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

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

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

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).

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

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