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On Sep 24, 2006, at 8:19 PM, Tony King - W4ZT wrote:

That's an excellent idea Bill. I will have to try that the next time I
test GS-35B's. Don't know if I will be able to see much with the ceramic
but I would bet it would be easy to see with glass tubes. Maybe someone
else could report on that one. One of these new small space age magnets
should produce enough magnetic field. Stuck on the end of a large tywrap
should make it safe enough.

What kind of flowers do you want, Tony?

73, Tony W4ZT

Bill Turner wrote:

ORIGINAL MESSAGE:

On Sun, 24 Sep 2006 13:38:32 -0400, Tony King - W4ZT
<w4zt-060920@...> wrote:

We had a discussion about fluorescence in ceramic tubes some time back
and I posted a few pictures of GS-35B's glowing in the dark
<>. The best explanation was electron bombardment
as opposed to soft X-rays. Just not enough voltage to accelerate the
electrons enough to generate the X-rays. Most of the pictures were taken
with less than 2500 Volts on the anode.

73, Tony W4ZT

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

One way to prove it once and for all would be to try to deflect the
beam with a magnet. Electrons would be deflected, x-rays would not.

Sound reasonable?

Bill, W6WRT

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On Sep 25, 2006, at 1:36 AM, pentalab wrote:

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

On Sep 24, 2006, at 5:05 AM, pentalab wrote:

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

wrote:

### getter's [per Eimac and Svetlana] are ALWAYS

working... as long as the fil is lit. HV + drive are not
part of the overall gettering process.

Rich- If this is the case, why not use the tubes as they are being
gettered? This has always been the way that I have done it.

### Hey Rich....... if you blow up ur new rebuilt Svetlana

4CX-10,000J... don't come whining to me !

### All I was trying to get at was.... if 16 guys say to

use 48 hrs to getter a new/rebuilt tube.... and anything less is

gonna be a problem... cuz they have tried many diff time
frames... who am I to argue?

Rich - I have run into a number of amateur radio dudes who advise
something that sounds semi-plausible, but instead of being based
in science, it turns out to be an artifice for promoting his guru
status by giving the appearance of having esoteric knowledge.

### Well these dudes were very adamant about the 48 hour
gettering process.

Wannabe gurus and "recognized amplifier experts" feel they have to be very adamant because if one of them admits to even a picovolt of fallibility, he fears that he will lose credibility as a guru with his faithful followers. However, in my view, just the opposite is true. Every human makes mistakes and those who deny they do are their own worst enemy. IOW, if one doesn't know about something, 'tis best to close mouth and open ears.
Example -- When I was planning to build the original "Plywood Box" amplifier two decades ago, I consulted with the greatest amplifier guru in Southern California. When the project was completed and the design errors were fixed, I realized that some of his advice was based on wrong guessing and he would have come out ahead by simply saying "I don't know" when it came to territory he didn't know about.

Forget the science.... real life practical
experience is what counts. The tube is good for 35,000 hrs
b4 a rebuild.....

8171s, and 3-500Zs are more like 20k-hrs IF the fil-V is kept to a minimum.

so what if u leave the filament on for 48
hrs... it can't do any harm.

The point is that the gettering isn't going to happen any better with the HV off as with the HV on. In fact, according to Will's research, up to a point, hotter is definitely better.

A few of these fellows have a
LOT of experience with those tubes....... Jerry at Economy
Electronics buys the entire production run of YC-243's from
Eimac each month [socketless 6000A7]. He told me the same
deal..... 48 hrs.... or u could easily experience trbl.

I know an automobile mechanic who advises changing oil/filter two and a half times as often as Toyota recommends. Who's right?

### Eimac tells me the YC-243's that come in to be rebuilt, none
have had a fried grid in em... that's just a side story.

## I don't have the time or patience to inadvertantly

destroy expensive new/rebuilt tubes.

Rich - I have probably never run filaments for more than a minute

before firing up a new 3-500Z or 8170.

### 3-500Z's need the anodes to show colour to getter em.....
so whether u run the new 3-500Z fil for just a minute or 48
hrs is irelevant.

### How many DOZENS of new 8170's have you fired up ???

the straw man

### You gotta be very carefull here Rich. Anecdotal experience
with just one of anything is no subsitute with experience
with hundreds of the same thing.

I remember the story of Chicken Little.

When a fellow who sells
literally hundreds of big metal triodes/tetrodes.... and has a lot
of experience with em sez 8 hrs is not enough to getter
em.. or XYZ will happen..and does,.... and to use 48 hrs min....
I tend to listen.

