I know I could just drop 100 bucks or less if I went LED for a new desk lamp but if anyone can help me figure out what's wrong I'd appreciate it. It was also my dad's lamp and he has since passed so it sort of feels like a piece of him in my office, so I admit to some sentimental attachment here. It it were any other lamp, I'd probably have replaced it.

Some time ago the T-4 style bulb died. I can see a filament just floating around broken inside the bulb so I knew it was shot. Up to that time, the lamp worked flawlessly. I'd never had to change the bulb over the course of probably 10 years of ownership, it was original to the lamp. enter image description here

I purchased a package of T4 bulbs from Amazon. The lamp specifies 50W so that is what I ordered. When the bulbs came in I swapped one in and it just did nothing. I thought maybe it was defective so I tried another and another. Nothing. I RMA'd them thinking I'd been juked by a bad batch or a shady merchant. Ordered another pack from a different vendor and this time the bulb filaments glow but the bulb does not light up. enter image description here

This lamp did used to have a sort of "slow burn" to get to full brightness but it seems to be not be getting any brighter as I wait and I'm fearful if there's some kind of mismatch here that the bulb will pop / blow out. The lamp has two brightness settings and I get the same result on both settings except the low is lower red glow.

Label on the bulb packaging says 50W T-4. I have to believe there's something wrong with the lamp? What are the odds I'd gotten two bad batches of T-4 bulbs from totally different vendors?

Am I just ordering the wrong bulbs? (Amazon Product Link)

Thanks for any help / suggestions.

  • 3
    Take this opportunity to get an LED replacement; new ones are almost as good as halogen, but way cooler and they last forever.
    – dandavis
    Jan 16 at 22:41
  • 1
    To clarify what @dandavis said, you can get 12V T4 LED bulbs which are "50W equivalent" (which is means the brightness will be the same as a conventional 50W bulb). They will use less power and run cooler, and your lamp will last for longer. There is a small possibility (unlikely) that they won't work with the transformer (i'm interested in that "slow start" description - might be a dimming effect which doesn't work well with LEDs), but the investment to try is tiny. As they use less power, and emit less heat, you could even get a brighter one (if that was useful).
    – abligh
    Jan 17 at 10:18
  • Frequent failure is a characteristic of incandescent and halogen bulbs. Countless problems is a characteristic of electrical gear bought on Amazon. I know you sunk $100 into Prime, didn't we all... but don't buy electrical gear there, or at least only buy things that ship and sell from amazon.com. And even then, avoid things popular enough to ever be counterfeited, like GFCI receptacles. That's a big problem even with "sold by Amazon" stuff. Jan 17 at 18:54

The bulbs in the link say 120 Volt. Your lamp says use 12V 50W. I think you just got the wrong bulbs.

  • 2
    The label is a little confusing, since it ends with the 120V AC-Only (power to the lamp itself) after slipping in the 12V lamp spec.
    – Ecnerwal
    Jan 17 at 4:24
  • 2
    There's probably a 120V->12V transformer/converter in the lamp base. Feed 120V in, get 12V out.
    – Mast
    Jan 17 at 11:53
  • Wow I did completely overlook that. Thank you
    – rhurlburt
    Jan 18 at 15:17

The answer by izzy most likely describes the problem. If for some reason the newest bulbs don't function, you should:

  • Check the transformer at the base of the lamp. You'll need a voltage meter to check each lead for the correct output.

  • Check the switch for proper voltage flow.

The transformer may be indicating that it's ready to go. If you don't want to replace it, you could order a lower watt bulb which should illuminate brighter (but that's only if the transformer is weak).

  • 1
    I'd be sceptical of trying to compensate a "weak" transformer with using a different bulb. Most mechanisms that would lead to a lowered transformer output voltage could be accompanied by increased internal heating. Trying to keep running after you have determined that the transformer is broken could therefore be a fire hazard.
    – Emil
    Jan 17 at 8:47
  • 1
    There is no reason to believe that the transformer is broken in any way! Or "weak". Transformers don't get tired, sick, or "weak". In fact if it's a low frequency transformer (probably 60Hz in your country), it'll probably last forever. Switch-mode supplies with a high frequency transformer are much lighter and thus cheaper (since they need to contain much less copper and iron) and are more likely to burn out. But they don't get "weak" before they die! Jan 17 at 13:04
  • 1
    Isn't that funny! I just replaced a lamp transformer the other day that when tested for voltage showed a lower output than it was rated for! I guess your mistaken , pal.
    – ojait
    Jan 17 at 14:37
  • @ojait how do you know it wasn’t always like that?
    – Tim
    Jan 18 at 9:21

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