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BIF
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Frustrated with light bulbs under microwave!

Mon Mar 09, 2015 9:21 pm

So it's not a computer problem, but it's driving me nuts and I know there are a lot of electrically experienced gerbils here, so I must ask.

I have an old GE microwave, probably 8 years old or older. It's mounted above the stovetop and it has two T7 appliance bulbs (medium screw socket) underneath, for illuminating the stovetop, which is electric with a glass top. I'm using 25-watt incandescent bulbs, because these are nice and bright enough to see what I'm doing when I'm cooking.

But these T7's keep burning out. Sometimes they last a couple months, other times only a week or two. They don't always burn out at the same time, but often they burn out within two weeks of each other.

What could be happening? Somebody please help me get back to cooking on the stovetop again!

If we can figure this out, then my recently renewed subscription will have ALREADY paid for itself by eliminating a major source of my stress. Thanks in advance...
 
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Re: Frustrated with light bulbs under microwave!

Mon Mar 09, 2015 9:29 pm

Has this always happened or is it a more recent phenomenon?
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Re: Frustrated with light bulbs under microwave!

Mon Mar 09, 2015 9:31 pm

Industrial bulbs tend to burn dimmer but last longer, especially where there's high vibration.


If it were me, I'd look for an LED bulb with the intermediate base, or I'd screw in an intermediate E17 to candelabra E12 adapter and use one of the commonly-available LED bulbs with the E12 candelabra base.
Last edited by JustAnEngineer on Mon Mar 09, 2015 9:32 pm, edited 2 times in total.
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Re: Frustrated with light bulbs under microwave!

Mon Mar 09, 2015 9:31 pm

Well, do you leave them on all the time? I think T7 bulbs have an average lifetime of 2500-3000 hours? (at least from a quick Google search) That's not very long if you leave them on a ton.
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Re: Frustrated with light bulbs under microwave!

Mon Mar 09, 2015 9:44 pm

I always hated changing the bulbs too.

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However, ThinkGeek apparently has a version that will work right in your `puter now!

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Re: Frustrated with light bulbs under microwave!

Mon Mar 09, 2015 9:53 pm

Scorpiuscat wrote:
Has this always happened or is it a more recent phenomenon?


Recent; just began in the last year or 18 months.

JustAnEngineer wrote:
Industrial bulbs tend to burn dimmer but last longer, especially where there's high vibration.


If it were me, I'd look for an LED bulb with the intermediate base, or I'd screw in an intermediate E17 to candelabra E12 adapter and use one of the commonly-available LED bulbs with the E12 candelabra base.


The receptacle is not large enough to accommodate a larger bulb; it's a little glass door fastened by a short phillips screw. But I will investigate your suggestions; thanks!

DancinJack wrote:
Well, do you leave them on all the time? I think T7 bulbs have an average lifetime of 2500-3000 hours? (at least from a quick Google search) That's not very long if you leave them on a ton.


I sometimes leave them on "dim" at night. But 2500 hours is 104 days; more than 3 months. I'm prepared to change them every 3 months, sure. But these aren't even lasting a week in some cases.

LoneWolf15 wrote:
I always hated changing the bulbs too.


Haha, that's AMAZING! Thank you for the laugh. :lol:
 
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Re: Frustrated with light bulbs under microwave!

Mon Mar 09, 2015 11:02 pm

BIF wrote:
Scorpiuscat wrote:
Has this always happened or is it a more recent phenomenon?


Recent; just began in the last year or 18 months.


OK, so that means something changed.

Either the light bulbs that you are now buying have changed and cannot tolerate that environment like they use too or something in the stove itself changed, for example, maybe the voltage or amps fed to the bulbs changed to something to high for the rated bulbs that you are using and that is why they are burning out prematurely.

Are there higher rated bulbs that you can try just to see if they last longer?
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Re: Frustrated with light bulbs under microwave!

Mon Mar 09, 2015 11:18 pm

If you can cut power to the fixture, I would check to see if the tab\contact on the inside of the socket has been pushed in too far.

If you overtighten light bulbs you can push the contact inward in such a way that there may be some arcing going on in there, which will cause the bulb to burn out sooner. You might even be able to see pits\burns on the contact on the bulb as well as the one in the socket.

We recently had to fix this problem at my mother's house in a standard sized ceiling light fixture. We cut the power to that circuit, tested it, inspected the tab, it had obviously been arcing and was depressed, so we pulled it out about 1/4 inch with pliers, put the bulb back in without over tightening and it has been fine ever since.
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Re: Frustrated with light bulbs under microwave!

