It was done because the TR-4/3 went mobile and the filaments ran off the
battery.

That's why I build all my antennas out of steel.

My 80 meter beam weighs 62,000 pounds.

BOB DD

pentalab escribi:

Perhaps there were variations due to availability of certain tubes??; I have two schematics and in both figures the use of 6JB6's in parallel (3.6A intended heater current), but with a couple minor changes in other tubes; these parallel 6JB6 are in series with a string of many tubes which 6V filament currents added is also 3.6A, and the whole series arrangement fed with 12.6VAC.
When the owner put the Penta's with the added heater current, voltage drop was wrong, a lot more than 6.3V at the miniature (7 and 9 pin) tubes, and a lot less than 6.3V at the "6JB6".
Now I figure why (also why) Drake recommended to use only Sylvania tubes.

Best regards
Guillermo - LU8EYW.

On Dec 19, 2006, at 7:57 AM, n6jp wrote:

- due to its abundance of feedback C, i f I had an amp whose
3cx1200A7 was bad, I would go to the trouble of converting it to a
3cx1200Z7.

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

What are the typical changes that need to be addressed in switching
from a 'A7' tube to a 'Z7' tube?

Less filament V., more filament A., different socket. Uncheap.

Jer

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

Thanks. The 3cx1200D7 has less feedback C that the A7 version.

On Dec 19, 2006, at 1:27 PM, ad4hk2004 wrote:

Sorry, I need to be more specific... 3CX1200D7 (YU121)

denny

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

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

On Dec 19, 2006, at 3:25 PM, pentalab wrote:

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

On Dec 19, 2006, at 5:08 AM, ad4hk2004 wrote:

It appears I am in need of a new/rebuilt 3CX1200... I had a long

talk

with Eimac yesterday and after going over the symptoms on my

Henry he

has me convinced that the tube has changed its input impedence

RICH SEZ....Not very likely. What is the Q of the input tuned Pi-

network?

#### The 3 k ultra doesn't have a PI net tuned input... it uses
broad banded xfmrs back to back, and relays.

Does it use g-g config?

not the
amp circuitry - especially since every component has been

inspected,

metered, jiggled, and sniffed, and nothing amiss is found... We

have

spent considerable time and effort using VOM, LC meter, MK-I

eyeballs,

etc. to prove the mechanical and electrical charateristics of all
relays, RF cables, caps, inductors, resistors, transformers,

diodes,

and on, and on... We found that the Henry manual is not 100%

accurate,

but the errors are easily spotted and not significant if you
understand basic electronics... <such as showing an indirectly

heated

cathode on a 3CX1200>

chortle

The crucial test suggested by Eimac was to take the filament

voltage

above it's nominal and recheck the input impedence and power

out...

We raised the voltage to 6.8 volts and the input swr to the

cathode

promptly dropped from 3.8 to 1.9 ... The tube now puts out 1100

watts

with 48 watts in and the grid current is right at the 200 mils
limit...

### well rich.. I guess eimac is right... since his input swr
dropped like a rock.... still not flat..... but I don't hink any of
the 3k/8 k ultra's were ever dead flat.... with that broadbanded
input.

There is no such thing as a broadbanded input for g-g. Did Henry Radio get out of the amplifier business?


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

--- In ham_amplifiers@..., GGLL <nagato@...> wrote:

Hello, I want to ask about something that happened this week

with the output

tubes in a Drake TR-4 I was committed to repair. It has three 6JB6

in parallel

to achieve 200..220 watts out at 80, less at the upper bands. To

my surprise,

the tubes (Penta brand) appear to be 6V but to take a lot more

heater current

than the data sheet specified 1.2A.
Have you had any experience with a similar thing?.

### The Drake TR-4 and older TR-3 all used 3 x 12JB6's... with
all the 12.6 v fils in parallel. The drake T4X/C used a pair
of 6JB6's [6.3 v fils] with the two fils in series. This was
done so the mating AC-3/4 power supply would run either the TR-
3/4 xcvr.. or the T4X/C TX.

Later....... Jim VE7RF

Best regards
Guillermo - LU8EYW.

