813 warm up time
 

How long after applying filament voltage till the 813 is ready to transmit?
Is it like a 3-500 or do I have to wait 30 seconds or so?

Rick K2XT

813 warm up time
 

"Rick" wrote in message
...
How long after applying filament voltage till the 813 is ready to
transmit? Is it like a 3-500 or do I have to wait 30 seconds or so?

Rick K2XT

Apply filament, bias, screen and plate Voltage and start talking.

W4ZCB

813 warm up time
 

Wait at least 30 seconds. The 813 doesn't have instant heating filaments
like the 3-500z.

73

Ralph VE3BBM
"Rick" wrote in message
...
How long after applying filament voltage till the 813 is ready to
transmit? Is it like a 3-500 or do I have to wait 30 seconds or so?

Rick K2XT

813 warm up time
 

The 813 filament is constructed of thoriated tungsten. One of the
characteristics of this type filament is "instant" on.

See http://www.w8ji.com/vacuum_tubes_and...e_failures.htm and look
under thoriated filament.

You do want the filament to heat up and that probably means a second or two.
I remember Bill Orr wrote an article about failure of the 3-500 ( which is
considered instant on also). Some individual had a number of tubes fail and
kept sending them back under warranty. Finally Eimac called him and learned
that the chap was turning the tube filaments off between transmissions and
turning them on immediately before each transmission.

So, do not use either tube for break in cw by keying the filament.

73, Colin K7FM

813 warm up time
 

COLIN LAMB wrote:
Finally Eimac called him and learned
that the chap was turning the tube filaments off between transmissions and
turning them on immediately before each transmission.

So, do not use either tube for break in cw by keying the filament.

73, Colin K7FM




I have to wonder what the keying waveform might have looked like.
Probably added a unique sound to his signal. Something like a modified
banana-boat swing, for lack of a better description?
de K3HVG

813 warm up time
 

On Tue, 1 Apr 2008, Rick wrote:

How long after applying filament voltage till the 813 is ready to transmit?
Is it like a 3-500 or do I have to wait 30 seconds or so?

Rick K2XT



When the glow is up to bright orange, then you are ready. If you apply the
filament voltage without "management" (i.e. a slow increase over, say 5-10
seconds), the tube should be ready for transmit in, like, about 1-2
seconds. In a heater cathode (rather than a filament cathode), you need to
wait for that thin "coat" to come up to a dull orange and that can be half
a minute or so depending on the tube.

813 warm up time
 

In article m,
A wrote:


On Tue, 1 Apr 2008, Rick wrote:

How long after applying filament voltage till the 813 is ready to transmit?
Is it like a 3-500 or do I have to wait 30 seconds or so?


When the glow is up to bright orange, then you are ready. If you apply the
filament voltage without "management" (i.e. a slow increase over, say 5-10
seconds), the tube should be ready for transmit in, like, about 1-2
seconds. In a heater cathode (rather than a filament cathode), you need to
wait for that thin "coat" to come up to a dull orange and that can be half
a minute or so depending on the tube.

Note that slow turn-on will radically increase the lifetime of these tubes
if you're using them below full power level. An inrush current limiter
in series with the filament only costs a dollar or two and can easily pay
for itself a hundred times over.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

813 warm up glow
 

An inrush current limiter
in series with the filament only costs a dollar or two and can easily pay
for itself a hundred times over.

Hang on here. Do you know what 813s cost these days? Still only around $10
!!
I got two at a hamfest last week. Got them hooked up to a filament xfmr,
and let them cook for an hour. Boy are they sure beautiful sitting there
glowing in the dark. They seem to be saying to me, "Hey we've been waiting
for 60 years to get a chance to make some RF!"
I also have 2kv waiting. So next step is to jury rig them up and see if
they draw plate current, with a little bias control, before I commit to
putting them in a new homebrew amp.
Since I just finished an 8877 amp this winter I am a little cautious and
aprehensive about hamfest tubes, because when I first fired up the 8877 with
4kv I got just that - fire. Seems the "I think it is good" tube a guy gave
me actually had a grid-plate short. Took a couple weeks to clean up THAT
mess. Fun stuff.
Thanks for all the replies, OTs.

73

Rick K2XT

813 warm up time
 

On Thu, 3 Apr 2008, Scott Dorsey wrote:

In article m,
A wrote:


On Tue, 1 Apr 2008, Rick wrote:

How long after applying filament voltage till the 813 is ready to transmit?
Is it like a 3-500 or do I have to wait 30 seconds or so?


When the glow is up to bright orange, then you are ready. If you apply the
filament voltage without "management" (i.e. a slow increase over, say 5-10
seconds), the tube should be ready for transmit in, like, about 1-2
seconds. In a heater cathode (rather than a filament cathode), you need to
wait for that thin "coat" to come up to a dull orange and that can be half
a minute or so depending on the tube.

