On Oct 27, 2006, at 3:58 PM, craxd wrote:

--- In ham_amplifiers@..., R L Measures <r@...> wrote:

On Oct 27, 2006, at 9:22 AM, david6fl wrote:

I belong to several of these ham discussion groups and also am

amazed

at some of the elemental questions asked by persons with extra

class

call signs.

I have found that few Extras know Ohm's Law.

Some of these are the very same ones who claim to be smarter than
CBr's, and somehow above them! I've heard a lot of name calling by
some Hams towards CBr's,

In my experiences, those who use ad hominems either have something to hide or they are trying to hide from reality.

and the very same ones turn around and ask
questions about things they should know to qualify for the license
they have in their hand. That's called irony in my humble opinion....

I call it being smart enough to ask. At age 15, I built my first amplifier and I asked plenty of questions.

I know some kids talking on walkie-talkies who know ohms law. I also
know a bunch of CBr's who have more knowledge than some of the hams
in mention. Over these very hams is why those CBr's won't upgrade and
get an amateur license.

So a few schlub Hams are keeping them from upgrading? This smells a whole lot like taurine feces, Will.

Now that computers are where they are, and the majority of young
folks use them for about all their long distant communications,
they'll never get them to get a license with the morse code
restrictions.

My sister learned Morse in one evening.

They're not going to learn it when they can set down at
a computer and communicate to anyone in the world. Even if that
restriction is lifted, I don't see them flocking in droves to join
up. Today is not like it was before the PC and cell phones.

...
R L Measures, AG6K, 805.386.3734
r@..., , rlm@..., www.somis.org

Best,

Will





Yahoo! Groups Links

R L Measures, AG6K, 805.386.3734
r@..., , rlm@..., www.somis.org

Pentalab wrote:

--- In ham_amplifiers@..., Tony King - W4ZT <w4zt-
060920@...> wrote:

pentalab wrote:
<snip>

TONY SEZ.... Jim, have you considered sub mounting the tube? Current methods dictate cutting lots of holes around the tube to allow the air to flow. If you sub mount the tube by an inch, mount it on a solid aluminum or, better still, copper plate, you can get LOTS of air up around the seals and up to the anode without a huge wide pattern of holes around the tube. Then a straight chimney will work and you're back to a nice Teflon chimney that's easy to make though a little expensive.
### YC-156 user's do this. Since the YC-156 has a 4.94" OD cooler... but the built in grid ring is a whopping 5.25" OD... obviously a straight up/down teflon chimney won't work in a normal config.

Actually that's not so. The grid ring OD is 5.030" to 5.090" per the data sheet and verified measuring here. The anode is 4.812" to 4.936". That isn't a problem. Stock PTFE tube is available that can be turned easily to fit.

## here's the problem though. You submount the grid flange 1" below the chassis... it's GOTTA be mounted on aluminium/copper standoffs.

That is what some have done but doing it just like I do my GS-35B mounting fixtures <> will eliminate the problem. The standoff could be made from 1/4" flat stock with a pattern of holes. You get the sub mount without giving up the good grid grounding and have great cooling.

Two potential problems. One is.. the grid isn't as

well grnded.

see above

The other is... since you lowered the tube down one

inch.... the stray C from anode to chassis will INCREASE. The chassis will also be getting closer to the lower anode. I haven't measured it.. yet.. but I'm betting the stock 55 pf anode to chassis C will increase by another 10-25 pf, when submounted 1". Maybe not... since this sub mount scheme uses a bigger hole in the chassis to start with 4.94" vs aprx 3-4".

I don't think any appreciable increase in stray will result. the straight chimney will also save lots of horizontal space on the chassis as well as a little vertical space if that was a consideration.

This works the other way too. Reid at Eimac told me fellow's will raise the tube up on a pedestal.. like a hollow piece of aluminium thick wall pipe.... drilled and tapped on both ends... this then gets the anode up AWAY from the chassis.. lowering the anode to grid C.

Nothing you can do external will lower internal anode to grid C. Any external effects caused by lowering the anode by an inch will probably not impact anyone using it below 25 MHz. The only part of the anode cooler getting closer to chassis is the edge. There's not a large flat surface getting closer (except the vertical).

In the submount case, the tube will also have to be inserted from below ! IE: stuff the top of the anode UP through a min 4.94" diam hole in the chassis.

Not in the case of a YC-156 or YC-179. It works just fine inserting it from the top.

Out of interest here. I couldn't initially see why a YC-156 had 36 pf of anode to grid C... which rises to 50-55 pf when bolted to chassis..... while a 3000A7 is only 24 pf... rising to 33 pf..... and a 6000A7 is 24.5 pf... rising to 38 pf. Looking at a 6000A7 closer tells the real story... they have shoved the fins up higher on a 6000A7, right to the top.. compared to a 3000A7.... then on the underside... they sliced the lower fins at a steep upwards rising angle.... to get as much anode away from the chassis... which minimizes stray C. The 6000A7 has a much bigger OD cooler too 6.125" vs 4.94" for a YC-156.