--- In ham_amplifiers@..., "craxd" <craxd@...> wrote:

The way they're building most amps these days is to use a clam

shell

type cabinet made of aluminum or like to C's placed together at 90
degree angles. The actual tube chassis is a box made with aluminum
just large enough to fit the tube sockets in the top of it. This

then

is placed inside, generally at the rear of the cabinet. I would
rather have the top of this box-tube chassis made with either

copper

or steel where I can solder the bypass caps directly to it or any
other ground connection. I've used steel in a lot of amps, and
personally I think it takes a bad rap over other probelms that are
not its fault. Of course copper would be the best, however there's
not enough steel here to hurt anything, and the rest of the

cabinet

is aluminum anyhow. Aluminum is supposed to be better at

shielding,

but I'm not convinced that is is that much better than steel.

#### steel...esp Stainless steel.. doesn't handle RF worth a
damn. Don't believe me.... tey making a hairpin match from
stainless steel wire..... right at the dead center point it will
turn BLACK every time [ electrical neutral point, zero V... current
is max.] If u grnd the mid point to the boom.... u now have
a "beta match"... ala hi-hain ants.

### Notive how JA6TAY uses a large copper plate arounf the tube
socket on his big metal tube amps..... then it's aluminium. There
is one helluva lot of Rf current between the anode and chassis
grnded grid on a GG triode amp.

### I used steel chassis's on some hb 6146 B TX's back in the
early 70's... a real pain to cut, and drill, and work with.
Pland jane sheet metal has a tendency to rust too. I stopped
using steel for fronta and rear panels as well. Steel is
great for removable sides of rack cabinets... and the actual rack
itself... that's it.

Later... Jim VE7RF

Actually, copper weighs a little more than steel.

Copper: 0.295 pounds In^3
Aluminum: 0.098 pounds In^3
Steel: 0.283 pounds In^3

Copper also has the lowest yield strength of all three with steel
being the highest.

Best,

Will

--- In ham_amplifiers@..., "pentalab" <jim.thomson@...>
wrote:

--- In ham_amplifiers@..., Bill Turner <dezrat@>
wrote:

ORIGINAL MESSAGE:

On Sun, 17 Dec 2006 21:02:58 -0500, "Harold Mandel" <ka1xo@>
wrote:

The tighter the stuff is squeezed together (like in copper) the

easier it is

for the wiggling to be picked up

by neighboring "stuff." This then translates to copper being a

better

conductor of heat than aluminum.

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

In light of your statements above, I have two questions:

1. Why is diamond, which is less dense than copper, a better heat
conductor?

2. Why is lead, which is more dense than copper, a worse heat
conductor.

### as I mentioned b4... steel weighs aprx the same as copper...
and doesn't conduct heat worth a damn .2 to 1 ratio for steel
to copper [all the heat trnasfer tables use copper as the
reference = 1] AL is only .57 to 1 Lead is heavy as
hell... and doesn't conduct heat worth banana's.

Jim VE7RF

Bill, W6WRT

开云体育

--- In ham_amplifiers@..., Bill Turner <dezrat@...>
wrote:

ORIGINAL MESSAGE:

On Sun, 17 Dec 2006 21:02:58 -0500, "Harold Mandel" <ka1xo@...>
wrote:

The tighter the stuff is squeezed together (like in copper) the

easier it is

for the wiggling to be picked up

by neighboring "stuff." This then translates to copper being a

better

conductor of heat than aluminum.

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

In light of your statements above, I have two questions:

1. Why is diamond, which is less dense than copper, a better heat
conductor?

2. Why is lead, which is more dense than copper, a worse heat
conductor.

### as I mentioned b4... steel weighs aprx the same as copper...
and doesn't conduct heat worth a damn .2 to 1 ratio for steel
to copper [all the heat trnasfer tables use copper as the
reference = 1] AL is only .57 to 1 Lead is heavy as
hell... and doesn't conduct heat worth banana's.

Jim VE7RF

Bill, W6WRT

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

On Dec 19, 2006, at 5:08 AM, ad4hk2004 wrote:

It appears I am in need of a new/rebuilt 3CX1200... I had a long

talk

with Eimac yesterday and after going over the symptoms on my

Henry he

has me convinced that the tube has changed its input impedence

RICH SEZ....Not very likely. What is the Q of the input tuned Pi-

network?