Note that slow turn-on will radically increase the lifetime of these tubes

1. I recall a research topic handout mentioned in a QST from maybe 2
decades ago that said this but did not give actual numbers. Does anyone
have something specific in terms of what they call "radical"?

2. I also recall relatively little _actual_ discussion, from my SWLing
days on the ham bands 50 years ago, of people complaining about blowing
out their filaments sooner than they would be happy about, so do any of
you guys have any real life experience with this (instead of passing on
"conventional wisdom" that has been passed on as conventional wisdom by
everyone else that passes on conventional wisdom)?

3. Usually tube/filament lifetime is something like "insurance"
statistics. There will be an "S"-shaped curve with some characteristics
and this means a lot of filament lifetime experience will only show up in
fairly large populations.

4. For the record, I bought, some years ago, three Chinese 813s, brand
new, and after six months, one of two of them blew a filament (I barely
noticed it since at the end of the QSO I noticed my plate current was
running half of what is should have been) in my pair-813 linear (with
variac on the filament transformer).

5. Inrush currents will often be, already, limited to some degree because
filament cold resistance will be lower than hot resistance and most of the
secondary voltage will appear across secondary resistance which will be
almost identical either warm or cold. For power transformer powered
linears (etc), the HV is dumping into a string of electrolytics thus
building in, perhaps, 100-200 (?) milliseconds of "delayed" or "limited"
inrush current because that part of the transformer is
temporarily "overloaded."

6. How many of you guys with 3-500Z and 811 amplifiers (572-Bs, 4-X, etc,
and there are a lot out there) are replacing one or more of your tubes every
year or two because one or more filaments won't light up the next time you
turn on your rig? How many of you guys have the same tubes in your
amplifiers for a decade or more and the filaments are still lighting up
just fine and RF output (and not on "pushed" tubes, either) is also just
fine?

Guys, how about some extended discussion on this? And, I've had a few of
all of these tubes at one time or the other almost since the beginning of
my haming before 1960 and never lost a filament till the Chinese 813.

P.S. The Chinese 813 had crappy soldering work on the pins at the bottom
of the tube, too. The other Chinese 813 is still running fine. I have some
Chinese 811s, too, and their pins are better soldered. Russkie 811s look
and work fine, too. I replaced the burned out 813 with a used 813 from a
hamfest (an old brand I forgot) but it has a darker "tinge" inside, but
the RF amps out are just fine.


if you're using them below full power level. An inrush current limiter
in series with the filament only costs a dollar or two and can easily pay
for itself a hundred times over.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

813 warm up time
 

A wrote:

1. I recall a research topic handout mentioned in a QST from maybe 2
decades ago that said this but did not give actual numbers. Does anyone
have something specific in terms of what they call "radical"?

On the 813, I don't know. But Eimac used to have a little handout on
filament regulation of their planar grid tubes; it talked both about
small static increases in current severely shortening lifetime as well
as inrush current issues. It's worth looking up and is probably on the
Eimac website.

2. I also recall relatively little _actual_ discussion, from my SWLing
days on the ham bands 50 years ago, of people complaining about blowing
out their filaments sooner than they would be happy about, so do any of
you guys have any real life experience with this (instead of passing on
"conventional wisdom" that has been passed on as conventional wisdom by
everyone else that passes on conventional wisdom)?

I usually lose filaments before I lose emission on power tubes, but I
tend to run well below rated power. If I were running at rated power,
I might feel very differently.

3. Usually tube/filament lifetime is something like "insurance"
statistics. There will be an "S"-shaped curve with some characteristics
and this means a lot of filament lifetime experience will only show up in
fairly large populations.

4. For the record, I bought, some years ago, three Chinese 813s, brand
new, and after six months, one of two of them blew a filament (I barely
noticed it since at the end of the QSO I noticed my plate current was
running half of what is should have been) in my pair-813 linear (with
variac on the filament transformer).

This is probably the result of a manufacturing defect in the filament,
and inrush-current limiting may not have done much good anyway there.

5. Inrush currents will often be, already, limited to some degree because
filament cold resistance will be lower than hot resistance and most of the
secondary voltage will appear across secondary resistance which will be
almost identical either warm or cold. For power transformer powered
linears (etc), the HV is dumping into a string of electrolytics thus
building in, perhaps, 100-200 (?) milliseconds of "delayed" or "limited"
inrush current because that part of the transformer is
temporarily "overloaded."

Could well be... the sag due to charging the caps could well provide
effective soft startup. It might be worth measuring to see.

