-------------------------------------------
Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Dave Platt wrote:
In article ,
Ken Scharf wrote:

HV isn't the only thing that can get you. High current can give you
a nasty surprise. Like the guy replacing some batteries on a golf cart.
He was using a ratchet wrench to tighten the battery clamps and he
ended on the most positive battery terminal. The handle of the wrench
hit the chassis of the golf cart putting it between 36 volts and ground
of some VERY HEAVY DUTY batteries. Ever see a Sears ratchet wrench
glow WHITE HOT? (and melt?)

Haven't seen that myself, but I've heard of people who have had
screwdrivers, etc. literally vaporized under such circumstances.

The canonical "Take-Your-Rings-Off" reminder in our electronics shop
in Japan, back when I was in the AF, was a color image, taken at our
base hospital, of a finger burnt to the bone all the way around: one of
the techs had got his wedding ring between ground and a high-current
low-voltage supply.

--
Mike Andrews W5EGO 5WPM
Extra
Tired old sysadmin working on his code speed