I high-pot new or used tubes before plugging one in. If a tube is gassy, I don't plug it in. As I see it, with the exception of tubes with a built in ion-pump, vacuum leakage current Never decreases and it can not be exorcised by an exoteric means.

### when guys tell me 1/2" tubing tank coils run so bloody
hot on 10m, they require 100-200 cfm....

Water-cooled Cu tubing tank coils and water-cooled vacuum capacitors are common in larger commercial amplifiers.

I tend to listen,,,and
not try an re-invent the wheel. [on 10m, you can easily be
dissipating 200w of heat... all of it into just a 2-3 turn
coil.... as opposed to 120 watts of heat on 20m..... and way
more turns on 20m to boot]. Actually 3/4" is better.... and
strap... laid flat... like a parasitic suppressor wound on a
globar is the best for a 10m tank coil.

Strap will have RF
flowing down both sides.... where as tubing only conducts on the
outside. 1.5" wide strap works superb... eq to 1"
tubing... and minimal stray C between turns.

Good points, Jim, but there's a bit more to it. Round tubing has uniform RF current distribution, while strap concentrates RF current at the edges. Thus, at the same current, tubing with the same surface area as strap will show less heating than the strap. For example, Cardwell rates 0.5" tubing at 40A while 0.5" strap is rated at 15A. However, there is a considerable space saving with strap, and it's easier to wind, so I prefer strap.

Jim VE7RF










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To me that is hard to believe.
I never recognized any emission current higher then a few microamps without
voltages on other electrodes of a tube.

Without anode voltage there will be only a cloud of electrons formed above
the catode.
There will be a large difference on the number of emitted electrons from the
cathode at a tube just heated and the one at full emission.
The emission goes up with the anode voltage and starts very low at almost
zero emission current up to the saturation point, which is certainly not
reached, as the tube is already well above dissipation limits before.
So it can?t be the SAME rate either at which the clock ticks.

73
Peter

________________________________

From: ham_amplifiers@... [mailto:ham_amplifiers@...]
On Behalf Of pentalab

How does ?the clock tick? when just the heater is lit and no

current flows?

### anode/grid current/drive power has nothing to do with
emmision. Take 2 x identical linear's..... one with just the
fil /blower on.[no HV no drive applied] ..and the 2nd linear
with HV on and drive applied [dead cxr]. The tube in each
amp will lose emmision at the SAME rate.

On Sep 25, 2006, at 12:58 AM, pentalab wrote:

--- In ham_amplifiers@..., "craxd" <craxd1@...> wrote:

Jim,

Did you ever get to speak to anyone at Eimac about where the

getters

were at in a 3-500Z? That's a question I'd say a few of us would

like

to find out about as I think there is some erroneous info floating
around on the net about it. One said it was the anode itself, but

it

doesn't get hot enough in my opinion to do it, and would actually

have

relaeased hydrogen gas if, a certain gettering material were

applied

to it. Any thoughts on this?

73,

Will

### No I have not. 1 e-mail to eimac ought end the
discussion . Rauch claims amperex etc... all use zirconium
coated anodes... and gettwring is done when tubes shoe
colour... aprx 800 deg C. I'm inclined to agree.

So how can a 3-500 be gettered by running the filament only?

A 3-500Z
has no internal getter........ so it's either the tube has
zirconium on the anode..... or it has NO getter at all !

Jim VE7RF






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On Sep 25, 2006, at 12:53 AM, pentalab wrote:

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

Hi Jim,

I understand that tube life is dependend on their vacuum and on

the emission

from the cathode such that material of it disappears until worn,

and then

the tube is probably send in for a new coating.
How does ?the clock tick? when just the heater is lit and no

current flows?

73, Peter

### anode/grid current/drive power has nothing to do with
emmision. Take 2 x identical linear's..... one with just the
fil /blower on.[no HV no drive applied] ..and the 2nd linear
with HV on and drive applied [dead cxr]. The tube in each
amp will lose emmision at the SAME rate.

### after XXX hours.... the tube in each amp will need to be
sent in for a rebuild.

### Hence.... 'when the fil is lit, the clock is ticking'

Amen, Jim, and when thoriated-tungsten fil-V is increased, the tock
ticks faster as a function of dV^23.4, so for every 3% increase in
filament V, useful emissive life is whacked 50%.

