Bad Bulbs?

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Lenp
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Bad Bulbs?

Post by Lenp » Sat Sep 15, 2012 6:39 am

Here's an odd issue I am dealing with...

I have a 3 lamp coach light style fixture on a post by the walkway and it is fitted with Sylvania 60W flame tipped lamps.
Since we don't need a lot of harsh light I have a diode in line to drop the wattage to a softer glow and all the other outside incandescent fixtures are also diode equipped. The bulbs in this fixture are failing constantly. They crack, and of course they blacken as the filament consumes itself. At first I suspected a water leak and checked the fixture tops, even spraying the underside with an undercoating spray in case I missed a leak. These bulbs last about 3 weeks then in a few days all three have failed. The cracks are around the midsection of the glass. In some cases it is a hairline crack and in others the lamp is in pieces. I am suspecting the Sylvania lamps and may even send the blown ones to them, but the question, why just this fixture? All the outside lights are on the same circuit, and operate off the same controls.

Theories anyone?
Len

“To invent, you need a good imagination and a big pile of junk.” (T. Edison)
"I must be on the way to success since I already have the junk". (Me)

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dacflyer
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Re: Bad Bulbs?

Post by dacflyer » Sat Sep 15, 2012 7:34 am

are there other lamps that use the same bulbs and diode like this one ?

have you tried it for a while without the diode ? same results ?
if not same results, i am wondering if the bulbs cannot tolerate the 1/2 cycle if the diode.
have you tried another brand of bulbs ? results ?
is the lamp fixture able to breath ok ( no heat issues ) i know them type of bulbs do generate a lot of heat. then again as the bulb cracks, i wonder if that is not a thermal shock issue,..
are the bulbs fogged up when they crack or just cracked ? (cracked when they were on , or were they shattered?

just some ideas to ponder...
you said it is a post lamp ? is vibration a possible issue ? wind or otherwise?

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Janitor Tzap
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Re: Bad Bulbs?

Post by Janitor Tzap » Sat Sep 15, 2012 11:01 am

That does sound strange.

But I think Dac could be on the right track,
in that the light bulbs are getting thermally shocked,
during the initial turning on of power.

The diode(s) may not be rated high enough for that string of light sockets.
Thus, the bulbs receive the current spike at the initial turning on of power,
due too the diode(s) have to low a Voltage & Current rating.

Do you have large trucks, buses, a lot of traffic driving by your home?
The vibration of vehicles passing close by could over stress the bulbs.

If you are bound and determined to have lights on your walk way.
Switch out the incandescent bulbs for some LED lights instead.


Signed: Janitor Tzap

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Bob Scott
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Re: Bad Bulbs?

Post by Bob Scott » Sat Sep 15, 2012 7:36 pm

I suspect that you have those fixtures sealed so well that condensation forms inside the fixture at night while the lamp is off. Vent it so air can flow from bottom to top but have a hood so that water can't get in.
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Re: Bad Bulbs?

Post by gerty » Sat Sep 15, 2012 8:43 pm

Another alternative, if you have access to do it, wire all three bulbs in series. That'll give you the dim light, and lower the voltage to the bulbs.

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Re: Bad Bulbs?

Post by Dean Huster » Sun Sep 16, 2012 3:10 pm

.... condensation forms inside the fixture at night while the lamp is off.
I find that in the odd world where I live, most of my outdoor lamps are off during the day (I guess we use the sun a lot more here); at night, the lamp is on and would chase moisture away.
Dean Huster, Electronics Curmudgeon
Contributing Editor emeritus, "Q & A", of the former "Poptronics" magazine (formerly "Popular Electronics" and "Electronics Now" magazines).

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dacflyer
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Re: Bad Bulbs?

Post by dacflyer » Sun Sep 16, 2012 8:02 pm

another idea to try... use a lamp dimmer instead, you can conceal it in the post of the post lamp..
set it to desired level 1st..

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Lenp
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Re: Bad Bulbs?

Post by Lenp » Mon Sep 17, 2012 6:13 am

Thanks all for the comments!
I do not feel the diodes are any part of this issue. I have used diodes in control panel lamps for years and the lamp life is extended many times, not shortened. If it did affect the lamp, the filament would be damaged. Also, If the diode would short, the lamp would just see the full voltage, as if it were operated without the diode. A dimmer, would also lower the average voltage like a diode, providing an adjustment that is really unneeded.

I believe that heat is not an issue since now the weather has cooled and with the diodes the lamps also run cooler. In any case the temperature is below the value that a lamp without a diode would create. Without a diode the inrush current would be larger, the thermal stress larger and that is contrary to the problem.

As for moisture, there has been no rain for quite some time and another lamp just went out, the same way, Condensation is also possible but I would think it would accumulate on the fixture glass before the lamp.