That's true. The physical shape of the bottom of the cooler has everything to do with it but as you said earlier, if the hole is cut out then the closeness is at a diagonal to the bottom of the cooler. The direct impact on the external anode to grid C would have to be measured but I suspect it would be minimal.

Usually, when I cut the holes in the chassis.. instead of using uni-
bit's, greenlee punches... I just cut it out in the shape of a maltese cross.... with my Bosch jig saw. A lot faster,,, and loads of airflow. Use what ever works.

I agree... don't let the absence of a particular tool hold you back! I have to wonder about suspending the tube out there in the middle of the cross. There's a bit inductance gained grid to ground by doing that. Plus there's a significant amount of loss in the conduction of heat away from that flange.

I got the 1/4" thick custom made Teflon chimney from Arnold Howell, of Howell tube sales in Ohio. He had tons of em custom made in Cleveland. They cast em 1st... then machined out the insides to a precise fit. They made em extra Tall... higher then the tube itself.... since the 11m ops all use a fixed vac cap.[for a plate block cap]...and stand it on end vertically.... then they can cool it too.

I use stock PTFE tube from McMaster-Carr and machine it on the lathe as necessary. The stuff just can't be beat!

The chimney is HEAVY... and it's weight holds it to the chassis. Not cheap... about $115.00 new. I'm sure he could [probably allready does] a smaller 4.94" chimney for a YC-156/179 tube. Howell mebtioned to me about submounting the YC-156 yrs ago... then using a straight up/down 1/4" thick teflon chimney.

Unless you really needed the chimney to go high up on the anode, it doesn't take much PTFE tube to make a chimney. Yes, it is a little costly but once done, you never have to worry about it again.

Some guy in W6 land wants me to design an amp around 3 x YC-156's in parallel, GG... low band stuff. I figure with 600w of drive.. it should do 30-36 k out.

Wow... well if one tube isn't enough... you need a BIGGER tube! I can't imagine dealing with the problems of paralleling 3 YC-156's. He needs a 15k or 20k!


<snip>

73, Tony W4ZT

--- In ham_amplifiers@..., Tony King - W4ZT <w4zt-
060920@...> wrote:

pentalab wrote:
<snip>

The trbl with teflon sheeting, etc... is u gotta
anchor it to the chassis. At least with my original Straight

up and down stove pipe chimney..it was 1/4" thick teflon,
and so heavy, it's weight alone held it to the chassis. As
noted b4... it restricted the intake air too much.

TONY SEZ.... Jim, have you considered sub mounting the tube? Current
methods dictate cutting lots of holes around the tube to allow the
air to flow. If you sub mount the tube by an inch, mount it on a
solid aluminum or, better still, copper plate, you can get LOTS of
air up around the seals and up to the anode without a huge wide
pattern of holes around the tube. Then a straight chimney will work
and you're back to a nice Teflon chimney that's easy to make though
a little expensive.

### YC-156 user's do this. Since the YC-156 has a 4.94" OD
cooler... but the built in grid ring is a whopping 5.25" OD...
obviously a straight up/down teflon chimney won't work in a normal
config.

## here's the problem though. You submount the grid flange 1"
below the chassis... it's GOTTA be mounted on aluminium/copper
standoffs. Two potential problems. One is.. the grid isn't as
well grnded. The other is... since you lowered the tube down one
inch.... the stray C from anode to chassis will INCREASE. The
chassis will also be getting closer to the lower anode. I haven't
measured it.. yet.. but I'm betting the stock 55 pf anode to chassis
C will increase by another 10-25 pf, when submounted 1". Maybe
not... since this sub mount scheme uses a bigger hole in the
chassis to start with 4.94" vs aprx 3-4".

This works the other way too. Reid at Eimac told me fellow's
will raise the tube up on a pedestal.. like a hollow piece of
aluminium thick wall pipe.... drilled and tapped on both ends...
this then gets the anode up AWAY from the chassis.. lowering the
anode to grid C.

In the submount case, the tube will also have to be inserted from
below ! IE: stuff the top of the anode UP through a min 4.94"
diam hole in the chassis.

Out of interest here. I couldn't initially see why a YC-156 had
36 pf of anode to grid C... which rises to 50-55 pf when bolted
to chassis..... while a 3000A7 is only 24 pf... rising to 33
pf..... and a 6000A7 is 24.5 pf... rising to 38 pf. Looking at
a 6000A7 closer tells the real story... they have shoved the fins
up higher on a 6000A7, right to the top.. compared to a 3000A7....
then on the underside... they sliced the lower fins at a steep
upwards rising angle.... to get as much anode away from the
chassis... which minimizes stray C. The 6000A7 has a much bigger
OD cooler too 6.125" vs 4.94" for a YC-156.