Jim VE7RF

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On Sep 24, 2006, at 2:09 PM, craxd wrote:

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

On Sep 24, 2006, at 8:40 AM, Bill Turner wrote:

ORIGINAL MESSAGE:

On Sun, 24 Sep 2006 12:05:38 -0000, "pentalab" <jim.thomson@...>
wrote:

### Are u talking about 3-500Z's and 4-1000's ???? [glass
tubes] I have had new 4-1000's that glowed blue. It was
not gas either.... it was an anomoly/defect in the glass....per
Eimac. The glass would glow blue.... only when drive applied.

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

I don't think this is a defect. Many tubes show a fluorescence on

the

inside of the glass when operating. I was told it was "soft" x-

rays

caused by electrons impacting the anode and then striking the

glass.

I have seen this on 807s running at 750v with this glow on Tx. Soft

I've seen this in sweep tubes also many times. The glass had a blue
glow in places where there were holes open in the anode.

In the presence of an electrostatic field - such as that at the anode, electrons do not travel in a straight path.

I think Rich
is correct on this that some electrons escape, and strike the glass.
However, if the electron is out there at the glass, how does it get
replaced back into the cathode?

X-rays are more like >10,000v.
As I see it, the effect is caused by electrons from the cathode
missing the anode, striking the glass, and bumping electrons in the
fluxing agent up an a higher orbit When the electrons slow down they

fall back to their normal orbit and emit visible photons.

Whether that is the real cause or not, I've seen it many times.
Nothing to worry about.

The tubes that do not fluoresce probably have a different mix of
compounds or elements in the glass.

Agreed. There are several different fluxing agents used in glass
recipes.

This should not be confused with a blue glow between the elements.
That is gas and is something to worry about.

What's to worry about?, it's done.

Bill, W6WRT



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Best,

Will







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On Sep 24, 2006, at 1:56 PM, craxd wrote:

Jim,

Did you ever get to speak to anyone at Eimac about where the getters
were at in a 3-500Z?

My take on gettering / gas contamination, or the lack thereof, is that it mainly came from a station who was trying to explain big-bang arcing in the output sections of HF/MF amplifiers by a means other than by an intermittent VHF parasite. However, since an arc in a near- vacuum is nearly silent acoustically-speaking, his internal-gas explanation of big-bang arcs did not wash. Other problems with his explanation is that tubes removed from amplifiers that sustained a big-bang arc typically show a normal vacuum on a high-potential tester, and that the VHF suppressor resistors from such amplifiers are often considerably higher in resistance than the marked value -- thereby suggesting the reason he didn't want.

That's a question I'd say a few of us would like
to find out about as I think there is some erroneous info floating
around on the net about it. One said it was the anode itself, but it
doesn't get hot enough in my opinion to do it,

Agreed, which is probably why the secret Admonishtrator (sic) bristled at your posts about this fly in his pie.

and would actually have
relaeased hydrogen gas if, a certain gettering material were applied
to it. Any thoughts on this?

73,

Will

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

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

Do getters stop working when the HV is applied? ... when the

drive is applied? ... or when both are applied?

### getter's [per Eimac and Svetlana] are ALWAYS working...
as long as the fil is lit. HV + drive are not part of the
overall process.

ANY and
all residual gas and junk is absorbed by the getter's... and
you will never get any surprises... like any arcing from
anode to the grounded grid !!

I've fired up several gassy tubes, the insides glowed blue, but

none of them arced to the grid.

### Are u talking about 3-500Z's and 4-1000's ???? [glass
tubes] I have had new 4-1000's that glowed blue. It was
not gas either.... it was an anomoly/defect in the glass....per
Eimac. The glass would glow blue.... only when drive applied.

### Then I have also seen 4-1000's that glowed blue INSIDE the
anode/screen/grid compartment..... dunno if that was with drive
applied or not...... that was too long ago.

### With a big ceramic triode/terode.... I highly suspect... If
it's gassy... and BOTH HV and drive are applied.... arcs MIGHT
occur between anode to screen... or anode to grid.

### If the vac isn't good and hard in the 1st place.... that
could easily create even more problems.

### I had several 4-1000's yrs ago... that looked like a smoke
bomb going off inside.... when the fil V was applied!! They had
either a lousy vac.... or..'had gone to air'.

### did u ever see a blue glow inside the ceramic portion of a
metal tube ?? Kinda tough to see..with the chimney on.

### All I was trying to get at was.... if 16 guys say to use
48 hrs to getter a new/rebuilt tube.... and anything less is
gonna be a problem... cuz they have tried many diff time
frames... who am I to argue?