6. How many of you guys with 3-500Z and 811 amplifiers (572-Bs, 4-X, etc,
and there are a lot out there) are replacing one or more of your tubes every
year or two because one or more filaments won't light up the next time you
turn on your rig? How many of you guys have the same tubes in your
amplifiers for a decade or more and the filaments are still lighting up
just fine and RF output (and not on "pushed" tubes, either) is also just
fine?

I would suspect more people lose tubes due to bad emission than to filament
failures, but I also suspect people tend to be running finals hard out
there.

Guys, how about some extended discussion on this? And, I've had a few of
all of these tubes at one time or the other almost since the beginning of
my haming before 1960 and never lost a filament till the Chinese 813.

P.S. The Chinese 813 had crappy soldering work on the pins at the bottom
of the tube, too. The other Chinese 813 is still running fine. I have some
Chinese 811s, too, and their pins are better soldered. Russkie 811s look
and work fine, too. I replaced the burned out 813 with a used 813 from a
hamfest (an old brand I forgot) but it has a darker "tinge" inside, but
the RF amps out are just fine.

Which factory did the Chinese one come from? I have had nothing but trouble
with Shugang products, but I don't know if the 813s are from Shugang or not.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

813 warm up glow
 

On Thu, 3 Apr 2008, Rick wrote:

An inrush current limiter
in series with the filament only costs a dollar or two and can easily pay
for itself a hundred times over.

Hang on here. Do you know what 813s cost these days? Still only around $10
!!
I got two at a hamfest last week. Got them hooked up to a filament xfmr,
and let them cook for an hour. Boy are they sure beautiful sitting there
glowing in the dark. They seem to be saying to me, "Hey we've been waiting
for 60 years to get a chance to make some RF!"
I also have 2kv waiting. So next step is to jury rig them up and see if
they draw plate current, with a little bias control, before I commit to
putting them in a new homebrew amp.
Since I just finished an 8877 amp this winter I am a little cautious and
aprehensive about hamfest tubes, because when I first fired up the 8877 with
4kv I got just that - fire.

Fuses in primaries and secondaries of plate transformers are your friends.

Variacs feeding the primary of the plate transformer (and with an ammeter)
is a good idea if you start out with low voltage on the primary, and pay
very close attention to all of your meters.

It is better to have more meters than not enough meters.

Sometimes an ohmmeter check on pins of tubes, BEFORE you do the smoke
test, is wise (I have done smoke tests where I got smoke, too).

Seems the "I think it is good" tube a guy gave
me actually had a grid-plate short.

I have had the experience, at hamfests, where, after money goes to the guy
and the thing goes to me, then he tells me "Oh, by the way,..(fill in
the blank)...."

Took a couple weeks to clean up THAT
mess. Fun stuff.
Thanks for all the replies, OTs.

After deciding to build a linear, the decision came down to the 813 for
the following reasons:

1. Large glass tubes need no special socket or chimney.
2. Tube manual says no forced-air cooling is needed.
3. Sockets are cheap. Plate capes are cheap.
4. Tube is cheap.
5. Filament cathodes are "instant on" whereas heater cathodes need warm-up
time.
6. Large tubes generally mean old-fashioned large grids and that means a
larger margin for error (i.e. overloaded grid dissipation) than those new
small sexy expensive small metal-ceramic tubes with dinky, flimsy, small
grids that vaporize if you accidentally overdrive them for more than 1-2
milliseconds (I've heard guys talk about this on the air).
7. I have no fan on my 2x813 G-G amp, and it is very nice and quiet
(unlike three other commercial linears I've had with objectionable fan noise).

Pictures of some of my stuff at: http://w4pon.freeshell.org
Not all that pretty but it all works and I know how to fix it because I
built it.

73

Rick K2XT

813 warm up time
 

If you are firing up the tube for the first time in many years, let it bake
with full filament voltage for a few hours to allow the vacuum to stabilize
and degas.

After the initial baking session from then on a second after filament
voltage is applied, you can apply all voltages for transmit.

Chuck...K1KW


"Rick" wrote in message
...
How long after applying filament voltage till the 813 is ready to
transmit?
Is it like a 3-500 or do I have to wait 30 seconds or so?

Rick K2XT

813 warm up time
 

If you are firing up the tube for the first time in many years, let it
bake
with full filament voltage for a few hours to allow the vacuum to
stabilize
and degas.

I have done that and all still appears well. Even found a 10 volt, 16 amp
transformer
in the junkbox. Before I commit to using these tubes in a HB amp I will see
if they pull
plate current, and use a grid bias supply to control current. I have a
variac to control
plate current.
Tnx

Rick K2XT

813 warm up time
 

RCA took out an ad in the 1942 Radio Handbook. This, of course, was a
wartime publication.