Usually, when I cut the holes in the chassis.. instead of using uni-
bit's, greenlee punches... I just cut it out in the shape of a
maltese cross.... with my Bosch jig saw. A lot faster,,, and loads
of airflow. Use what ever works.

I got the 1/4" thick custom made Teflon chimney from Arnold
Howell, of Howell tube sales in Ohio. He had tons of em custom
made in Cleveland. They cast em 1st... then machined out the
insides to a precise fit. They made em extra Tall... higher then
the tube itself.... since the 11m ops all use a fixed vac cap.[for
a plate block cap]...and stand it on end vertically.... then they
can cool it too.

The chimney is HEAVY... and it's weight holds it to the chassis.
Not cheap... about $115.00 new. I'm sure he could [probably
allready does] a smaller 4.94" chimney for a YC-156/179
tube. Howell mebtioned to me about submounting the YC-156 yrs
ago... then using a straight up/down 1/4" thick teflon chimney.
Some guy in W6 land wants me to design an amp around 3 x YC-156's
in parallel, GG... low band stuff. I figure with 600w of
drive.. it should do 30-36 k out.

later... Jim VE7RF

<snip>

73, Tony W4ZT

--- In ham_amplifiers@..., R L Measures <r@...> wrote:

On Oct 27, 2006, at 9:22 AM, david6fl wrote:

I belong to several of these ham discussion groups and also am

amazed

at some of the elemental questions asked by persons with extra

class

call signs.

I have found that few Extras know Ohm's Law.

Some of these are the very same ones who claim to be smarter than
CBr's, and somehow above them! I've heard a lot of name calling by
some Hams towards CBr's, and the very same ones turn around and ask
questions about things they should know to qualify for the license
they have in their hand. That's called irony in my humble opinion....

I know some kids talking on walkie-talkies who know ohms law. I also
know a bunch of CBr's who have more knowledge than some of the hams
in mention. Over these very hams is why those CBr's won't upgrade and
get an amateur license.

Now that computers are where they are, and the majority of young
folks use them for about all their long distant communications,
they'll never get them to get a license with the morse code
restrictions. They're not going to learn it when they can set down at
a computer and communicate to anyone in the world. Even if that
restriction is lifted, I don't see them flocking in droves to join
up. Today is not like it was before the PC and cell phones.

...
R L Measures, AG6K, 805.386.3734
r@..., , rlm@..., www.somis.org

Best,

Will

On Oct 27, 2006, at 3:26 PM, pentalab wrote:

--- In ham_amplifiers@..., R L Measures <r@...> wrote:

On Oct 27, 2006, at 9:22 AM, david6fl wrote:

I belong to several of these ham discussion groups and also am

amazed at some of the elemental questions asked by persons with
extra class call signs.

Rich Sez... I have found that few Extras know Ohm's Law.

### I concur. Ohm's law, and it's derivatives [ohms 'wheel']

should be plastered on page 1 of all these books.

### The simple formulae for XC/XL/C/L are either not in most
books, or buried, or non existent... or strewn all over the map.

### or they give answers in farads + henry's + cps, etc.

### it's an easy tweak to the initial formula to fix that

eg; XC = 1,000,000 / 2 x pi x F x C Use mhz and pf
inserted into the formula... and it all comes out just right.....
in ohms. If u use the normal 1 / 2 x pi x f x c.... u gotta
insert freq as hz and C as farads. Why mess with
14,350,000.00 hz... when u can just use 14.35 in the 1st place...
[with the tweaked formula]

### Rich,,, ur PI spread sheet is like that... answers come out in
henry's and farads. Too easy to make an error..

What me worry?

when C1 comes
out to .00000000036. Then it's left to the end user to figure
out whether it's 3.6 pf 36 pf 360 pf 3600 pf....esp at 2
am !

### once one knows what XC is... then substitute XC in ohms law
to derive everything else... like VA power, v drop, current , etc.
THEN... u can size stuff up easier.

### If u want to know say... how much RF current flows through the
main tank coil..... and if u know the value of the load cap.. and
the power output.... it's easy. Calculate the XC of the load cap
at the given freq... then calculate the current throught it.. easy,
since you what the power output is... u can easily calculate the
rms/peak V across the cap [same as the ant, load cap is in parallel
with the 50 ohm coax]. Calculate the RF current going up the 50
ohm coax. Current coming outa the main tank coil is equal to
the square root of ..... the square of the load cap current + the
square of the antenna current.