### Svetlana claims their tubes are proccesed at a higher temp
than Eimac [during the construction of the tube]... one would
think the Svetlana tubes would have less of a 'gas' problem
than an Eimac ?

### The Svetlana tubes all use a 'spiral mesh fil' and
where all the mesh criss crosses... they are welded. ... so
u don't wanna slam the fil V on.. it can buckle the mesh fil
sideways..esp with over rated fil xfmrs [eg: I use a 80 A
rated fil xfmr on my 50 A rated 3000A7]......... another reason
to step start em.

## I don't have the time or patience to inadvertantly destroy
expensive new/rebuilt tubes.

Later... Jim VE7RF

...

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On Sep 24, 2006, at 7:36 PM, Bill Turner wrote:

ORIGINAL MESSAGE:

On Sun, 24 Sep 2006 17:59:19 -0700, R L Measures <r@...> wrote:

They can't reverse direction quick enough?

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

Perhaps so, but if they can accelerate to a certain speed in the half
inch or so between cathode and anode, why could they not decelerate an
equal amount a half inch after passing the anode? They would be
stopped in mid-space and immediately return to the anode like good
little electrons should. :-)

The evidence is that they strike glass, causing it ti fluoresce. I've seen 4-1000As with glass that turned pale brown where electrons had been banging it.

Or maybe the glass is too close to the anode so there is no time for
reversal before impacting the glass?

Bill, W6WRT





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On Sep 24, 2006, at 7:25 PM, Bill Turner wrote:

ORIGINAL MESSAGE:

On Sun, 24 Sep 2006 13:38:32 -0400, Tony King - W4ZT
<w4zt-060920@...> wrote:

We had a discussion about fluorescence in ceramic tubes some time back
and I posted a few pictures of GS-35B's glowing in the dark
<>. The best explanation was electron bombardment
as opposed to soft X-rays. Just not enough voltage to accelerate the
electrons enough to generate the X-rays. Most of the pictures were taken
with less than 2500 Volts on the anode.

73, Tony W4ZT

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

One way to prove it once and for all would be to try to deflect the
beam with a magnet. Electrons would be deflected, x-rays would not.

Sound reasonable?

quite, provided the magnet is on a long enough, insulated stick.

Bill, W6WRT



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

On Sep 24, 2006, at 5:05 AM, pentalab wrote:

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

wrote:

### getter's [per Eimac and Svetlana] are ALWAYS

working... as long as the fil is lit. HV + drive are not
part of the overall gettering process.

Rich- If this is the case, why not use the tubes as they are being
gettered? This has always been the way that I have done it.

### Hey Rich....... if you blow up ur new rebuilt Svetlana

4CX-10,000J... don't come whining to me !

### All I was trying to get at was.... if 16 guys say to

use 48 hrs to getter a new/rebuilt tube.... and anything less is

gonna be a problem... cuz they have tried many diff time
frames... who am I to argue?

Rich-I have run into a number of amateur radio dudes who advise

something that sounds semi-plausible, but instead of being based
in science, it turns out to be an artifice for promoting his guru
status by giving the appearance of having esoteric knowledge.

### Well these dudes were very adamant about the 48 hour
gettering process. Forget the science.... real life practical
experience is what counts. The tube is good for 35,000 hrs
b4 a rebuild..... so what if u leave the filament on for 48
hrs... it can't do any harm. A few of these fellows have a
LOT of experience with those tubes....... Jerry at Economy
Electronics buys the entire production run of YC-243's from
Eimac each month [socketless 6000A7]. He told me the same
deal..... 48 hrs.... or u could easily experience trbl.

### Eimac tells me the YC-243's that come in to be rebuilt, none
have had a fried grid in em... that's just a side story.

## I don't have the time or patience to inadvertantly

destroy expensive new/rebuilt tubes.

Rich - I have probably never run filaments for more than a minute

before firing up a new 3-500Z or 8170.

### 3-500Z's need the anodes to show colour to getter em.....
so whether u run the new 3-500Z fil for just a minute or 48
hrs is irelevant.

### How many DOZENS of new 8170's have you fired up ???

### You gotta be very carefull here Rich. Anecdotal experience
with just one of anything is no subsitute with experience
with hundreds of the same thing. When a fellow who sells
literally hundreds of big metal triodes/tetrodes.... and has a lot
of experience with em sez 8 hrs is not enough to getter
em.. or XYZ will happen..and does,.... and to use 48 hrs min....
I tend to listen.

