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OT: expensive decorative lamps that won't light, for no obvious reason

A few months back I got around to cleaning my condo's ceiling fixtures. These use tiny bulbs with miniature Edison bases. Some had burned out.

Some bulbs had behaved oddly, going "dead", but responding to being tightened. So I decided to examine all the non-lighting bulbs closely.

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All but one were burned out. The other showed no visible filament break, but my ohmeter said "open". I put it aside and tried periodically to fix it. (These lamps cost about a dollar apiece.) Though I unsoldered and resoldered the base and thread connections -- and confirmed there really were wires going to them -- there were no visible signs of damage.

This morning I gave one last shot. This time I twisted off the brass base, this action apparently pulling out the broken part of the wire going to the tip.

Using a magnifier, I could see that wire "ending" about halfway along the internal glass stem. It appears the wire had (or developed) a high-resistance section, which burned open the wire.

The same thing happened to the bottom Calrod unit in my oven several years back, so I shouldn't have been surprised.

PS: I have plenty of things to keep my busy, but I enjoy Show and Tell.

Reply to
William Sommerwerck
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Looks like you are describing the lamp's fuse?

Grant.

Reply to
Grant

I didn't know they had them. I assumed it was a sample defect.

Reply to
William Sommerwerck

I thought I recalled seeing something about there being a weak spot intentionally added to the internal leads in case the filament shorted inside the bulb...

Can't find anything in quick online searches though, and I don't have a line voltage light bulb design specs book.

John :-#(#

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(Please post followups or tech inquiries to the newsgroup) 
John's  Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9 
(604)872-5757 or Fax 872-2010 (Pinballs, Jukes, Video Games) 
                      www.flippers.com 
        "Old pinballers never die, they just flip out."
Reply to
John Robertson

Here you go. Scroll down to "Why burnout is sometimes so spectacular". (I'm awfully good at finding stuff.) This bulb obviously had a defective fuse. You learn something new every day.

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Reply to
William Sommerwerck

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- for the lazy.

Thanks!

Gee, an Internet light bulb database, who'd have guessed (OK, I should have known better), and why didn't the search engines turn that up in my earlier searches?

John :-#)#

--
(Please post followups or tech inquiries to the newsgroup) 
John's  Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9 
(604)872-5757 or Fax 872-2010 (Pinballs, Jukes, Video Games) 
                      www.flippers.com 
        "Old pinballers never die, they just flip out."
Reply to
John Robertson

I Googled "incandescent lamp internal fuse". It was #4, rising with a bullet.

Reply to
William Sommerwerck

Hmm, I didn't use 'incandescent', but putting that in (I used just lamp) I found some interesting reading for "incandescent lamp lead fuse" - one from some retired electricians writing in 1922 about early shipboard lighting where fuses hadn't been considered...almost set the ship on fire!

Fourth down titled: Electric Fuses - Page 4 - Google Books Result

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or a tiny custom URL:

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John :-#)#

--
(Please post followups or tech inquiries to the newsgroup) 
John's  Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9 
(604)872-5757 or Fax 872-2010 (Pinballs, Jukes, Video Games) 
                      www.flippers.com 
        "Old pinballers never die, they just flip out."
Reply to
John Robertson

I repair donated for recycling incandescent miniature Christmas lights and donate to the local Goodwill. A couple of strings that I have gotten have every single miniature light bulb burned out. Apparently the owner/user ne ver replaced the burned out bulbs, and as the voltage across the lit bulbs increased due to the shunts on the filaments of the burned-out bulbs, there was an escalating burn-out. It must have made a spectacular flash at the final failure.

Reply to
hrhofmann

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