Which comes out pretty close to just DC plate current x Loaded
Q....

Correctomundo

...

R L Measures, AG6K, 805.386.3734
r@..., , rlm@..., www.somis.org

--- In ham_amplifiers@..., R L Measures <r@...> wrote:

On Oct 27, 2006, at 9:22 AM, david6fl wrote:

I belong to several of these ham discussion groups and also am

amazed at some of the elemental questions asked by persons with
extra class call signs.

Rich Sez... I have found that few Extras know Ohm's Law.

### I concur. Ohm's law, and it's derivatives [ohms 'wheel']

should be plastered on page 1 of all these books.

### The simple formulae for XC/XL/C/L are either not in most
books, or buried, or non existent... or strewn all over the map.

### or they give answers in farads + henry's + cps, etc.

### it's an easy tweak to the initial formula to fix that

eg; XC = 1,000,000 / 2 x pi x F x C Use mhz and pf
inserted into the formula... and it all comes out just right.....
in ohms. If u use the normal 1 / 2 x pi x f x c.... u gotta
insert freq as hz and C as farads. Why mess with
14,350,000.00 hz... when u can just use 14.35 in the 1st place...
[with the tweaked formula]

### Rich,,, ur PI spread sheet is like that... answers come out in
henry's and farads. Too easy to make an error.. when C1 comes
out to .00000000036. Then it's left to the end user to figure
out whether it's 3.6 pf 36 pf 360 pf 3600 pf....esp at 2
am !

### once one knows what XC is... then substitute XC in ohms law
to derive everything else... like VA power, v drop, current , etc.
THEN... u can size stuff up easier.

### If u want to know say... how much RF current flows through the
main tank coil..... and if u know the value of the load cap.. and
the power output.... it's easy. Calculate the XC of the load cap
at the given freq... then calculate the current throught it.. easy,
since you what the power output is... u can easily calculate the
rms/peak V across the cap [same as the ant, load cap is in parallel
with the 50 ohm coax]. Calculate the RF current going up the 50
ohm coax. Current coming outa the main tank coil is equal to
the square root of ..... the square of the load cap current + the
square of the antenna current.

Which comes out pretty close to just DC plate current x Loaded
Q.... this method described above comes out dead on.

Too bad you don't see this stuff in any ARRL hand book... heck it's
not even in Orr's books. No wonder fellow's are confused. Having
peak/rms currents and voltages across C1 L1 C2.. plate block caps
[esp high bands] plate RFC RF current, bypass caps at base of
plate choke, etc, etc.. would be the ultimate addition to any of the
current PI- spread sheets.[on a band per band basis] That plus,
you just have to be able to factor in stray L between the anode
and the input of the PI.... since usually a tiny bit of L is needed
b4 the main pi-net... so u don't have to run a sky high Q on the
higher bands......esp with tubes like YC-156/179's... that already
have 55 pf of stray anode to grid C. Sky high loaded Q means
it's gonna be narrow banded and critical tuning.. + cooked
bandswitch contacts, coils, etc. It's easy to transform the plate
load Z WAY down.... so the Pi net has something it can work
with... with a more normal Q.

later... Jim VE7RF

...
R L Measures, AG6K, 805.386.3734
r@..., , rlm@..., www.somis.org

On Oct 27, 2006, at 9:22 AM, david6fl wrote:

I belong to several of these ham discussion groups and also am amazed
at some of the elemental questions asked by persons with extra class
call signs.

I have found that few Extras know Ohm's Law.

...
R L Measures, AG6K, 805.386.3734
r@..., , rlm@..., www.somis.org

Cq ww ssb contest this weekend. You will be hearing some BIG
tubes this weekend... all bands.

Good... cuz I helped design several of em. Hope they have fun....
more power to em ....[no pun intended, lol]


"when the pole pig begins to bubble, the contester knows he's now in
trbl "

" turn the variac to the right... and work the Ja's all through the
night"

outa here... have fun

later... Jim VE7RF

I belong to several of these ham discussion groups and also am amazed
at some of the elemental questions asked by persons with extra class
call signs. I am not an electronics engineer or anything like it but
I have built receivers, transmitters, amplifiers, and all sorts of
accessory items for them.

I have one of the old advanced class licenses and was never motivated
enough by the small bit of extra band width and bragging rights to
put in the effort to get my code up to 20 wpm.

At no time did I ever consider purchasing a linear amp, kit or
otherwise. When I wanted a new amp, I built it.

David
KC2JD

--- In ham_amplifiers@..., "Mike&#92;(W5UC&#92;) & Kathy&#92;(K5MWH&#92;)"
<w5uc@...> wrote:

Bill, how sad, but true. I am amazed at the number of new licensees

in the

local club, some Extra Class, who don't have the foggiest idea how to
calculate the length of a dipole, or how to put it up.