### when guys tell me 1/2" tubing tank coils run so bloody
hot on 10m, they require 100-200 cfm.... I tend to listen,,,and
not try an re-invent the wheel. [on 10m, you can easily be
dissipating 200w of heat... all of it into just a 2-3 turn
coil.... as opposed to 120 watts of heat on 20m..... and way
more turns on 20m to boot]. Actually 3/4" is better.... and
strap... laid flat... like a parasitic suppressor wound on a
globar is the best for a 10m tank coil. Strap will have RF
flowing down both sides.... where as tubing only conducts on the
outside. 1.5" wide strap works superb... eq to 1"
tubing... and minimal stray C between turns.

Jim VE7RF

Jim,

Below is a quote from Terman on this subject.

"Zirconium is also a useful metal in this regard. Zirconium at 1400
deg C will absorb copius quantities of such gasses as oxygen,
nitrogen, carbon monoxide, and carbon dioxide. The optimum temperature
for taking up hydrogen is 350 deg C, and at higher temperatures
hydrogen begins to be given off by the metal. As a result of these
properties it is possible to maintain an extremely high vacuum,
provided that there is zirconium in the tube at these two
temperatures. This can be accomplished either by employing two
zirconium filaments with different filament currents, or by using a
single piece of zirconium in which different parts of the metal are
raised to different temperatures, so that the temperature range
extends from 300 to 1400 deg C".

Terman references this;

Zirconium and its compounds with a high melting point. Phillips Tech
Journal, Worlds fair issue, 1939, by J. D. Fast.

According to the temp. chart by Tempil, 1400 deg C is yellow in color.
300 deg c is no color. I don't know of any 3-500z that would run this
color without melting the glass. Tempil manufacturers temperature
detection and measurement devices and the tempil stick paints. A copy
of the chart can be had here;



Thanks,

Will


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

--- In ham_amplifiers@..., "craxd" <craxd1@> wrote:

Jim,

Did you ever get to speak to anyone at Eimac about where the

getters

were at in a 3-500Z? That's a question I'd say a few of us would

like

to find out about as I think there is some erroneous info floating
around on the net about it. One said it was the anode itself, but

it

doesn't get hot enough in my opinion to do it, and would actually

have

relaeased hydrogen gas if, a certain gettering material were

applied

to it. Any thoughts on this?

73,

Will

### No I have not. 1 e-mail to eimac ought end the
discussion . Rauch claims amperex etc... all use zirconium
coated anodes... and gettwring is done when tubes shoe
colour... aprx 800 deg C. I'm inclined to agree. A 3-500Z
has no internal getter........ so it's either the tube has
zirconium on the anode..... or it has NO getter at all !

Jim VE7RF

--- In ham_amplifiers@..., "craxd" <craxd1@...> wrote:

Jim,

Did you ever get to speak to anyone at Eimac about where the

getters

were at in a 3-500Z? That's a question I'd say a few of us would

like

to find out about as I think there is some erroneous info floating
around on the net about it. One said it was the anode itself, but

it

doesn't get hot enough in my opinion to do it, and would actually

have

relaeased hydrogen gas if, a certain gettering material were

applied

to it. Any thoughts on this?

73,

Will

### No I have not. 1 e-mail to eimac ought end the
discussion . Rauch claims amperex etc... all use zirconium
coated anodes... and gettwring is done when tubes shoe
colour... aprx 800 deg C. I'm inclined to agree. A 3-500Z
has no internal getter........ so it's either the tube has
zirconium on the anode..... or it has NO getter at all !

Jim VE7RF

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

Hi Jim,

I understand that tube life is dependend on their vacuum and on

the emission

from the cathode such that material of it disappears until worn,

and then

the tube is probably send in for a new coating.
How does ?the clock tick? when just the heater is lit and no

current flows?

73, Peter

### anode/grid current/drive power has nothing to do with
emmision. Take 2 x identical linear's..... one with just the
fil /blower on.[no HV no drive applied] ..and the 2nd linear
with HV on and drive applied [dead cxr]. The tube in each
amp will lose emmision at the SAME rate.

### after XXX hours.... the tube in each amp will need to be
sent in for a rebuild.

### Hence.... 'when the fil is lit, the clock is ticking'

Jim VE7RF

That's an excellent idea Bill. I will have to try that the next time I test GS-35B's. Don't know if I will be able to see much with the ceramic but I would bet it would be easy to see with glass tubes. Maybe someone else could report on that one. One of these new small space age magnets should produce enough magnetic field. Stuck on the end of a large tywrap should make it safe enough.

