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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 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>

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... Any increase above 48 watts in causes the grid current to
soar with no change in the power out... I ran the grid up to 400 mils
<by accident> and got no increase in power out...

I remember some recent chatter about tube rebuilders on one of the
groups... Can anyone name the independent one <not owned by Eimac>?
Otherwise, I am off <well, that has been suspected for years> in
search of a new tube...

denny / k8do

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

Not very likely. What is the Q of the input tuned Pi-network?

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...

There is no limit for grid-I shown on Eimac's tech. spec sheets.

Any increase above 48 watts in causes the grid current to
soar with no change in the power out... I ran the grid up to 400 mils
<by accident> and got no increase in power out...

I remember some recent chatter about tube rebuilders on one of the
groups... Can anyone name the independent one <not owned by Eimac>?
Otherwise, I am off <well, that has been suspected for years> in
search of a new tube...

I never heard of anyone rebuilding a 3cx1200A7. ..
Since the 3cx1200A7 has a well-deserved reputation for squirrelliness - 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

- 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?

Jer

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

denny

--- 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

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

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 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

Yes, the 3K Ultra uses a transmission line transformer to convert the
~70 impedence at the cathode to 50 ohms... No tuned circuitry... It
has worked for ~8 years without problems, though the input swr is
always in the 1.6 to 1.9 range due to lack of reactance cancelling...

The talk with Rick at Eimac was informative <nice guy- who dates back
to the days of Bill Orr, etc.> Based on our talk I may have killed
the tube with kindness... My farm is fed with a 25kva transformer off
a HV underground line... My voltage has run in the 240-245 volt range
for years... When I got the amp I adjusted the taps on the filament
transformer so that it was 6.1 volts... I haven't looked at it in
recent years... In troubleshooting this amp we checked the filament
voltage and it was 6.02 volts idling and 5.92 under load... Turns out
the power compnay has dropped my HV feed a bit and I now only get 230
volts at the panel and even that probably drops under conditions of
high consumer demand back at the power plant... Rick believes the
filament has been poisoned by the underheat condition not maintaining
the thorium layer... I am going to try to reform the thorium layer
by running the filament at 7.5 volts for 5 minutes with no plate
voltage... Rick feels there is a small possibility that I can save
the filament... If I kill the tube in the process I will be no worse
off than now.. There is also the possibility that the vacuum is
going soft... If so no amount of tinkering will save it...

Once I try the reforming overheat I will get back with him... There
is a chance that one of his customers who had a batch of custom
3CX1200D7 built with a 1500 watt cooler <taller fins> has one left
over he will part with... The Henry has gobs of room inside the RF
compartment so a tall tube is not an issue... As I noted the tube is
making 1100 watts with 48 watts of drive so it is not totally gone...
But this amp routinely made 1500 out in the past... Since I do have
an understanding of what a dB is, I know that another 400 watts will
not be heard on the other end except for those really weak DX
contacts where 1 dB can make the difference... Not sure what I am
gong to do with this amp - retube it or?... I may look for someone
who will take it home and love it until the tube finally rolls over
and goes toes up...

In the meantime, there are a few contests coming up I want to play
with... I called QRO and they are not taking new orders for the
winter... Commander has over 20 amps on back order that he cannot get
tubes and/or transformers for and he estimates deivery will be March
07... I know what an estimated delivery time means...
I called Ten Tec and they have 3 amps built but not burned in yet
with two of them already sold... so I ordered the third one, Titan
III, Monday... Ya, ya, ya, I know that most of you don't think much
of Titan... OTOH, Scott says they have a plain vanilla Titan at PJ2
the guys just beat the crap out of during the contests, and it takes
a licking and keeps on ticking... If the III will make a solid 1500
out and work QSK with the new Orion, I will be satisified for now...
A bigger amp is in the works but that will take some time to build....

denny / k8do

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

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.

RICH SEZ.... Does it use g-g config?

### where have u been ? yes... it's GG. Now u know why I
collect amplifier manuals.

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 think

any of

the 3k/8 k ultra's were ever dead flat.... with that broadbanded
input.

RICH SEZ...There is no such thing as a broadbanded input for g-g.

Did Henry Radio get out of the amplifier business?

### agreed. The 'broadband tuned input' is a one off disaster.
they used 2 x xfmr's.. back to back.. on the 8 k ultra... and
simply stepped the Z way up... then stepped it right back down to
50 ohms. ... on all bands cept 25-30 mhz... where they stepped it
up.... but didn't step it back down as much... more like 75 ohms.

### Henry radio anounced 2 yrs ago.. that they lost their lease at
the LA factory where they been for the last 40 yrs. They are OUT
of the HF amateur amp business... and I believe also the
commercial/military HF amp business. They still are in the solid
state VHF/UHF amp business. Dunno, if they still support HF
amps.... with various bit's and pieces or not. Too bad... they did
make some excellent products over the years... like the 4 k
ultra. I bought one of their 10 kw ccs LP filters just a few yrs
ago.... with a 33 mhz cut off.... built like a tank.... with 7-16
DIN connectors... and bottom plates were 3/16" thick anodized AL...
and big 1/4" silver plated tubing coils.. Plus 8 x HT-57 NPO
caps in em.