There are a couple over here in Europe. So does that mean European hams are brighter! :-)

Linear Amp UK sell their Ranger 811 HF amp as a kit and also make available parts like transformers, capacitors etc



And in Denmark Dan's amps have parts available for various models and say they will be selling a full kit soon



73 Paul G4DCV

There are a couple over here in Europe. So does that mean European hams are brighter! :-)

Linear Amp UK sell their 4 x 811 amp as a kit

And in Denmark Dan's amps

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ORIGINAL MESSAGE:

On Wed, 25 Oct 2006 14:57:52 -0000, "ad4hk2004" <ad4hk2004@...>
wrote:

The price of metal
stampings and machined parts that have been drilled and tapped,
cleaned, powder coated and baked, then shipped to your plant, will
take your breath away...

------------ REPLY FOLLOWS ------------

Perhaps it could be done with blank metal pieces and a paper template
for the builder to drill and finish himself?

Your other comments about "key down for four hours" etc, are well
taken. Everything considered, it's not likely to happen. If it were
cost-effective, Heathkit would still be in business.

The other part of the equation is that hams who are real technicians
are becoming a rare species. I hate the phrase "appliance operator"
but it often applies, I'm sorry to say. Not to this group, though. :-)

Bill, W6WRT

On Oct 27, 2006, at 12:22 AM, pentalab wrote:

--- In ham_amplifiers@..., R L Measures <r@...> wrote:

On Oct 26, 2006, at 2:11 PM, Phil Clements wrote:

I received a lot of interesting posts when I asked about

repairing

a grid
bypass choke fire on a customer's SB-220.

Another fix was to replace the 200 pf bypass caps with at least

500 pf

units, and replace the RF chokes with fusing resistors.

RICH SEZ... In my experiences, a suitable glitch-R in the HV+ helps

prevent grid- filament shorts.

### agreed... when stuff "goes nuts"... the glitch will LIMIT
current..... precede the glitch with a HV fuse... and that combo is
excellent.

? What failure does the HV fuse protect against with thoriated
tungsten filament tubes?

Come glitch time.. it's always limiting , followed
by HV fuse opening....saves all sorts of destruction... whether
cuzed by parasitics.. or anything else.

...
The question of the day is why Henry chose a more expensive
approach than
any of their competitors?

### I wondered about that scheme too........ most bizzare
contraption ever devised.... and those amps work just great with the
grids directly grnded to the chassis.. and a grid fuse installed..
plus glich/hv fuse etc. I'm sure Rube Goldberg and Muncy both
worked for Henry Radio at one time.

RICH SEZ.. A friend went the Henry booth at a Hamvention and

asked one of the Henry engineers why none of the Henry 3-500Z
amplifiers currently had 160m coverage. The reply: 1.8MHz is
below the 3-500Z's low- frequency cutoff.

### LOL. Joke right ??

? No

Early Henry amplifiers had a problem welding the contacts of

the power contactor that was used to switch them on and off.
Instead of doing the obvious -- adding a step-start relay and 2
step-start resistors, Henry's solution was to install an uncheap
humungous power contactor with mercury-wetted contacts.

### You never install 2 x step start resistors..... it's total loop
resistance we are concerned with here. Just install one step
start resistor.. in one leg of the 240 line.

? One step-start R will not work with amplifiers that are made for
dual 120v/240v operation.

I use a 25 ohm
unit... consisting of a pair of 50 ohm resistor's in parallel [50
w /100w each]. The paralleled approach offers redundancy...if one
ever opened... still got the 2nd one.. albeit 50 ohms. All thta's
neede is a SPST-DM contactor or SPST relay to sort out the one
step start resistor. Stick one per leg,, and you then need a
DPST relay/contactor to short it out.

? Correct, and it will step-start on either 120v or 240v.

### Mercury wetted contacts is another waste of time.

? ... and money.

Loads of
good contactor's out there. A standard contactor is just 2 sets
of contacts.. in series... PER POLE, so u end up with no arcing
when trying to open a load off. [u split the arc into two
simultaneous arcs = zero arc].

? I disagree. Inductive loads can produce 25x the operating
potential when current stops.

They are called DPDT-DM [double
make]. Regular contactor's have the distinct advantage that
their contacts are all easily field replaceable. I clean new ones
up... slop some "cool amp" silver plating compound on em... and
zero ohms guaranteed everytime.

? Zero-ohms without liquid helium cooling?

You can slop a tiny layer
of "conducto lube" [pure silver powder, suspended in grease, made
for moving/sliding contacts] on em as well..... results in 110 %
success every time.... last a long time. Too many stock
contacts don't quite result in zero ohms when pushing on em with
ur fingers.. really hard.