73, Tony W4ZT

Bill Turner wrote:

ORIGINAL MESSAGE:

On Sun, 24 Sep 2006 17:59:19 -0700, R L Measures <r@...> wrote:

They can't reverse direction quick enough?

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

Perhaps so, but if they can accelerate to a certain speed in the half
inch or so between cathode and anode, why could they not decelerate an
equal amount a half inch after passing the anode? They would be
stopped in mid-space and immediately return to the anode like good
little electrons should. :-)

Or maybe the glass is too close to the anode so there is no time for
reversal before impacting the glass?

Bill, W6WRT

ORIGINAL MESSAGE:

On Sun, 24 Sep 2006 13:38:32 -0400, Tony King - W4ZT
<w4zt-060920@...> wrote:

We had a discussion about fluorescence in ceramic tubes some time back
and I posted a few pictures of GS-35B's glowing in the dark
<>. The best explanation was electron bombardment
as opposed to soft X-rays. Just not enough voltage to accelerate the
electrons enough to generate the X-rays. Most of the pictures were taken
with less than 2500 Volts on the anode.

73, Tony W4ZT

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

One way to prove it once and for all would be to try to deflect the
beam with a magnet. Electrons would be deflected, x-rays would not.

Sound reasonable?

Bill, W6WRT

I use HN connectors for high voltage and use RG213 as a conductor. the chassis side I found a mate with a long leakage path. wa1gfz

pentalab wrote:

On Sep 24, 2006, at 10:25 AM, Bill Turner wrote:

ORIGINAL MESSAGE:

On Sun, 24 Sep 2006 10:12:39 -0700, R L Measures <r@...> wrote:

I have seen this on 807s running at 750v with this glow on Tx. Soft
X-rays are more like >10,000v.
As I see it, the effect is caused by electrons from the cathode
missing the anode, striking the glass, and bumping electrons in the
fluxing agent up an a higher orbit When the electrons slow down they
fall back to their normal orbit and emit visible photons.

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

Wouldn't electrons which "miss" the anode be immediately attracted
back to the outside of the anode? Why would they continue out to the
glass instead of circling back?

They can't reverse direction quick enough?

Some interesting physics here.

Bill, W6WRT



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

On Sep 24, 2006, at 8:40 AM, Bill Turner wrote:

ORIGINAL MESSAGE:

On Sun, 24 Sep 2006 12:05:38 -0000, "pentalab" <jim.thomson@...>
wrote:

### Are u talking about 3-500Z's and 4-1000's ???? [glass
tubes] I have had new 4-1000's that glowed blue. It was
not gas either.... it was an anomoly/defect in the glass....per
Eimac. The glass would glow blue.... only when drive applied.

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

I don't think this is a defect. Many tubes show a fluorescence on

the

inside of the glass when operating. I was told it was "soft" x-

rays

caused by electrons impacting the anode and then striking the

glass.

I have seen this on 807s running at 750v with this glow on Tx. Soft

I've seen this in sweep tubes also many times. The glass had a blue
glow in places where there were holes open in the anode. I think Rich
is correct on this that some electrons escape, and strike the glass.
However, if the electron is out there at the glass, how does it get
replaced back into the cathode?

X-rays are more like >10,000v.
As I see it, the effect is caused by electrons from the cathode
missing the anode, striking the glass, and bumping electrons in the
fluxing agent up an a higher orbit When the electrons slow down they

fall back to their normal orbit and emit visible photons.

Whether that is the real cause or not, I've seen it many times.
Nothing to worry about.

The tubes that do not fluoresce probably have a different mix of
compounds or elements in the glass.

Agreed. There are several different fluxing agents used in glass
recipes.

This should not be confused with a blue glow between the elements.
That is gas and is something to worry about.

What's to worry about?, it's done.

Bill, W6WRT



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Best,

Will

Gettering of those and similar tubes is done by the anode coating.
One reason they have to be driven red, which is about 800°C

73
Peter

________________________________

Subject: [ham_amplifiers] Re: How to Getter a 3CX-3000A7 / 6000 / 10,000 ,
etc !

Did you ever get to speak to anyone at Eimac about where the getters
were at in a 3-500Z? That's a question I'd say a few of us would like
to find out about as I think there is some erroneous info floating
around on the net about it. One said it was the anode itself, but it
doesn't get hot enough in my opinion to do it, and would actually have
relaeased hydrogen gas if, a certain gettering material were applied
to it. Any thoughts on this?