#### The 3 k ultra doesn't have a PI net tuned input... it uses
broad banded xfmrs back to back, and relays.

not the
amp circuitry - especially since every component has been

inspected,

metered, jiggled, and sniffed, and nothing amiss is found... We

have

spent considerable time and effort using VOM, LC meter, MK-I

eyeballs,

etc. to prove the mechanical and electrical charateristics of all
relays, RF cables, caps, inductors, resistors, transformers,

diodes,

and on, and on... We found that the Henry manual is not 100%

accurate,

but the errors are easily spotted and not significant if you
understand basic electronics... <such as showing an indirectly

heated

cathode on a 3CX1200>

chortle

The crucial test suggested by Eimac was to take the filament

voltage

above it's nominal and recheck the input impedence and power

out...

We raised the voltage to 6.8 volts and the input swr to the

cathode

promptly dropped from 3.8 to 1.9 ... The tube now puts out 1100

watts

with 48 watts in and the grid current is right at the 200 mils
limit...

### well rich.. I guess eimac is right... since his input swr
dropped like a rock.... still not flat..... but I don't hink any of
the 3k/8 k ultra's were ever dead flat.... with that broadbanded
input.


later... Jim VE7RF

Guillermo,

Those tubes are rebrands so it's untelling who actually made them. If
it was GE years ago, look to see if there is a series of little dots
etched into the glass where the tube number is at. If the dots are
there, it's a GE tube. If not, they could be Sylvania, RCA, etc.

The thing is, several tube manufacturers made tubes with the same
number. However, between brands, some could have differences in
current when voltage is applied. One tube could have a lower heater
current than another in these.

Another thing to look for is that they took one tube number and named
it another because the innards were wired the same. That's kind of
unscrupulous to do, but has been done. That's the same as replacing a
6JS6C with a 6KD6.

If Penta is having new sweep tubes made in China, and having them re-
branded, I'd sure like to know about it and what they can get.
However, I sure won't pay $50 a piece for any sweep tube. I know for
a fact they don't cost that much from China as I had some 6LF6's
quoted to me once. By buying in the 1000 lots, they were going to
cost about $8.00 each from a prominent Chinese manufacturer. At the
most was at $15 each.

Best,

Will


--- In ham_amplifiers@..., GGLL <nagato@...> wrote:

Hello, I want to ask about something that happened this week

with the output

tubes in a Drake TR-4 I was committed to repair. It has three 6JB6

in parallel

to achieve 200..220 watts out at 80, less at the upper bands. To my

surprise,

the tubes (Penta brand) appear to be 6V but to take a lot more

heater current

than the data sheet specified 1.2A.
Have you had any experience with a similar thing?.

Best regards
Guillermo - LU8EYW.

Hello, I want to ask about something that happened this week with the output tubes in a Drake TR-4 I was committed to repair. It has three 6JB6 in parallel to achieve 200..220 watts out at 80, less at the upper bands. To my surprise, the tubes (Penta brand) appear to be 6V but to take a lot more heater current than the data sheet specified 1.2A.
Have you had any experience with a similar thing?.

Best regards
Guillermo - LU8EYW.

--- In ham_amplifiers@..., "Robert B.
Bonner" <rbonner@...> wrote:

Flat and simple, aluminum is lighter. A fully loaded amplifier

ways a bunch

even with Aluminum used the construction.

Correct, but it takes a much thinner piece of steel to equal the same
strength of aluminum so they equal out close to the same. Generally,
20 gage steel is used in electronics chassis, and any aluminum is
much thicker. I forget what the aluminum gage is being used in most
amp chassis, but it's close to 1/8" thick or more.

You could get by with making the top socket level plate copper.

Stainless

and aluminum work well together, steel and aluminum corrode.

