Speaking of light bulbs

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.

If we get a week of run time befire they burn out, we'll buy another one next week.

Isn't that what it's all about now?

Unmarked transistors, Chinese 85° C electrolytics and other floor sweepings are common. :(

Welcome to the 21st Cenuary

That was first take when I opened up one for the first time. :-) ...lew...

I've had better luck with name brand CFL's. They cost more than a buck, but they're holding up well.

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