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Osram Thermal Starter St291

Osram Thermal Starter St291


Osram L140W/20Sa Fluorescent Tube with 4-pin Osram St291 Thermal Starter

20200512_161257.jpg 20200324_182301.jpg youtube_lC25IB5YdjU.jpg youtube_fJ6l96UTyII.jpg

Light Information

Light Information

Manufacturer:Osram
Model Reference:St291
Physical/Production
Factory Location:Germany

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Album name:meganie / Gear
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Date added:Mar 13, 2020
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dor123
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Other loves are computers, office equipment, A/Cs


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Mar 14, 2020 at 12:29 AM Author: dor123
I see here the electrodes preheated, but the bi-metal opened too fast and didn't let the electrodes to reach their optimal temperature thermionic emission.

I"m don't speak English well, and rely on online translating to write in this site.
Please forgive me if my choice of my words looks like offensive, while that isn't my intention.

I only working with the European date format (dd.mm.yyyy).

I lives in Israel, which is a 230-240V, 50hz country.

vytautas_lamps
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My idol is Mylene Farmer, deal with it.


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Apr 08, 2020 at 02:48 PM Author: vytautas_lamps
0:36 the right cathode.. what is wrong with it? A few more inches and it would end up in the middle of the tube.. is it normal?

New lighting technologies is a pity fest everywhere you look. From LEDs that last only for two months, to a never-ending global starvation of t8 fluorescent tubes.
We shall reinforce ourselves with good old full mercury t12s and HIDs made to surpass one's life, and give them all the middle finger ;

Mr. Orthosilicate
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Apr 08, 2020 at 03:06 PM Author: Mr. Orthosilicate
That’s normal. That appears to be a 140w lamp, which has an operating current of 1.5a. This causes the bulb wall temperature to be very high, which normally causes high mercury pressure inside the tube, leading to less emission at the 2537 angstrom line and more visible spectrum radiation, causing efficiency loss. To compensate, the engineers who designed the lamp created a cold spot in the bulb for the mercury to condense, in order to keep the pressure in the optimum range. Originally, this was done via a nipple in the center of the tube, but this was awkward and fragile. As a result, they changed the cold spot to follow the same principle of american VHO lamps, where the cold spot is created by having one electrode farther into the tube than normal to create a colder zone for the mercury to condense, in order to regulate the pressure.

Before this solution existed, we had a t17 diameter bulb in the US. It also ran at 1.5a, but the pressure was kept low by having a large volume and a low bulb wall temperature thanks to its larger diameter. It worked, but the lamp was not very efficient. We created the cold spot idea originally for our 800mA High Output lamps, and it was later applied to the VHO lamps, which also had a neon gas fill mixture.
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meganie8
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Apr 08, 2020 at 03:06 PM Author: meganie
High output T12 tubes have one (or two) longer electrode stem to create a cold spot behind the electrode where the mercury can condense. Otherwise the pressure would get to high due to the incresed power and heat.

http://www.lamptech.co.uk/Spec%20Sheets/D%20FL%20Sylvania%20F48T12-CW-VHO.htm

I'm looking for:
Osram L20W/39
Osram HTI 1500W/60/P50
Philips SOX 180W

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