True of incandescants, not true of CFL's. The CFL's that don't last
long fail because of integral ballast electronics that have been
simplified and cost-reduced to the point that most fail long before
end of tube life. I've done post-mortems on a few of them. It's a
wonder that they ever worked at all.
No, the standard PAR36 incandescent lamps 25 years ago had the same
lumens per watt as the ones on the store shelves today. About 815
lumens for 75 watts for a 2000 hour tated 120 volt bulb. About 750
lumens for a 65 watt bulb.
135 watt bulbs produce less lumens and last longer when operated on
120 volt circuits.
The "5000 hour" "65 watt equivalent" 15 watt Philips compact
flourescent is also 750 lumens when fully warmed up.
The ones that keep failing on me cost me $11.50 each. The other CFLs
I have in the house are mostly about $5 each. ($17.50 for a package of
3) except for the few IKEA units that cost a bit less, but seem to be
standing up reasonably well, even though they are a bit slow to come
up to brightness (but no worse than the $11.50 ones)
A fair number of the first ones I bought never DID work (well, they
lit for about 15 - 30 seconds) - which is why I now only buy the
"better" more expensive units - which still fail too quickly for my
liking.
Also -- consider the voltage creep over the years. Once upon a
time the home power in the USA was 110 VAC, then it stepped up to 115
VAC, then 117 VAC, and now 120 VAC.
Based on this sentence from:
from the "Why making bulbs last longer often does not pay" section of
the page (a little over half way down).
======================================================================
"You may have heard that the life expectancy of a light bulb is
roughly inversely proportional to the 12th or 13th power of the
applied voltage."
======================================================================
And going for the conservative 12th power, I calculate the
following relative life expectancy.
Volts Relative Life
------------------------------
110 100%
115 59%
117 48%
120 35%
So -- for those of us who have lived long enough, there is
adequate explanation for the shorter perceived bulb life just based on
this, and ignoring any conspiracy theories about the light bulb
manufacturers. (Unless you can prove that the bulb manufacturers
prompted the voltage boosts from the power companies. :-)
Enjoy,
DoN.
My AC line can hit 127 volts most days and no, it isn't balance
problem in the neutral. The primary lines in this subdivision are
almost 50 years old, when a 60A service was standard and no one had
electric stoves or air conditioning. Now, the minimum replacement you
can install is 200A. Because of this, the line voltage goes up, when
the demand goes down.
I used to run the projector bulbs at a B&W TV station at around 90
volts to get a couple hundred hour life from 20 hour rated projector
bulbs in a RCA 16 mm film & 35 mm dual drum film chain. They
recommended going no lower than 3% low if you were running color to
maintain proper color correction. Of course, that meant that I had to
increase the gain of the vidicon in the camera. I would juggle the
levels between maximum lamp life, and acceptable background noise in the
video.
That sounds like an excellent place to use one of the old
General Radio motorized Variacs for maintaining constant voltage. (Of
course, they are old enough that they used tubes, not solid state for
the control of the motor, so you have the problem of filament life
still. :-)
A neat trick -- and yes, I can see why it would not work well
with color.
Enjoy,
Don.
We had a 'Stabiline' regulator for the 120 VAC for the control room.
No tubes, but it could adjust the line voltage to as little as .1V
change.
I kept it set around 2 volts to maintain decent regulation without,
replacing the brushes a every couple months.
It was a now 40+ year old version of this:
I had to make sure to use color film to calibrate it. If I didn't,
reds were brighter than everything else. :)
Motor brushes, or the wiper brush on the autotransformer?
O.K. That then would have been from around 1970. IIRC the GR
one was from the mid 1950s, hence the older control design.
These look like a nice update on the original GR design.
[ ... ]
Hmm ... or just treat it as the opposite of the pre Panchromatic
photographic films -- treated red as black. :-)
Enjoy,
DoN.
On the autotransformer. The motor was a servo.
I've never seen the GR version, but I heard they took a lot more
maintenance than the Superior unit.
Luckily, most of the film we ran was either B&W or kinescope crap.
Most were 16 mm prints produced by the networks & syndicators under
agreements made during WW I.I. so there was little variation in film
quality. Old movies in the library were another story. Some were quite
dark, so you hd to crank up the video gain so people could see them.
O.K. An AC servo, then.
Well -- given the time between the design of the two units, that
is not surprising. GR came up with the idea, and the first
implementation. Their main competitor (in the variable autotransformer
world, at least) came up with the improvement.
:-)
Hmm ... in 35mm theater projectors -- how fast did those burn up
the carbons? (And if the projector stalled, how many milliseconds
before it burst into flame. :-)
Enjoy,
DoN.
Once I set it where it needed to be, I didn't touch it for another
year. After that, it was someone else's problem. :)
We only ran 16 mm film. The 35 mm was slides.
I had the base projectionist bugging me once that I couldn't run his
projectors, since I didn't have a license. I smiled and told him that
mine cost more and he couldn't even see them, let alone run them. Then
I reminded him that his school was one week, and the AFRTS broadcast
engineering course was three years so the operator could repair them,
not just run them. Other than rebuilding a shutter, everything was
repaired on site.
I did run an old RCA 16 mm projector at my high school with carbon
arc. It had a safety shutter that was supposed to close if the film
stopped moving. When it worked. A set of carbons barely lasted one
large reel. There was a box of stubs with about 5 minutes left that
were used for testing projector focus, and after cleaning the lens. We
also had a huge carbon arch spotlight that plugged into a 200A 208
outlet. That was about 40 KW available, after IR losses. It had a stop
to keep you from focusing it on too small an area to prevent a fire on
the stage, over 150 feet away.
As you can guess, I rarely ever sat for an assembly when could hit
the projection booth to run sound.
$10ea - last forever bulbs - for about $1 ea thanks
Nope, no heavy door or other cause of vibration.
Too bad. I just changed the back porch CFL, only lasted 21 months
compared to 23 months on the front porch. Since I didn't get 5-7 years,
I might as go back to 2-3 month incandescents.
David
Sample of two lamps, I just changed the back porch light CFL after 21
months. And several CFLs in each, with similar longevity, after many
regular bulbs changed every 2-3 months.
I went from being irritated at how often I had to replace the old bulbs
to marveling at how long the CFLs lasted.
David
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