Wind vibration is minimal and other vibrations are rare since it is a rural setting. (Except for recent earthquakes in the East :smile: )

I would think that all of these would cause the filament to break, not the lamp glass to crack. It is cracking at the widest diameter of the glass, and since the lamps are probably blown into the flame shape, it is also the thinnest. Some of the lamps have a hairline crack, others crack completely around the lamp but none crack at the top as might be expected from water dripping.

I really feel they are defective lamps and I plan to use these lamps until the package is consumed. They will be sent back to Sylvania for their inspection (or trash can) as their policy.
Remember, years ago Sylvania was made famous for their 'Blue Dot Flashbulbs' Maybe these came through mis-marked, and are really time delay no dot flashbulbs! :idea:

SIDE NOTE:
There appears to be some opinion that a lamp operating on DC, with its directional electron flow, causes the filament to be thinner on one end than the other due to filament migration and since AC reverses directions, this effect is not present. I would appreciate seeing any definitive info on this!

Thanks to everyone!

Len
Len

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"I must be on the way to success since I already have the junk". (Me)

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dacflyer
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Re: Bad Bulbs?

Post by dacflyer » Mon Sep 17, 2012 6:03 pm

again i ask did the lamps break while in operation ? (do you see the insides all smoked up?)
did they crack, fog up and go out?
or crack after they were turned off ? you mentioned the filaments turned black as they consumed their self. if a bulbs pops when in. it smokes up..

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Bob Scott
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Re: Bad Bulbs?

Post by Bob Scott » Mon Sep 17, 2012 6:43 pm

Dean Huster wrote:
.... condensation forms inside the fixture at night while the lamp is off.
I find that in the odd world where I live, most of my outdoor lamps are off during the day (I guess we use the sun a lot more here); at night, the lamp is on and would chase moisture away.
In the world in which I live in, in this Pacific Northwest rain forest, if there are no clouds in the clear sky on an autumn evening you can see stars. The great vastness of space is visible and it acts as a giant sink to all heat radiation from the surface of the earth at night. Stuff left outside gets really cold at night with no puffy clouds there to act as blankets, absorb heat radiation and reflect some of it back to keep us warm.

This is why my car is all fogged up on the inside most mornings at this time of year. (It is exposed; no garage or carport.) I have to wipe the windshield and windows with a cloth on the inside in order to see out before the defroster warms up and kicks in. I thought that this effect might be how moisture is getting inside the fixture. It's just a suggestion, Dean.

Then again, the problem night just be that the bulbs are made in China with glass made out of any closest available melted-down sand. You'd be surprised at how many of my suggestions are wrong!
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Lenp
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Re: Bad Bulbs?

Post by Lenp » Tue Sep 18, 2012 6:40 am

dacflyer,
Yes.. I mentioned in my first post the lamps appear to crack during operation and the insides are all blackened. Some have hirline cracks, some are in pieces.

Bob,
Through my sunglasses, It is surprising to see how many residences and car lots around here still have their outside lights on all day long!
Len
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dacflyer
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Re: Bad Bulbs?

Post by dacflyer » Tue Sep 18, 2012 12:30 pm

ok, i just wanted to make sure i understood it right..

if the bulbs crack and the insides are black, then you can be certain they did not crack while they were on, otherwise the bulb would have been all smoked up on the inside, (white fog/smoke)

i have heard stories of bulbs soot when they were under powered. for some reason it caused soot to build up in the bulb.. in some theatrical bulbs they actually had sand in the bulbs, so that periodically the bulb could be removed and the sand could be shook around in the bulb to clean the soot off the glass. this had to be done otherwise the bulb would overheat and thus the glass would crack or the bulb would pop from the thermal stress after the light was turned off.

have you tried to see how the bulb last when used at full power ?
i think your problem is more like described above..
if i was you, i'd try a different brand or maybe try using some of the new halogen type bulbs..

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MrAl
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Re: Bad Bulbs?

Post by MrAl » Thu Sep 20, 2012 2:06 am

Hi Len,

Glass cracks easy when there is a large enough temperature differential across parts of the glass piece. But this is well known so glass used for certain things like cookware is made from specially formulated glass that can take extra stress like this.

The glass used for bulbs can take a lot of stress and i've even tested this at one point. Was the manufacturer different than the one you are dealing with? Im sure it was as this was quite a long time ago. But they know bulbs get hot so they would all make the glass similar so that it doesnt crack when the bulb gets hot.

So most likely the bulbs have been somehow modified from the original design. Maybe they found it cheaper to use a different glass and just didnt care about the consequences as long as they still sold bulbs. I say this because it appears that everything else is the same such as bulb fixture and the relative environment.

So a few experiments are in order :smile:

Take a different bulb and heat it with a torch and take a 'bad' bulb and heat it. See how close the torch has to be in order to break the glass. If there is that much difference, it should show up somehow during a test where we can quantify the way it is breaking. Once we have that kind of data we can then say, "Well bulb A broke at a distance of 5 inches and 15 seconds", and bulb B broke at a distance of 7 inches and 20 seconds". Bulb B is better.
This is if you are in the mood to do this and feel like sacrificing a few bulbs here and there.