The title to the article is "How to make transmitting tubes last longer."
They state:

"Long life - not maximum output - is the keynote of transmitting tube
operation today in many services where, because of war restrictions, it may
prove difficult to replace tubes that wear out. For tube types using pure
tungston, a 5% decrease in filament voltage will dobule tube life... Care
should always be taken in starting up tungsten filaments. Never should the
filament current exceed, even momentarily, a value of more than 150% of
normal.

For types using thoriated-tungsten filaments and oxide coated filaments, the
filament may be operated on the low side - as much as 5% below normal
voltage if the loading is light. The filament voltage should be increased
gradually to maintain output. Toward the end of life, additional service
may be obtained by operating the filament above its rated voltage."

The 813 has a thoriated-tungsten filament.

73, Colin K7FM

813 warm up time
 

On Sat, 5 Apr 2008, COLIN LAMB wrote:

RCA took out an ad in the 1942 Radio Handbook. This, of course, was a
wartime publication.

The title to the article is "How to make transmitting tubes last longer."
They state:

"Long life - not maximum output - is the keynote of transmitting tube
operation today in many services where, because of war restrictions, it may
prove difficult to replace tubes that wear out. For tube types using pure
tungston, a 5% decrease in filament voltage will dobule tube life... Care
should always be taken in starting up tungsten filaments. Never should the
filament current exceed, even momentarily, a value of more than 150% of
normal.

For types using thoriated-tungsten filaments and oxide coated filaments, the
filament may be operated on the low side - as much as 5% below normal
voltage if the loading is light. The filament voltage should be increased
gradually to maintain output. Toward the end of life, additional service
may be obtained by operating the filament above its rated voltage."

The 813 has a thoriated-tungsten filament.

73, Colin K7FM


The key issue which is not discussed at all above is that you have to look
at _some_ sample population to see the effect of lower filament voltage on
increased filament life. The question I ask, again, is how many guys out
there with filament cathode power tubes have had filaments blow out
(compared, say, with decrease in power output, or internal shorts that
blow fuses) in some manner that one might hypothesize is due to filament
warmup being too fast. Remember, I had one 813 filament open up on me even
though I was going from zero to ten volts, slowly over about ten seconds,
and on a Chinese 813 about one year old. So, I conclude, on a sample size
of one, that a filament can blow even if you raise filament voltage
slowly. Oh, yes, I also slowly decrease filament voltage to zero, too,
when I shut down the station. And, I'll remind everyone that I've had lots
of amplifiers in my ham career, and with no inrush protection, and never
lost a filament. I'd still like to hear from others about this.

Regarding higher filament voltages, I remember as a kid that we had a TV
set where the picture tube cathode emission deteriorated after some years
of use thus causing a weak picture (white areas were gray, gray areas were
black) and they had these little filament voltage boosters that caused the
filament to heat up to hotter temperatures thust restoring cathode
emission for some unknown additional period of time (I think the voltage
boost was from 6.3 vac to maybe 7.5 or so) since a hotter filament should
burn out sooner. Interestingly, we were still using that TV, every night,
for another three years. Again, a sample population of one. However, the
picture brightness did come back to fully normal levels.

In my own goofing off, I have raised filament voltage on a 6.3 v
expendable tube up to 18 volts, over a period of about one minute, before
it blew out the filament. It got quite bright. I have had momentary
mistakes where I have put 12.6 volts on filaments of 6.3 volt tubes for
periods of 10-20 seconds (turning off when seeing the filament get
abnormally bright) with no apparent effect on tube lifetime. Sample size:
maybe 3-4 tubes.

I had, once long ago, a tube hi-fi amplifier on which I put a variac and
was somewhat surprised that I still got power output even with 85-90 vac
going in, and over prolonged periods of time (Down at 75-80 vac, audio
droped off and distortion came up).

Surely there are a few people out there who have done some actual
(experimental) playing around with their tubes and can tell some stories
instead of passing on technical rumors.

813 warm up time
 

My Collins KWM-2 uses a home brew power supply. Step start on filaments -
at correct voltage and no high voltage for 60 seconds. Same tubes in it for
30 years. I think the only two power amplifier tubes that failed were
dropped on the floor. Some amplifiers adjusted the filament voltage to be
correct and some were never measured.

I ran a 3 x 813 amp for years and never changed the tubes or even measured
the filament voltage. Just used a transformer with the rated voltage and
called it good. Unless the filament transformer has a current rating much
higher than the demands of the amplifier tubes, the surge will probably be
ok.