That's the problem with ground connections in amps using aluminum
chassis. The screws, washers, and some solder eyelets are steel.
Other eyelets are brass which is plated. The problem comes from
corrosion between the fastener-washer-eyelet and the aluminum. When
this happens, you either lose the connection or have a high
resistance at it. I've seen this happen in several squirelly acting
amps. I cleaned each connection and used new screws, etc which cured
the problem. A soldered connection though is worry free.

Steel used as electronics chassis is generally plated to stop
corrosion as in some transceivers. I'm not sure how zinc plated steel
would act with aluminum though as I have seen this used. Copper can
corrode forming copper oxide on the surface. However, copper was used
extensively in test equipment as shielding and the main chassis. In
them, all the grounds were soldered.

Copper tarnishes badly and with any moisture comes the green

goo... With any

condensation you could have a mess. I've never tested this for

galvanic

corrosion.

I don't believe there is any difference between aluminum and steel,

copper

whatever shielding...

Bob, I don't either, but some will argue different. I think steel
takes a bad rap for other probelms.

BOB DD

Best,

Will

Sorry, I need to be more specific... 3CX1200D7 (YU121)

denny

Flat and simple, aluminum is lighter. A fully loaded amplifier ways a bunch
even with Aluminum used the construction.

You could get by with making the top socket level plate copper. Stainless
and aluminum work well together, steel and aluminum corrode. Copper
tarnishes badly and with any moisture comes the green goo... With any
condensation you could have a mess. I've never tested this for galvanic
corrosion.

I don’t believe there is any difference between aluminum and steel, copper
whatever shielding...

BOB DD

All,

Here's my thoughts on the naming conventions when using the term
ground in a tube circuit. Ground, or chassis ground is the ground
that goes back to the power source. The chassis is most always tied
to this "ground" and is termed chassis ground. In most tube circuits,
except ones that have cathode bias, they tie the cathode to chassis
ground along with the negative lead from the HV supply. This is
therefore ground and is the 0 Vdc reference when measuring all
voltages. There actually may be a slight difference in voltage in a
directly heated cathode because of the resistance of the heater
transformer windings. That is when the C.T of the transformer is tied
to chassis ground. If the C.T is biased, then it changes things
completely.

When the cathode of a tube is biased, and the B- lead from the HV
supply is attached to it, and not chassis ground, this brings the
cathode to a negative potential when measured from chassis ground.
Terman, in his infinite wisdom mentions this in the Radio Engineers
Handbook. Here, he mentions that in a grounded grid amp, with the
cathode biased, the potential difference between the cathode and the
control grid which is tied to chassis ground is "less negative" and
not labled positive. This is due to folks misinterpreting the B- as
ground when in fact the only way it can be called ground is if the
cathode is directly tied to it, and there is no potential difference
between the two. Now I know all will say everything is referenced
from the cathode, but this is only the case in a cathode biased amp
where the cathode is not tied to the actual ground.

Most all the voltages of any circuit are read from the ground or
chassis ground whichever it may be for the 0 Vdc reference. The only
circuit that isn't is a cathode biased tube. Thus, any voltage on
either side of 0 Vdc is either a positive or negative voltage. Here,
I totally agree with what Terman said, in that he wouldn't call a
voltage positive between the control grid and cathode in a cathode
biased amp, even though there's a potential difference here. He says
it's less negative, not positive since to be positive, it would have
to show a positive reading from ground which it can not. However,
when placing the negative lead of a voltmeter to the cathode of a
cathode biased tube, and one to the grounded grid will show a
positive voltage. One here is actually viewing the difference between
0 Vdc (ground) and a negative voltage, not a positive one since the
positive lead of the meter attaches to chassis ground with the grid.
This even though an electron flow would happen between the cathode
and control grid over the difference in voltages. This could happen
between any grid that is at chassis ground or 0 Vdc and or above the
cathode since there's a potential difference. However, there's a
difference here on either side of chassis ground, positive and
negative. One also measures the screen voltage and bias for the
control grid to chassis ground. This is shown on any schematic. If
the cathode is biased, these voltages will be different when
measuring between chassis ground, or the grids, to the cathode. In a
directly grounded cathode like is used in many circuits, all voltages
are taken from chassis ground. So saying all voltages are measured
from the cathode kind of goes out the window.