### My conclusion is Henty doesn't "get it" with some aspects of
their stuff. I have their 10 kw LP filter.... compact,
superbly designed... then they can't build a HV supply right.
Their resonant choke scheme looks good on paper.. then Henry ends
up using one bad HV xfmr maker after another after another. IMO...
dump the resonant choke scheme alltogether, install a hypersil C
core, and a heavy duty FWB [1 kv- 6A -400 A surge diodes are dirt
cheap] , and a large C input filter.... and step start. If ur
gonna stick a ton of extra weight in there... add it to the plate
xfmr... not a choke.

I would love to hear the reasoning and experiences
when they built up the prototype of this amp.

### They probably all dragged out their 1934 engineering books.

The direct-grounding camp all reports no problems since their

mod. and swearby that solution.

### Yeah, I swear by it.... esp after 40 e-mails from other SB-
220/221/TL-922 owners, who also swear by it. It's worth it
anyway... guranteed 22-25 watts LESS drive required. I have yet
to hear from any of those guys about parasitic problems either.
The guys with the TL-922's all said.. after directly grnding the
grids to the chassis.... they could all remove the after market
nichrome suppressor's... and re-install the stock kenwood
suppressor's..... rock stable.

RICH SEZ....The AL-82 and uses directly-grounded 3-500Z grid pins

and it has a well-deserved reputation for arcing open contacts on
its bandswitch.

### That's an apples and concrete comparison Rich. The AL-82 [2
x 3-500Z} is called the "firecracker" by the east coast crowd. The
AL-82 is an abortion..... along with it's little bastard child.. the
AL-80B. Both of em like to spit out flames... new right out of the
box..... and that's with just one good short coax.. from amp to
dummy load.... and using PTT... and keeping the loading heavy. The
layout is screwed up in both those amps. Notice the extra
bandswitch wafer's, and extra caps switched in across the bandswitch
itself..... it appears they have an internal resonance bandswitch
problem...esp on 17m.

The toasted bandswitch in the jpg has damage mostly where the 10m and 15m contacts used to be.

### These guys just don't get it. You gotta use correct size
components to start with...

The bandswitch has a 5000v BD and the max potential during operation
is c. 3000v.

and NO wire from any bandswitch
contacts..... just wide, silver plated strap

Round conductors exhibit uniform RF current distribution, flat
conductors don't.

...

The other three solutions speak for themselves, as there
must be thousands of 3-500Z's operating in the field with long

track records. The problems seem to increase when replacing Eimac
tubes with knock-offs.

RICH SEZ... Most of the grid-filament shorted tubes that I have high-

potted were Eimacs.

### All eimac 3=500Z's have a MU= 130 Knock off's are all
MU=200.

Then why do RF Parts 3-500s have the same ZSAC as Eimacs in a SB-220
or TL-922 while Amperex 3-500s exhibit a lower ZSAC?

...end

R L Measures, AG6K, 805.386.3734
r@..., , rlm@..., www.somis.org

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pentalab wrote:

pentalab wrote:
<snip>

### I'm into high level experimentation... up to a point. Between soft x rays, heat, globs of RF, 8000Vdc, etc.... Teflon seemed like a sure fire method/zero brainer. [u know it's gonna work ]

There's nothing better!

<snip>

### agreed.... but I didn't want to make a major project out of a chimney. The trbl with teflon sheeting, etc... is u gotta anchor it to the chassis. At least with my original Straight up and down stove pipe chimney..it was 1/4" thick teflon, and so heavy, it's weight alone held it to the chassis. As noted b4... it restricted the intake air too much.

Jim, have you considered sub mounting the tube? Current methods dictate cutting lots of holes around the tube to allow the air to flow. If you sub mount the tube by an inch, mount it on a solid aluminum or, better still, copper plate, you can get LOTS of air up around the seals and up to the anode without a huge wide pattern of holes around the tube. Then a straight chimney will work and you're back to a nice Teflon chimney that's easy to make though a little expensive.

<snip>

73, Tony W4ZT

--- In ham_amplifiers@..., R L Measures <r@...> wrote:

On Oct 26, 2006, at 2:11 PM, Phil Clements wrote:

I received a lot of interesting posts when I asked about

repairing

a grid
bypass choke fire on a customer's SB-220.

Another fix was to replace the 200 pf bypass caps with at least

500 pf

units, and replace the RF chokes with fusing resistors.

RICH SEZ... In my experiences, a suitable glitch-R in the HV+ helps

prevent grid- filament shorts.

### agreed... when stuff "goes nuts"... the glitch will LIMIT
current..... precede the glitch with a HV fuse... and that combo is
excellent. Come glitch time.. it's always limiting , followed
by HV fuse opening....saves all sorts of destruction... whehter
cuzed by parasitics.. or anything else.