Incidently, the home brew equipment looks practical. I built a vfo using
the Collins 70H3. The problem with it is that it covers 1.5 to 3 MHz with
10 turns. That is 150 kHz per turn. Bad for a linear dial. I used a 8:1
reduction gear and a crystal controlled mixer to cover 5 to 6.5 MHz, then
limited use to 5 - 5.5 MHz. That was coupled in as the second vfo for my
Drake TR-5, so when I switch it in, the Drake digital dial displays the
frequency. Extremely stable. Oh, I converted it to solid state, also,
which is easy to do. There is one minor problem in that there are no stops
on the dial. Not a problem for me, but if some kid came in and started
twisting, he could break something. Oh well, you need to take some risks in
life.

73, Colin K7FM

813 warm up time
 

A wrote:

The key issue which is not discussed at all above is that you have to
look at _some_ sample population to see the effect of lower filament
voltage on increased filament life. The question I ask, again, is how
many guys out there with filament cathode power tubes have had filaments
blow out (compared, say, with decrease in power output, or internal
shorts that blow fuses) in some manner that one might hypothesize is due
to filament warmup being too fast.

If I understand your request, you would like us to abandon the advice of
the tube manufacturers, and instead use our own anecdotal accounts of
tube filament failures?

It is unlikely that any of us have run herd on as large a sample set of
tubes as the manufacturers did. Clearly the chance of filament failure
among transmitting tubes (or any tube for that matter) is pretty small.

If we switch our focus to incandescent lamps, an example of a tungsten
filament with which we all have large experience, we could perhaps
extrapolate that anecdotal experience to tubes in general.

If I eliminate the cases where I dropped, or thumped the lamp bulb (trouble
lamps), I cannot remember a case where a household tungsten filament lamp
has failed at other than turn on or turn off.... and since I have spend my
life living with others, I cannot say for certain that those cases where
I thought the bulb must have failed on turn off, weren't actually cases
where it failed at turn on for a house mate, and they didn't take the time
to replace the bulb, or feel the need to tell me about the failure.

If, however, we wish to ditch the anecdotal evidence, there is ample
statistical evidence, compiled by the lamp manufactures, to allow them
to come up with the following equation for tungsten filament lamp life:

[life at test V/life at rated V] = [rated V/test V] ^ 12

Using a 5% reduction in operating voltage, we get:

[life at test V/life at rated V] = [Vr/(Vr(1-0.5))] ^ 12

or,

[life at test V/life at rated V] = [1.05]^12 = 1.85

Which means by simply lowering the lamp's applied voltage by 5% we increase
its life by nearly 2 times!

Which fits very nicely with the wartime conservation recommendations made
by some of the tube manufacturers.

-Chuck Harris

813 warm up time
 

A wrote:

The key issue which is not discussed at all above is that you have to look
at _some_ sample population to see the effect of lower filament voltage on
increased filament life. The question I ask, again, is how many guys out
there with filament cathode power tubes have had filaments blow out
(compared, say, with decrease in power output, or internal shorts that
blow fuses) in some manner that one might hypothesize is due to filament
warmup being too fast. Remember, I had one 813 filament open up on me even
though I was going from zero to ten volts, slowly over about ten seconds,
and on a Chinese 813 about one year old. So, I conclude, on a sample size
of one, that a filament can blow even if you raise filament voltage
slowly. Oh, yes, I also slowly decrease filament voltage to zero, too,
when I shut down the station. And, I'll remind everyone that I've had lots
of amplifiers in my ham career, and with no inrush protection, and never
lost a filament. I'd still like to hear from others about this.

It depends entirely on the application and how the tube fails in that
application. But yes, Varian has done statistical analysis and there is
an Eimac white paper on filament voltages.

Regarding higher filament voltages, I remember as a kid that we had a TV
set where the picture tube cathode emission deteriorated after some years
of use thus causing a weak picture (white areas were gray, gray areas were
black) and they had these little filament voltage boosters that caused the
filament to heat up to hotter temperatures thust restoring cathode
emission for some unknown additional period of time (I think the voltage
boost was from 6.3 vac to maybe 7.5 or so) since a hotter filament should
burn out sooner. Interestingly, we were still using that TV, every night,
for another three years. Again, a sample population of one. However, the
picture brightness did come back to fully normal levels.

Yes, the picture tube brightners will get a little extra life out of a
CRT with poor emission. So will a "CRT Rejuvenator" which will throw
a large reverse voltage on there to blow debris off the cathode.

Surely there are a few people out there who have done some actual
(experimental) playing around with their tubes and can tell some stories
instead of passing on technical rumors.

I suggest getting the Eimac white paper. Or for small signal tubes, a
copy of "Subminiature Electron Tube Life Factors," an NTIA report authored
by some Raytheon folks.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

813 warm up time
 

Nice stories below. Credible. Thanks. I have a few comments below.

On Sun, 6 Apr 2008, COLIN LAMB wrote:

My Collins KWM-2 uses a home brew power supply. Step start on filaments -
at correct voltage and no high voltage for 60 seconds. Same tubes in it for
30 years. I think the only two power amplifier tubes that failed were
dropped on the floor. Some amplifiers adjusted the filament voltage to be
correct and some were never measured.