In my opinion, a cathode biased tubes voltages (between the cathode
and chassis ground) should always be called less negative instead of
positive the same as Terman mentioned. This because the voltages can
never go over the 0 Vdc reference of chassis ground. One should never
use the term ground unless one is actually measuring a voltage to it.
Then, one has to use either negative or positive to describe the
voltage. Maybe one could use B- in place of ground in any description
for a cathode biased tube? This then will stop any confusion that may
exsist between a circuit where the cathode is actually grounded, and
one that's biased negative compared to chassis ground. This would
support all the definitions of voltage in either positive or
negative. If using "ground" to describe any circuit, it can be
confusing when a cathode biased tube circuit comes up when describing
voltages. Others may not agree, but I'm surely sticking with Terman
as he's the only one that has really made sense in describing what is
actually going on and sticking with the definitions.

Best,

Will

The way they're building most amps these days is to use a clam shell
type cabinet made of aluminum or like to C's placed together at 90
degree angles. The actual tube chassis is a box made with aluminum
just large enough to fit the tube sockets in the top of it. This then
is placed inside, generally at the rear of the cabinet. I would
rather have the top of this box-tube chassis made with either copper
or steel where I can solder the bypass caps directly to it or any
other ground connection. I've used steel in a lot of amps, and
personally I think it takes a bad rap over other probelms that are
not its fault. Of course copper would be the best, however there's
not enough steel here to hurt anything, and the rest of the cabinet
is aluminum anyhow. Aluminum is supposed to be better at shielding,
but I'm not convinced that is is that much better than steel. The
only difference would be the resistivity of the material, but the
area is so much that this would be really low. I've seen some big
amps built on steel chassis that were clean and shielded well without
spuriuos radiation problems. The major advantage to aluminum is that
it's a lot easier to work with and is why it's prefered in my
opinion. For years before aluminum was used, steel chassis were used
with very good results.

Best,

Will


--- In ham_amplifiers@..., "Peter Voelpel" <df3kv@...>
wrote:

Hi Will,

I wrote that the cathode is floating below ground potential.
Steel chassis I would never use in a high power amplifier at

places where

RF flows and no soldering at all.
Just copper and nuts+bolts, some times silver solder at coils.

73
Peter

_____

From: ham_amplifiers@...

[mailto:ham_amplifiers@...]

On Behalf Of craxd
Sent: Dienstag, 19. Dezember 2006 19:47
To: ham_amplifiers@...
Subject: [ham_amplifiers] Re: Grounded Screen Configuration



--- In ham_amplifiers@ <mailto:ham_amplifiers%40yahoogroups.com>
yahoogroups.com, "Peter Voelpel" <df3kv@>
wrote:

Hi Will,

All electrode voltages of a tube are referenced to the cathode.

I know this, see my last post.

If the cathode is directly grounded at the socket,

Grounded to chassis ground with the screen? The only way I can see
doing it is floating the cathode from chassis ground where the

screen

is tied to. There's no way to have a voltage difference if the
cathode and screen is tied together on the same ground. In your

case,

you would have a difference of 800 Vdc between the cathode and
chassis ground. In otherwords, your B- lead is isolated from

chassis

ground and tied to the cathode.

screen voltage is
supplied between cathode and ground (negative at the cathode).
Then normal screen voltage is supplied, you have a higher anode

voltage as

both voltage are in series and you don?t have the problem
with screen bypassing and an extremely stable condition if

driving

the tube

passive grid.

If the screen is bypassed correctly with capacitors at the tube
socket pins to chassis ground, I've never had any problems. That is
as long as the correct capacitance is used and all lead lengths are
as short as possible. Good ground connections are a must. I
personally don't like to use aluminum for the chassis around the

tube

socket, but rather use steel or copper. The reason being is I can
solder directly to the chassis. The rest of the chassis can be
aluminum though. One still has to worry about the connection

between

the two materials in how they're fastened together, etc. I've seen
too many connections come loose where a solder eyelet was attached

to

an aluminum chassis. This even when they use a wavy tooth lock
washer. A solder bonded connection is much better.

73
Peter

Best,

Will

开云体育