Absolutely nobody suggested returning the circuit to original
factory specs.

## The original factory spec just copied the L4B that came out in 1969
and the earlier L4 [1964] verbatim... they were all wrong... still
are.

On the far-end of the spectrum from direct-grounding of the

grids

has to be
the Henry 2K-4. No RF chokes are utilized, but there are 18-

.003

mfd bypass
caps, 12- 10 ohm resistors, and a 250 ohm grid ma adjust
potentiometer, all
hanging from grid pins to chassis! Grid pins (pin #4) of each

tube are

strapped together. Pins 2 and 3 on each tube are strapped

together,

but not
strapped tube-to-tube. Also, Henry chose to use 2- 150 ohm
resistors in
parallel with the coil on the parasitic suppressors.

The question of the day is why Henry chose a more expensive
approach than
any of their competitors?

### I wondered about that scheme too........ most bizzare
contraption ever devised.... and those amps work just great with the
grids directly grnded to the chassis.. and a grid fuse installed..
plus glich/hv fuse etc. I'm sure Rube Goldberg and Muncy both
worked for Henry Radio at one time.

RICH SEZ.. A friend went the Henry booth at a Hamvention and

asked one of the Henry engineers why none of the Henry 3-500Z
amplifiers currently had 160m coverage. The reply: 1.8MHz is
below the 3-500Z's low- frequency cutoff.

### LOL. Joke right ??

Early Henry amplifiers had a problem welding the contacts of

the power contactor that was used to switch them on and off.
Instead of doing the obvious -- adding a step-start relay and 2
step-start resistors, Henry's solution was to install an uncheap
humungous power contactor with mercury-wetted contacts.

### You never install 2 x step start resistors..... it's total loop
resistance we are concerned with here. Just install one step
start resistor.. in one leg of the 240 line. I use a 25 ohm
unit... consisting of a pair of 50 ohm resistor's in parallel [50
w /100w each]. The paralleled approach offers redundancy...if one
ever opened... still got the 2nd one.. albeit 50 ohms. All thta's
neede is a SPST-DM contactor or SPST relay to sort out the one
step start resistor. Stick one per leg,, and you then need a
DPST relay/contactor to short it out.

### Mercury wetted contacts is another waste of time. Loads of
good contactor's out there. A standard contactor is just 2 sets
of contacts.. in series... PER POLE, so u end up with no arcing
when trying to open a load off. [u split the arc into two
simultaneous arcs = zero arc]. They are called DPDT-DM [double
make]. Regular contactor's have the distinct advantage that
their contacts are all easily field replaceable. I clean new ones
up... slop some "cool amp" silver plating compound on em... and
zero ohms guaranteed everytime. You can slop a tiny layer
of "conducto lube" [pure silver powder, suspended in grease, made
for moving/sliding contacts] on em as well..... results in 110 %
success every time.... last a long time. Too many stock
contacts don't quite result in zero ohms when pushing on em with
ur fingers.. really hard.

### My conclusion is Henty doesn't "get it" with some aspects of
their stuff. I have their 10 kw LP filter.... compact,
superbly designed... then they can't build a HV supply right.
Their resonant choke scheme looks good on paper.. then Henry ends
up using one bad HV xfmr maker after another after another. IMO...
dump the resonant choke scheme alltogether, install a hypersil C
core, and a heavy duty FWB [1 kv- 6A -400 A surge diodes are dirt
cheap] , and a large C input filter.... and step start. If ur
gonna stick a ton of extra weight in there... add it to the plate
xfmr... not a choke.

I would love to hear the reasoning and experiences
when they built up the prototype of this amp.

### They probably all dragged out their 1934 engineering books.

The direct-grounding camp all reports no problems since their

mod. and swearby that solution.

### Yeah, I swear by it.... esp after 40 e-mails from other SB-
220/221/TL-922 owners, who also swear by it. It's worth it
anyway... guranteed 22-25 watts LESS drive required. I have yet
to hear from any of those guys about parasitic problems either.
The guys with the TL-922's all said.. after directly grnding the
grids to the chassis.... they could all remove the after market
nichrome suppressor's... and re-install the stock kenwood
suppressor's..... rock stable.

RICH SEZ....The AL-82 and uses directly-grounded 3-500Z grid pins

and it has a well-deserved reputation for arcing open contacts on
its bandswitch.

### That's an apples and concrete comparison Rich. The AL-82 [2
x 3-500Z} is called the "firecracker" by the east coast crowd. The
AL-82 is an abortion..... along with it's little bastard child.. the
AL-80B. Both of em like to spit out flames... new right out of the
box..... and that's with just one good short coax.. from amp to
dummy load.... and using PTT... and keeping the loading heavy. The
layout is screwed up in both those amps. Notice the extra
bandswitch wafer's, and extra caps switched in across the bandswitch
itself..... it appears they have an internal resonance bandswitch
problem...esp on 17m.