Out of many dozens of tubes in ham gear, I think I never lost one by any
failure mode. I found an old Halicrafters S-85 at a hamfest and bought it
out of nostalgia. Has original tubes (all marked Halicrafters).

Our B&W TV sets (when I was a kid), however, had maybe half a dozen tubes
go soft and needed replacing. I've bought a number of ac-dc AM/FM radios
with tubes at hamfests and still have original tubes and still work!
Vintage 1950s.

I ran a 3 x 813 amp for years and never changed the tubes or even measured
the filament voltage. Just used a transformer with the rated voltage and
called it good. Unless the filament transformer has a current rating much
higher than the demands of the amplifier tubes, the surge will probably be
ok.

Incidently, the home brew equipment looks practical. I built a vfo using
the Collins 70H3. The problem with it is that it covers 1.5 to 3 MHz with
10 turns. That is 150 kHz per turn. Bad for a linear dial.

Yeah, I know. So, I use gears and don't worry about more than couple kc
accuracy. I'm not a Digital readout freak.

I bought a couple of R-390 VFOs from Fair Radio Sales (Lima, Ohio). Out of
three I bought, two worked and they are something like 2.4 to 3.4 mHz, and
so 100 kc/turn (ten turns nominal, twelve turns real, and still linear,
they go actually up to 3.6 so can use directly on CW part of 80 meters).

I used a 8:1
reduction gear and a crystal controlled mixer to cover 5 to 6.5 MHz, then
limited use to 5 - 5.5 MHz. That was coupled in as the second vfo for my
Drake TR-5, so when I switch it in, the Drake digital dial displays the
frequency. Extremely stable. Oh, I converted it to solid state, also,
which is easy to do. There is one minor problem in that there are no stops
on the dial. Not a problem for me, but if some kid came in and started
twisting, he could break something. Oh well, you need to take some risks in
life.

make your own stops.

73
W4PON

73, Colin K7FM

813 warm up time
 

On Mon, 7 Apr 2008, Chuck Harris wrote:

A wrote:

The key issue which is not discussed at all above is that you have to look
at _some_ sample population to see the effect of lower filament voltage on
increased filament life. The question I ask, again, is how many guys out
there with filament cathode power tubes have had filaments blow out
(compared, say, with decrease in power output, or internal shorts that blow
fuses) in some manner that one might hypothesize is due to filament warmup
being too fast.

If I understand your request, you would like us to abandon the advice of
the tube manufacturers, and instead use our own anecdotal accounts of
tube filament failures?

Yes. The advice of tube manufacturers comes from experience with fairly
large populations of tubes and what is wrong with us all just actualy
talking about our own actual experience (like I did)?

It is unlikely that any of us have run herd on as large a sample set of
tubes as the manufacturers did.

But a lot of us old timer-types surely had--just like me--several
amplifiers running 2-3-4 tubes in parallele, and for years, and that
starts to add up to a population of 10-20 tubes (at least for me). Not
large, but enough.

Clearly the chance of filament failure
among transmitting tubes (or any tube for that matter) is pretty small.

As I've said before, "chance" is speculative. Out of all of my hamming and
SWLing, I have heard very little on guys turning on their amplifiers and
discovering a tube that didnt' light up. I've heard more stories of guys
smoking their little metal-ceramic forced-air cooled tubes from
overdriving their grids, or "pushing" tubes, or using sweep tubes (I've
had a couple from hamfests where there was hardly any emission left) that
were maybe not tuned up fast enough, or whatever.

If we switch our focus to incandescent lamps, an example of a tungsten
filament with which we all have large experience, we could perhaps
extrapolate that anecdotal experience to tubes in general.

If I eliminate the cases where I dropped, or thumped the lamp bulb (trouble
lamps), I cannot remember a case where a household tungsten filament lamp
has failed at other than turn on or turn off....

Agreed. I've had a few flicker a bit and then a few light turn-ons
later...poof and it goes out.

and since I have spend my
life living with others, I cannot say for certain that those cases where
I thought the bulb must have failed on turn off, weren't actually cases
where it failed at turn on for a house mate, and they didn't take the time
to replace the bulb, or feel the need to tell me about the failure.

If, however, we wish to ditch the anecdotal evidence, there is ample
statistical evidence, compiled by the lamp manufactures, to allow them
to come up with the following equation for tungsten filament lamp life:

[life at test V/life at rated V] = [rated V/test V] ^ 12

Using a 5% reduction in operating voltage, we get:

[life at test V/life at rated V] = [Vr/(Vr(1-0.5))] ^ 12

or,

[life at test V/life at rated V] = [1.05]^12 = 1.85

Which means by simply lowering the lamp's applied voltage by 5% we increase
its life by nearly 2 times!

