Author Topic: Old reading about the isothermal lamp shape  (Read 1001 times)
Olav
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Old reading about the isothermal lamp shape « on: March 23, 2021, 03:49:10 PM » Author: Olav
Hello @ all,

I found interesting information about the isothermal lamp shape in the 1946 book "Electric Discharge Lamps" by H. Cotton.
The pictures are very small now. That wasn't my decision.
Please click on the picture for a larger resolution.

Here are the pages from the book:


Source: Electric Discharge Lamps by H. Cotton, London 1946


Source: Electric Discharge Lamps by H. Cotton, London 1946


Source: Electric Discharge Lamps by H. Cotton, London 1946


Source: Electric Discharge Lamps by H. Cotton, London 1946


Source: Electric Discharge Lamps by H. Cotton, London 1946


Greetings from Hamburg

Olav
« Last Edit: April 18, 2021, 03:27:50 PM by Olav » Logged
Andy
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Re: Old reading about the isothermal lamp shape « Reply #1 on: March 24, 2021, 02:49:06 PM » Author: Andy
Thanks for uploading this extract Olav.
I love the shape of isothermal lamps, it's just a shame they are not very common.
I'm a bit confused with the temperature scale alongside the illustration of the lamp as I would have thought that the temperatures would be higher closer to the arc tube rather than further away but perhaps there is a reason for this that I am overlooking.
 
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Re: Old reading about the isothermal lamp shape « Reply #2 on: March 24, 2021, 05:26:59 PM » Author: Olav
Hello Andy,

thanks for your answer. I have only one guess: I assume that the proportions in the drawing are correct.
The arctube is almost as big as the base. For me this is almost a medium pressure lamp. I'm not an expert, it's just a guess.
That would be an explanation for the slightly lower temperatures.

Greetings from Hamburg

Olav
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Re: Old reading about the isothermal lamp shape « Reply #3 on: March 25, 2021, 01:01:23 PM » Author: magslight
@Andy: I see it that way that the lamp is in use with socket up and inside due the shape the heat has enough space to circulate. Was there a guideline how to operate them?
@Olav: At page 354 is written the 80 and 125W lamps are operating at 5 to 10 atmospheres and the 400W has a lower pressure so a way bigger arc tube. The 400W is a medium pressure lamp so far I read it. For us Germans is a medium pressure mercury lamp with coating completely unknown as after the war our luminaires got instead a complicate coated medium Hg lamp, just a light bulb for color correction with the standard clear HgH lamp.
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Re: Old reading about the isothermal lamp shape « Reply #4 on: March 25, 2021, 03:18:58 PM » Author: Andy
Hello Andy,

thanks for your answer. I have only one guess: I assume that the proportions in the drawing are correct.
The arctube is almost as big as the base. For me this is almost a medium pressure lamp. I'm not an expert, it's just a guess.
That would be an explanation for the slightly lower temperatures.

Greetings from Hamburg

Olav

The proportions of the lamp in the drawing are certainly accurate.
The bit that puzzles me is that I would expect the scale of 100 to 200 degress centigrade to read in the opposite direction as I would have thought that the temperature was hotter closer to the arc tube.


@Andy: I see it that way that the lamp is in use with socket up and inside due the shape the heat has enough space to circulate. Was there a guideline how to operate them?
@Olav: At page 354 is written the 80 and 125W lamps are operating at 5 to 10 atmospheres and the 400W has a lower pressure so a way bigger arc tube. The 400W is a medium pressure lamp so far I read it. For us Germans is a medium pressure mercury lamp with coating completely unknown as after the war our luminaires got instead a complicate coated medium Hg lamp, just a light bulb for color correction with the standard clear HgH lamp.

Yes The lamp is to be lit with the socket up in the vertical position.
It is a medium pressure mercury lamp with small addition of cadmium in the arc tube. The type is MAF/V and operates on a regular 400W 3.25A mercury ballast.
James has a detailed description of the lamp: http://www.lamptech.co.uk/Spec%20Sheets/D%20MA%20GEC%20MAF400.htm   
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Re: Old reading about the isothermal lamp shape « Reply #5 on: March 25, 2021, 04:02:49 PM » Author: magslight
@Andy: Can you show your lamp here?  ;D
The dashed line fits with the temperature. The drawing confuses a bit but it makes sense. Next to the arc tube is the hottest part.
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Re: Old reading about the isothermal lamp shape « Reply #6 on: March 26, 2021, 10:11:06 AM » Author: Andy
@Andy: Can you show your lamp here?  ;D
The dashed line fits with the temperature. The drawing confuses a bit but it makes sense. Next to the arc tube is the hottest part.

I have some photos of the MAF/V lamp in my gallery that I took a few years back.
Yes next to the arc tube is the hottest part but to me the illustration shows the temperature scale contradicting this.

 
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Old reading about the isothermal lamp shape « Reply #7 on: July 30, 2021, 05:31:06 AM » Author: Olav
I found something about this type of lamp in a PHILIPS catalog from the late 1950s.
It was unknown to me that PHILIPS had also produced this type.


Source: PHILIPS Lamp Catalogue, exact year unknown.

Greetings from Hamburg

Olav
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sox35
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Re: Old reading about the isothermal lamp shape « Reply #8 on: July 30, 2021, 07:53:48 AM » Author: sox35
@Olav - this is a wonderful lamp shape, I would love to find one of these some day  :bulbman:
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