### These guys just don't get it. You gotta use correct size
components to start with... and NO wire from any bandswitch
contacts..... just wide, silver plated strap for ALL
interconnections. I'd dump the PI-L nonsense, sky high loaded Q
circuits on high bands..... torroids on either the main or L-2
coil.... and other bizzare concepts like building a PI designed
to transform the tube's plate load Z.. down to 200 ohms... then using
a broadband torroid to transform the 200 ohms.. down to 50 ohms.
Diito with using PC boards to terminate tank coils on. RG-174
is to be avoided like the plague.

### The sad part is... then people will ask u to "fix" or re-
design "it".... and "It" is an ill conceived amp.... in a shoe
box.

The other three solutions speak for themselves, as there
must be thousands of 3-500Z's operating in the field with long

track records. The problems seem to increase when replacing Eimac
tubes with knock-offs.

RICH SEZ... Most of the grid-filament shorted tubes that I have high-

potted were Eimacs.

### All eimac 3=500Z's havee a MU= 130 Knock off's are all
MU=200.

It is obvious to me that some kind of grid fusing should be
included in any
modification one chooses.

RICH SEZ Indeed, Phil, unless one has a free supply of new 3-500Zs.

### agreed.... and this will set u back the cost of one high speed
3agc fuse...and one rear panel 3agc fuse holder..... what's that
come out to .... about $1.50 tops....... Ameritron could no
doubt get em for 20 cents... buying 100 K at a time.... then use
em in all their various amps..... cheap bastards..... ditto with
their RG-174 sub minature coax used in the tuned input to cathode.

I just wanted to pass along my experiences FWIW. Mods seem to be

in

order; the choice is up to you!

### The choice is.... stock, it's an accident waiting to happen...
so u either mod it now...... OR blow it up... THEN mod it.

Later.... Jim VE7RF

(((73)))
Phil Clements, K5PC






Yahoo! Groups Links

R L Measures, AG6K, 805.386.3734
r@..., , rlm@..., www.somis.org

--- In ham_amplifiers@..., "Mike&#92;(W5UC&#92;) &
Kathy&#92;(K5MWH&#92;)" <w5uc@...> wrote:

Good Morning Noel & All:



I have started construction on a pair of GI-7b's for 6 meters, but

6 mtrs

cooled and 160 Mtrs got ready to come on for the winter. You can

see my

progress, or lack thereof on my web page.

>
73,

Mike, W5UC

#### then click on..."stuff" I tried the pi net for my tuned
inputs.... and it's slick.... since it does ALL bands at once. By
tweaking the Q in tiny increments... it spat out virtually
identical results to what we are using on both the 3000 A7 amp..
and the 6000A7 amp. Now here's the kicker..... the tube's input
Z may be a little lower than 50 ohms in my case.... and when
feeding with 50 ohm coax.... u will end up with a conjugate
match... so allow leeway [esp on 160m].. esp on the C2 cap closest
to cathode.

### another caveat with tuned inputs is... I ran 50 ohm coax
from the output of my vraiable tuned inputs... through a bird.. then
into dummy load..... could be tweaked dead flat on all bands. Trbl
was.... with exactly 200 w going in [had another bird on input
side], power out of tuned input , on low bands was around 195 w.
On 17-15... dropped to 160w ! Had to increase the L very
slightly.. reduce the C1 C2 caps a tiny bit.... then power out of
tuned inputs shot up to 193 watts.... and all is well. Point
is... don't run the Q too high.. run it high enough [on high bands
only] so power out of the tuned input on test jig just drops off...
then reduce the Q slightly [more L, less C1 + C2]

## Once output bird is removed.. and coax routed to tube's
cathode, etc.... and in operation on the air/dummy load... C1 + C2
caps are very close to the test set up..... just a little tweaking
on em resulted in ZERO watts reflected power... MAX grid current on
tube....and xcvr/ipa happy.

## Have not tried the pi spread sheets for big pi output... yet.
Dunno whether they factor in the stray L between anode and PI or
not.. as this has a huge effect... since any stray L b4 the PI
will drop/transform the plate load Z.. like a rock... which is
fine... but the PI has to be designed around a lower plate load Z.

all in all... superb sheet. Gotta spend more time with it. It
would be nice to have something that calculates the expected
peak/rms currents and rf voltages across all the components....
including the plate block cap, anode to chassis path, C1 C2...
and coil... + ant current. Then it makes it easier to size
stuff.

later.... Jim VE7RF