Yes, and sometimes it is worth doing this. I'll bet that the long life
bulbs out there are made with a little more filament wire so the
temperature is maybe (also) 5% lower, too.

Which fits very nicely with the wartime conservation recommendations made
by some of the tube manufacturers.

Fine.

-Chuck Harris

813 warm up time
 

A wrote:


Which means by simply lowering the lamp's applied voltage by 5% we
increase
its life by nearly 2 times!

Yes, and sometimes it is worth doing this. I'll bet that the long life
bulbs out there are made with a little more filament wire so the
temperature is maybe (also) 5% lower, too.

Which fits very nicely with the wartime conservation recommendations made
by some of the tube manufacturers.

Fine.

Now, the second part of the question is: does it matter?

If the filament life under normal operating voltages exceeds 20,000 hours,
than dropping 5% and gaining an additional 18,000 hours, is probably
not going to result in a noticeable improvement in life. Forever is
forever.

-Chuck Harris

813 warm up time
 

On Mon, 7 Apr 2008, Chuck Harris wrote:

A wrote:


Which means by simply lowering the lamp's applied voltage by 5% we
increase
its life by nearly 2 times!

Yes, and sometimes it is worth doing this. I'll bet that the long life
bulbs out there are made with a little more filament wire so the
temperature is maybe (also) 5% lower, too.

Which fits very nicely with the wartime conservation recommendations made
by some of the tube manufacturers.

Fine.

Now, the second part of the question is: does it matter?

If the filament life under normal operating voltages exceeds 20,000 hours,
than dropping 5% and gaining an additional 18,000 hours, is probably
not going to result in a noticeable improvement in life. Forever is
forever.

FYI, FWIW...

Well, that is, kinda, why I was trying to bring the discussion FROM the
"manufacturers recommendations" (on large populations) TO what is everyone
noticing from their own (multiple) amplifier experiences and what everyone
else yaks about in terms of their own (multiple experiences) with filament
power tube lifetimes.

Yeah...20,000 hours is a whole lot of ragchewing. I think I never in my
life spent more than about 10-15 hours/week with amp filaments lit up.
Today, I have the 813 filaments on about 2 hours a week (and drive the
pair with a single 811 in gg and it's filament is on, also, and not
not voltage managed, either). And, I've never blown an 811 filament, ever,
and I had a few of those tubes in amplifiers, too.

FYI, FWIW

-Chuck Harris

813 warm up time
 

A wrote:

Now, the second part of the question is: does it matter?

If the filament life under normal operating voltages exceeds 20,000
hours,
than dropping 5% and gaining an additional 18,000 hours, is probably
not going to result in a noticeable improvement in life. Forever is
forever.

FYI, FWIW...

Well, that is, kinda, why I was trying to bring the discussion FROM the
"manufacturers recommendations" (on large populations) TO what is
everyone noticing from their own (multiple) amplifier experiences and
what everyone else yaks about in terms of their own (multiple
experiences) with filament power tube lifetimes.

Yeah...20,000 hours is a whole lot of ragchewing. I think I never in my
life spent more than about 10-15 hours/week with amp filaments lit up.
Today, I have the 813 filaments on about 2 hours a week (and drive the
pair with a single 811 in gg and it's filament is on, also, and not not
voltage managed, either). And, I've never blown an 811 filament, ever,
and I had a few of those tubes in amplifiers, too.

FYI, FWIW

If we extend the universe of tubes observed to the TV and radio types, I
would have to say that it is very rare for me to find a burned out filament
in the 6.3 and 12V tubes. And very common in the very delicate 35-75V tubes
used in series string sets.

-Chuck

813 warm up time
 

On Tue, 8 Apr 2008, Chuck Harris wrote:

A wrote:

Now, the second part of the question is: does it matter?

If the filament life under normal operating voltages exceeds 20,000 hours,
than dropping 5% and gaining an additional 18,000 hours, is probably
not going to result in a noticeable improvement in life. Forever is
forever.

FYI, FWIW...

Well, that is, kinda, why I was trying to bring the discussion FROM the
"manufacturers recommendations" (on large populations) TO what is everyone
noticing from their own (multiple) amplifier experiences and what everyone
else yaks about in terms of their own (multiple experiences) with filament
power tube lifetimes.

Yeah...20,000 hours is a whole lot of ragchewing. I think I never in my
life spent more than about 10-15 hours/week with amp filaments lit up.
Today, I have the 813 filaments on about 2 hours a week (and drive the pair
with a single 811 in gg and it's filament is on, also, and not not voltage
managed, either). And, I've never blown an 811 filament, ever, and I had a
few of those tubes in amplifiers, too.