### They also made excellent attenuator's.... in 1-2-3-4-5-6 db
increments... in both 35/100+ watt versions... 50 ohms in/out.
They shoulda just relocated the entire factory... too bad... end of
an era. Rumour has it that Rube Goldberg worked there at one point.

Later... Jim VE7RF

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

On Dec 20, 2006, at 1:40 PM, pentalab wrote:

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

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.

RICH SEZ.... Does it use g-g config?

### where have u been ? yes... it's GG. Now u know why I
collect amplifier manuals.

A broadband input plus g-g tells me that these guys are/were not very knowledgeable.

...
### well rich.. I guess eimac is right... since his input swr
dropped like a rock.... still not flat..... but I don't think

any of

the 3k/8 k ultra's were ever dead flat.... with that

broadbanded input.

RICH SEZ...There is no such thing as a broadbanded input for g-g.

Did Henry Radio get out of the amplifier business?

### agreed. The 'broadband tuned input' is a one off disaster.
they used 2 x xfmr's.. back to back.. on the 8 k ultra... and
simply stepped the Z way up... then stepped it right back down to
50 ohms. ... on all bands cept 25-30 mhz... where they stepped it
up.... but didn't step it back down as much... more like 75 ohms.

Most Hams who build electron tube amplifiers probably realize that the input-Z of a g-g stage typically fluctuates from a few tens of ohms at the negative peak of the driving cycle to a virtual open circuit at the positive peak. Thus, a flywheel / tuned circuit is required to even out the input-Z out and keep the exciter happy.

### Henry radio anounced 2 yrs ago.. that they lost their lease at
the LA factory where they been for the last 40 yrs. They are OUT
of the HF amateur amp business... and I believe also the
commercial/military HF amp business. They still are in the solid
state VHF/UHF amp business. Dunno, if they still support HF
amps.... with various bit's and pieces or not. Too bad... they did
make some excellent products over the years... like the 4 k
ultra. I bought one of their 10 kw ccs LP filters just a few yrs
ago.... with a 33 mhz cut off.... built like a tank.... with 7-16
DIN connectors... and bottom plates were 3/16" thick anodized AL...
and big 1/4" silver plated tubing coils.. Plus 8 x HT-57 NPO
caps in em.

Sounds appropriate.

### They also made excellent attenuator's.... in 1-2-3-4-5-6 db
increments... in both 35/100+ watt versions... 50 ohms in/out.
They shoulda just relocated the entire factory... too bad... end of
an era. Rumour has it that Rube Goldberg worked there at one point.

chortle


cheerz, Jim

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

I know what I paid for my 3KU brand new... When I look at the quality
of the materials, the hand made switching solenoids in the tank
circuit, the silver plated 1/4" tubing roller inductor the size of
your thigh, the thick aluminum cabinets, the milspec connectors and
the cable to the control head, etc., they had to have been barely
breaking even given their obvious material and labor costs... The
amp is built hell for stout... I suspect that losing their lease gave
them a graceful way to staunch the bleeding...

I understand where you are coming from Rich on the untuned input, yet
the amp always gets compliments on the rare occasions I get into a
roundtable on phone with the guys... And even Eimac during my phone
call to them complimented Henry for doing innovative things that no
one else in the industry did...

I have been through several Henry amps, 3K and 4K, and the last few
years they were in business when I called to talk to the techs no one
there spoke english anymore... And the answers I got made me suspect
they were winging it, rather than really knowing the amp... LA is a
ferociously expensive place to live and to do business - and
California taxation will spin your hat... Any tech who had electronic
skills could demand $25 or $30 an hour, and get it... Henry's
overhead had to be eating them... Had I been running the company I
would have moved it to Laramie Wyoming, or Depuke Ioway, in a heart
beat...

The remaining 3K Classic I have, with 3-500's, will sit there and
pump out 1500 watts of CW all day long... Of course, the plates glow
like a xmas tree doing it, but they seem to hang in there...

denny / k8do

Well, Santa brought me an $800 xmas present... I removed the HV lead
from the 3CX1200D7 and cooked the filament at 7.26 volts for 6
minutes... Eimac had suggested 7.5 volts for 5 minutes but 7.26 was
all I could get without going looking for the 220 Variac and
unsoldering a bunch of wires inside the Henry... For a moment I
started to pull the tube out on the bench and cobble up a test jig,
then basic laziness caught up with me <I had already put in a 12 hour
day, so cut me some slack>
Anyway, post toasty, the tube puts out 1700 watts for 74 watts of
drive and the grid current right on 200 mils.. Before the toasting
it put out 1100 watts with 48 watts of drive hitting 200 mils on the
grid... So for the moment all is well... Who knows how long the tube
will work... I have reset the filament to 6.6 volts for running,
which is right at the upper limit per Eimac... I did try it at 6.3
volts and saw a 120 watt drop on output... So the filament emission
current is sagging... At full output I am seeing the input swr at
1.6:1 through the input transformer...
I was going to calculate the grid dissipation then realized I don't
know the Grid to cathode voltage under load... We tried taking a DC
measurement off the filament to ground under load, but with the AC
superimposed on the cathode current I don't trust the numbers I see,
especially since there is a half volt, or more, difference from one
side of the filament compared to the other... So I don't know how to
calculate the dissipation unless I just assume that voltage from the
Eimac tube curves... Anyone?

denny / k8do