Reading: mv medium pressure lamp with isothermal outer bulb shape

[Olav]

About the history:

I am showing some text from a specialist book and a PHILIPS-catalog on an MV medium-pressure lamp with an isothermal bulb shape and phosphor.

Andy Oakley owns such a lamp. My wish is to see this photo here, too.



Source: PHILIPS-catalogue Australia, 50s


Source: ELECTRIC DISCHARGE LAMPS, by H. COTTON, LONDON 1946, CHAPMAN & HALL LTD.


Source: ELECTRIC DISCHARGE LAMPS, by H. COTTON, LONDON 1946, CHAPMAN & HALL LTD.


Source: ELECTRIC DISCHARGE LAMPS, by H. COTTON, LONDON 1946, CHAPMAN & HALL LTD.


Source: ELECTRIC DISCHARGE LAMPS, by H. COTTON, LONDON 1946, CHAPMAN & HALL LTD.


Source: ELECTRIC DISCHARGE LAMPS, by H. COTTON, LONDON 1946, CHAPMAN & HALL LTD.


I suspect this type was one of the first mv lamps with a phosphor.
To the admins: if this pictures are too big, please let me know.

Regards

Olav

[Andy]

Thanks for uploading this Olav.

The pictures are not too big, they are nice and clear!

I have the GEC 400W MAF/V lamp but have never seen a photo of this Philips version.
I'd like to think that a some examples might survive somewhere and be found one day.

[Olav]

Hello Andy,

thanks for your answer. I can well imagine that the lamps with the inscription "PHILIPS" were also manufactured by GEC.
Is that a theory too distant from me? You can measure your lamp. So we could compare something with the data in the PHILIPS catalog.

Regards

Olav

[Andy]

I have a feeling that you are correct about this.
It could be an early case of 'rebranding'.
The lamp is packed away very carefully and will take me some time to get to it but when I do, I will measure it and let you know.
The picture of that lamp looks exactly the same in every way as the GEC version.

[Alex]

I find that honestly quite interesting because at least from my experience rebranding at that time was less popular than after the second world war.
I had a look at the catalogues ad James's website. This lamp only appeared in the 1952 catalogue for the UK. In the 1953 catalogue for the UK it is missing. As i doubt that this lamp would have been made exclusively for Australia a think that this lamp was taken out the portfolio for that time.

Another thing: In the Philips catalogue of 1952 there is noted something in my opinion may be a strong indicator. All these lamps are made in Great Britain. While i think it is plausible for most MA and MB lamp to be made by Philips in the UK, i find somehow hard to believe that this rather unique lamp which needed a specialised envelope plus a novel phosphor, which was 40% more expensive and had 1600lm less then the standard MA/V lamp would be manufactured in the UK and not at Philips main HID Plant in the Netherlands, or at both plants. I somehow feel that is unlikely. Also This lamp has a typical after war/during ware base. If looked carefully on the picture on olav´s first scan, it can be seen that the insulator on the lamp is ceramic rather then the more popular vitrie. I noticed that many Lamps made in the UK during or shortly after the second world have used ceramic rather the n nitrite as an insulator making it not unique to GEC lamps.

The another thing is: The size of this lamp in the catalogue GEC lamp and the BTH lamp perfectly however the BTH lamp has a different shape (no dome but a dimple) and a shifted light centre compared the the GEC lamp. It would be interesting to know the light centre of this Philips lamp but i could not fin any data regarding that.

Notably, the Philips lamp is also 12% more expensive (£4 1s 6d VS £3 12s 6d (With 20s=£1 and 12d=1s) with the BTH and GEC lamp costing the same. (Maybe there was a constance mark up to make sure customers come directly to GEC...)

In my opinion it is possible maybe even likely that this is a GEC rebrand. However, i think to finally clarify that it would be necessary to compare modern state of the art pictures of both lamps which will be very difficult. These lamps as incredible rare and the Philips lamp being more expensive will be much rarer the the GEC and BTH lamps.

[dor123]

I thought that the MAF/V have an additional cadmium to correct the greenish colour back to white?
I've never know Philips also made a MAF/V lamp.

[Alex]

Your partly right dor123. Cadmium on it's own is just plain however very toxic metal. So Cadmium own its own won't to much of colour correction, maybe act as filter if applied thin enough like in Philips decorative gold and silver coated lamps.
In order to shift the colour temperature, which is done here, so called phosphors are used in order to extend the wavelength of light emitted. The compounds used do not have to contain phosphorus. With these very early lamps the active components are Zink Sulfide and cadmium sulphide which both are doped with extra metals like Copper (GEC lamp) and Copper and Silver (BTH Lamp).
Zink Sulfide is rather colourless, and glows what i would best describe lime green. It has its peak at about 510nm id say. It is the same fluorescent material used in old magic eye radio tubes.
Cadmium Sulfide on the other hand is brightly yellow. It was used as colour filter in old and yellow fluorescent tubes, and likely also to colour yellow incandescent lamps. It also the compound that gives these lamps their golden colour. It is responsible for the red (approx. 650nm) peak in this lamps spectrum.

Another thing i think i forgot to mention: It is remarkable that the advertised lamp life is with 1500hrs much lower then the 6000hrs for standard Philips MA/V lamp. Also its much less then the 5000hours adverted for the BTH lamps. Sadly for the GEC lamp, which would be of main interested here, its lifespan expectancy is unknown.

EDIT

RED marked sections are likely not correct. The two described wavelengths seem to originate from the additional Cd in the lamps arctube. See next post by myself

[dor123]

GEC and Mazda had cadmium and even zinc in the arctube, in additional to the Zinc Cadmium Sulfide phosphor
1. http://www.lamptech.co.uk/Spec%20Sheets ... MAF400.htm
2. http://www.lamptech.co.uk/Spec%20Sheets ... MAF400.htm

[Alex]

Okay, now i understand what you mean. I misunderstood your previous post. Yes both lamp contain additional Cadmium metal in the arctube. Not sure about the Zinc tho.


The Cadmium gives the lamp another blue line at around 485nm and also the green line at around 510nm which i attributed to the Zinc Sulfide. I have corrected it in my previous post. It seems by comparing both the spectra of an MA lamp, a Cd lamp and these MAF/V lamps that the phosphor only slightly shifts the spectrum to red. But the effect seem to be very minimal. Another possibility is that one phosphors shifts the colour towards red while the other adds more blue, as the yellow colour of the CdS filters a lot of blue...