Under Cabinet Puck lights rapid burn out

[Npstewart]

I have some under cabinet puck lights with Bi-Pin G8 Halogen bulbs controlled via touch pad tri-level dimmer. The problem I have is that the bulbs tend to burn out about every 2 months, and the other day they all burned out at one time. I am almost positive there is something wrong either with voltage spikes or something down the line. Does anyone have any suggestions? These bulbs are almost $4.00 each!

Thanks Guys

 

[charlie b]

Did you wear cotton gloves when you replaced the bulbs? Contact with human skin will leave oils on the bulb, which will cause early failures.

 

[Npstewart]

Good point, I used a paper towel, perhaps I should be more careful with that and use the gloves.

 

[G._S._Ohm]

the other day they all burned out at one time.

Kinda' sounds like a voltage spike, maybe on top of a slight and sustained overvoltage. Life is proportional to voltage to the 12th power so 10% over gives 1/3rd or less of normal life.

Service lifetime is a few thousand hours and on dimmers it should be very long, but I could not find a link showing how much life reduction would be due to finger oils causing hot spots or etching the glass. I'd think a glass failure would show bulb darkening.

Overvoltage failure symptoms may be a hairline crack or a small melted area in the filament - dunno' fer sure. Given a hairline crack in a fuse, though, I'd say it's a fatigue failure.

 

[Dennis Alwon]

Are these LV pucks? How many on the trany. Some tranies have a minimum wattage and will often not light all the bulbs if you are under the req. wattage.

I don't think it will burn the bulbs out but maybe they weren't burned out???? Tissues with the aloe or whatever in them may be an issue but I doubt paper towels.

 

[G._S._Ohm]

Forgot.
If the tranny is not loaded with the recommended number of lamps then the voltage will be higher than the spec. value due to poor regulation and so the bulbs will burn out quickly.

12 vac outside lights from HD have this, and nowhere does it say to use all the bulbs.
With only 6 out of 10 bulbs the voltage I measured was considerably over the bulb rated voltage value.

 

[Electric-Light]

Can you see the beam dancing around when you close the cabinet? Could be that filament is not well supported and the banging the cabinet door close is shakin' up the filament good.

 

[broadgage]

The cheaper types of halogen lamp only have a life of about 1,000 hours at nominal voltage.
If over run a bit, I would regard a couple of months as a fair life.
With a copper/iron transformer the secondary voltage will increase at less than full load, that combined with a generous utility voltage could give 13 volts on 12 volt lamps and result in only a few hundred hours life.

 

[Dennis Alwon]

I had a customer who called me about the same thing. It turned out she replaced the puck bulbs with 20 watt bulbs. The puck fixture was rated for 10 watts.

 

[Electric-Light]

How are the "12v" indoor lamps rated? Automotive 12v lamps are rated for output at 12.6v or 12v, but the life is rated at 14v, because that is the system voltage with the engine running.