Otherwise, just try using some of those 'curly' bulbs. They are much better on energy anyway so you'll save money at the same time. LED's would really be nice, but probably a lot more expensive than the curly bulbs. Or at least try one and see how long it lasts.

Some pics of the lamp fixture would be nice to see at this point too just so we can get an idea what kind of enclosure we have here. But if the 'other' bulbs didnt break and only this new set did, that tells us the new set is defective, unless of course something else rather drastic has changed that you didnt notice yet.
Anyone hitting them with a hammer when you're not looking ? :smile:
LEDs vs Bulbs, LEDs are winning.

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Re: Bad Bulbs?

Post by haklesup » Thu Sep 20, 2012 6:04 pm

Its most likly you have a defective package of bulbs but that should be easy enough to confirm with a new pack or a different brand. They may have been dropped in the store or they may have changed the assembly process in such a way that there is a weakened chip ready to turn into a full crack with just a little pressure. Thermal stress may propigate a crack but it should not start one, there had to be an origination site.

I bet the crack is in or under the potting compound in the base. I have seen plenty of bulbs let go of this compound but they often still work until the glass chips because of the loose base.

A catastrophic introduction of air should burn out the filiment quickly but a slow leak could allow it to boil off and plate tungtson over the entire interior of the bulb. The amount of discoloration is a hint to how fast it failed as is the condition of the remaining filiment.

If its not the bulb, the only way I can imagine the fixture is bad is if the threaded socket were tight causing you to use too much force to screw in the bulb thus inducing the crack. Use a thread lube like petrolium jelly.

A third possibility is that counterfeit light bulbs made their way into the store. These can be either authentic but rejected bulbs or copies with inferior materials. Is the bulb or package marked with the country of origin, I bet they are not made in the USA.

I also do not blame the diode, they are well documented to extend the life of incandescents in most cases. Even with the unlikly introduction of 30Hz vibration I think it's highly unlikly to cause glass failure without a preexisting nick or defect..

Call the customer service number on the package and complain the whole pack burned out prematurely, they are likly to either say return them to where you bought them or issue a coupon to buy more. If they did burn out in under a month (or 90 days if you bought them at HD or other big box) you should just return them to the stor you purchased them at for exchange or refund. I'm pretty sure a good brand like Sylvania does have a guarantee beyond what the state requires (store return for defective merchandise)

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Re: Bad Bulbs?

Post by Edd » Thu Sep 20, 2012 8:49 pm

.


Meester Len . . . . .

on . . . . . INCANDESCENT LAMP RELIABILITY :

With 3 lamps in the unit, any possibility of your aesthetically / physically mounting in a fourth, like lamp?

My story:

Back in '75, doubled the width of a " Brick and Mortar " storefront in a strip shopping center by taking in the adjunct . . . then defunct . . .photography store.
That left 1/2 of the 30 ft front with a display window and the possibility of using that plate glassed section for a 15 ft wide display of viewable wares.
Six "oat meal container" styled cylindrical light fixtures were spaced out and their design was using an internal aluminum parabolic reflector which made the use of a common lamp, be functioning as a floodlight type.
Instead of hooking the 6 lamps in the conventional manner, I chose to initially try 2 in series and evaluate the light output.
I found that the use of 100 watt clears was still giving me all of the light needed at night on lighting up the display.
Soooooo, I just went into the frontal crawl space and was about to wire the clusters into the AC supply line.
While up there, I noticed that there was OUR AC supply and about a foot away was conduit and tap off boxes for the feeding of the whole shopping centers frontal signs and sidewalk path lighting.
That was making it HOT at all times, with photocells or timers switching the different loads off or on.
Needless to say, I just moved my AC power source acquisiton, over to the closest junction box on that " FREE " electricity conduit source.
Now I can easily count up that time of use, by the following intervals of 5 year leases, which went from '75--'87.
1987 was the timing of the moving to a newer higher traffic volume location.
At the end of 1987, that end of that strip center of ~14 shops , had that corner torn into in order to build an ELL extension, in adding more shops to the center.
Now in excluding leap years, thats 12 years times 365 days for 4,380 days times 24 hours a day continual run time for a total of 105,120 hours. Not once did I ever have a lamp failure !
Yet, they may have ALL failed, when the demolition dozer hit them.
Seems like I have seen the spec of ~650 hours expected life time for a 60 watt lamp, being written on their packages.
Plus . . . . I have seen miniature lamps manufacturers touting the greatly enhanced reliability of their lamps, (as pilot lamps) when being used at 10% REDUCED supply voltage.


Nowwwwwww . . . . as for initiating a "Beta" testing . . . would you be interested in just taking the unit as is and placing two lamps in series and leaving the SOLE errant lamp still connected thru a series diode.
The series AC connected pair will discount any tungsten depletion and transmigration of being run on a pulsating unidirectional polarity source.
( UNLESS those lamps have already been partially affected by that situation.)

Thasssitttt . . . . .

73's de Edd
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