FYI, FWIW

If we extend the universe of tubes observed to the TV and radio types, I
would have to say that it is very rare for me to find a burned out filament
in the 6.3 and 12V tubes. And very common in the very delicate 35-75V tubes
used in series string sets.

-Chuck


Well, my comparable experience is the ac/dc AM/FM radios (12 v and 35 v
tubes) and in another post I mentioned buying up a number of them at a
couple of hamfests (and a thrift store) and finding that they all still
worked AND had the original tubes (marked with same brand as brand of
radio) in them.

But, the series string strategy was obviously the "cheap" way for
manufacturers to save on the price of a power transformer AND any
irregularities in the filament mechanical tollerance contributed to early
failure, which, of course, contributed to pressure on the consumer to buy
a whole new TV or radio, thus contributing to the nation's economy (if you
get my drift).

813 warm up time
 

A wrote:


If we extend the universe of tubes observed to the TV and radio types, I
would have to say that it is very rare for me to find a burned out
filament
in the 6.3 and 12V tubes. And very common in the very delicate 35-75V
tubes
used in series string sets.

-Chuck


Well, my comparable experience is the ac/dc AM/FM radios (12 v and 35 v
tubes) and in another post I mentioned buying up a number of them at a
couple of hamfests (and a thrift store) and finding that they all still
worked AND had the original tubes (marked with same brand as brand of
radio) in them.

It can happen, but probably your good luck was the result of the radio
not seeing much use. Does it show signs of obvious use?

The 35 - 117V tubes have a large hank of zig-zagged very thin wire
as their heater. The wires come to a sharp V which isn't a good
idea. I have almost never found a 50V tube that was good.

But, the series string strategy was obviously the "cheap" way for
manufacturers to save on the price of a power transformer AND any
irregularities in the filament mechanical tollerance contributed to
early failure, which, of course, contributed to pressure on the consumer
to buy a whole new TV or radio, thus contributing to the nation's
economy (if you get my drift).

The AA5 tube lineup was definitely an economizing move that could only
happen in the US. At one point, GE put everything in two tubes: one compactron,
and one rectifier/audio output tube...if I recall correctly.

-Chuck

813 warm up time
 

On Wed, 9 Apr 2008, Chuck Harris wrote:

A wrote:


If we extend the universe of tubes observed to the TV and radio types, I
would have to say that it is very rare for me to find a burned out
filament
in the 6.3 and 12V tubes. And very common in the very delicate 35-75V
tubes
used in series string sets.

-Chuck


Well, my comparable experience is the ac/dc AM/FM radios (12 v and 35 v
tubes) and in another post I mentioned buying up a number of them at a
couple of hamfests (and a thrift store) and finding that they all still
worked AND had the original tubes (marked with same brand as brand of
radio) in them.

It can happen, but probably your good luck was the result of the radio
not seeing much use. Does it show signs of obvious use?

Lots of dust, but looks mainly like there was never much moisture present.
However, I have one old Zenith with lots and lots of wear on the knobs,
loosness to the knobes-shafts, and it has all the original tubes, too.

But, by the way, I've had a lot of tube/transformer as well as ac-dc
radios and never had a tube blow out. Yeah, I know, it can be luck.
Certainly it was different with tube TV sets wev'e had where we had to
replace a tube every six onths because of brightness/constrast weakness,
or vertical/horizontal roll, etc., problems.

The 35 - 117V tubes have a large hank of zig-zagged very thin wire
as their heater. The wires come to a sharp V which isn't a good
idea. I have almost never found a 50V tube that was good.

Well, my experience was different.

But, the series string strategy was obviously the "cheap" way for
manufacturers to save on the price of a power transformer AND any
irregularities in the filament mechanical tollerance contributed to early
failure, which, of course, contributed to pressure on the consumer to buy a
whole new TV or radio, thus contributing to the nation's economy (if you
get my drift).

The AA5 tube lineup was definitely an economizing move that could only
happen in the US. At one point, GE put everything in two tubes: one
compactron,
and one rectifier/audio output tube...if I recall correctly.

Yeah, and I was a little bit against that for the reason that if you had
three functions in a tube and one blew out, you had to replace the whole
tube. Probably cheaper to manufacture, but I never looked up the prices on
the compactrons vs one/two function tubes, do you recall any?

Also, its harder to find compactron sockets and they seem smaller spacing,
so harder to repair.

FWIW, I'm phasing out of miniature tubes in favor of
octals because they are much easier to work with, solder, put VOM probes
on, and with octal keys easier to put into sockets and take out of
sockets, and I thing the glass envelope should be a little cooler since
comparable heat is dissipated over a larger surface area.

Thanks for your comments.

-Chuck