Wed Mar 11, 2015 9:32 am

BIF wrote:
So it's not a computer problem, but it's driving me nuts and I know there are a lot of electrically experienced gerbils here, so I must ask.

I have an old GE microwave, probably 8 years old or older. It's mounted above the stovetop and it has two T7 appliance bulbs (medium screw socket) underneath, for illuminating the stovetop, which is electric with a glass top. I'm using 25-watt incandescent bulbs, because these are nice and bright enough to see what I'm doing when I'm cooking.

But these T7's keep burning out. Sometimes they last a couple months, other times only a week or two. They don't always burn out at the same time, but often they burn out within two weeks of each other.

What could be happening? Somebody please help me get back to cooking on the stovetop again!

If we can figure this out, then my recently renewed subscription will have ALREADY paid for itself by eliminating a major source of my stress. Thanks in advance...

Bulbs mounted under microwave... I'd say vibrations from the fan are shaking the filaments while they are hot.
LED bulbs would be an option.
 
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Re: Frustrated with light bulbs under microwave!

Wed Mar 11, 2015 7:19 pm

As mentioned by others, the two most obvious reasons a bulb keeps blowing are:

1) Too much current caused by an arcing contact or a fault in the microwave's power delivery to the light fittings
2) vibration of the filament whilst it's hot.

You can diagnose vibration quite easily by feeling for vibrations on the underside of the microwave. Arcing leaves pitting, scarring or even charring on the connectors so look for that. If you can feel neither vibration nor see evidence of arcing it's time to dismantle the microwave and examine the power delivery route to those lights for faults.

I'd be loathe to spend money on LED bulbs if there's an electrical fault causing them, but LED's are a great solution if the appliance is vibrating.
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Re: Frustrated with light bulbs under microwave!

Wed Mar 11, 2015 8:43 pm

LoneWolf15 wrote:
However, ThinkGeek apparently has a version that will work right in your `puter now!

Image



LOL!

You gotta post that in whm's 850W PSU thread.
 
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Re: Frustrated with light bulbs under microwave!

Wed Mar 11, 2015 10:07 pm

Are these "appliance bulbs" the type used inside ovens ?
Probably not as those are mostly 15 watt..
If you can get that quality in 25 watt try them............

Definitely check your sockets for arcing as others have suggested
 
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Re: Frustrated with light bulbs under microwave!

Wed Mar 11, 2015 10:39 pm

HERETIC wrote:
Definitely check your sockets for arcing as others have suggested

Especially for lamps right over the stove top. I also have a "over-stove" microwave that claims to have a vent fan to suck greasy air out. It makes fan-like noises, but the grease remains in the lamp sockets (it's been 5-6 years since I've tried to rehab mind) and over most of the kitchen.

If you really want to move grease outside, SWMBO is just going to have to live with a commercial kitchen vent hood and fan. I lost that debate, so I spend a day every month cleaning grease out of the kitchen.
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Re: Frustrated with light bulbs under microwave!

Wed Mar 21, 2018 1:26 pm

I bought some dimmable LED T7/E17 type bulbs, 6W and now I think I can see the problem. There is always current being sent to the bulb, so it burns out prematurely. The LED converts that urrent into light so even when the light switch is in the off position, the LED bulb is still glowing.
 
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Re: Frustrated with light bulbs under microwave!

Wed Mar 21, 2018 1:38 pm

schwinn wrote:
I bought some dimmable LED T7/E17 type bulbs, 6W and now I think I can see the problem. There is always current being sent to the bulb, so it burns out prematurely. The LED converts that urrent into light so even when the light switch is in the off position, the LED bulb is still glowing.

If there is current still flowing when the switch is in the "off" position then the switch is defective and needs to be replaced.
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Re: Frustrated with light bulbs under microwave!

Wed Mar 21, 2018 2:25 pm

All my microwaves have gone through bulbs faster than I would like. I just ordered some cheapo LED replacements off Amazon and that's worked well for me.
 
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Re: Frustrated with light bulbs under microwave!

Wed Mar 21, 2018 3:15 pm

just brew it! wrote:
schwinn wrote:
I bought some dimmable LED T7/E17 type bulbs, 6W and now I think I can see the problem. There is always current being sent to the bulb, so it burns out prematurely. The LED converts that urrent into light so even when the light switch is in the off position, the LED bulb is still glowing.

If there is current still flowing when the switch is in the "off" position then the switch is defective and needs to be replaced.

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Re: Frustrated with light bulbs under microwave!

Thu Mar 22, 2018 10:03 am

Do the bulbs burn out when the microwave is started? (power surge to the bulb caused by an ageing component inside the microwave) Or do they just randomly die for no apparent reason, even when the microwave isn't being used.
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