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Osram-GEC 400W MA/H Lamp for horizontal burning A rare and rather interesting one this, I'm not 100% sure how best to run it at the moment, as the leaflet with it says it needs a special choke tapping; I am reliably informed that the lamp should be run at 4.2A rather than the usual 3.25A, some thought is going to be needed here..! It is shown running here on a normal 3.25A ballast, as I hadn't fully read the leaflet (oops) but that was only for 10 minutes to take the photos. Keywords: Lamps

Osram-GEC 400W MA/H Lamp for horizontal burning


A rare and rather interesting one this, I'm not 100% sure how best to run it at the moment, as the leaflet with it says it needs a special choke tapping; I am reliably informed that the lamp should be run at 4.2A rather than the usual 3.25A, some thought is going to be needed here..! It is shown running here on a normal 3.25A ballast, as I hadn't fully read the leaflet (oops) but that was only for 10 minutes to take the photos.
DSC02617.JPG GEH100A4-T.jpg Iwasaki_EYE_50W_Clear.jpg Bumix_Jupiter_Lamp_2~0.jpg Osram-GEC_400W_MA-H.jpg
Lamp/Fixture Information
Manufacturer:The General Electric Company of England
Model Reference:MA/H
Lamp
Lamp Type:Medium pressure mercury lamp
Filament/Radiator Type:Aluminosilicate glass arc tube
Base:E40
Shape/Finish:Tubular, clear
Burning Position:Vertical cap up to horizontal
Electrical
Current:4.2A
Physical/Production
Factory Location:Shaw, Oldham
Fabrication Date:March 1960 (Date code RC)
File information
Filename:Osram-GEC_400W_MA-H.jpg
Album name:Ria / Mercury Lamps
Keywords:Lamps
Filesize:348 KiB
Date added:21 Jul 2024
Dimensions:2245 x 1587 pixels
Displayed:863 times
URL:https://trad-lighting.net/gallery/displayimage.php?pid=81
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Comment 1 to 16 of 16
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Sammi   [Sun 21 Jul 2024 at 23:09]
Looking forward to seeing this rare beast lit again.! Cool
Ria   [Sun 21 Jul 2024 at 23:27]
Indeed, someone said a 400W SON ballast run at a slightly lower mains voltage should work, so we'll maybe try that soon.
Sammi   [Sun 21 Jul 2024 at 23:29]
As the correct ballast is unobtanium, that's the best we can do.
Tuopeek   [Tue 23 Jul 2024 at 21:36]
Think I have the same lamp, although with more hours on it. The start resistor has a connection issue but the outer jackets incomplete vacuum means it starts fine. I hadn't realised the current differs and have run mine up on a standard 400w MB/U mercury ballast. It does look like you might be running that horizontal though Surprised but I'm sure you know you need a magnetic deflector for that.
Sammi   [Tue 23 Jul 2024 at 21:38]
We are running it horizontally, and it was designed for that without the deflector, hence the higher current.
Tuopeek   [Tue 23 Jul 2024 at 21:46]
Wow, thanks for the information Sammi, I need to find out more on this and check if mine is indeed the same.
Sammi   [Tue 23 Jul 2024 at 21:48]
The MA/H lamps are like hen's teeth, our other ones, which look the same, are the usual MA/V lamps, have a shufti at the etch.
Tuopeek   [Tue 23 Jul 2024 at 21:57]
Ah, that sounds rare right enough think it might be the MA/V I have.
Ria   [Tue 23 Jul 2024 at 22:03]
Yeah, the genuine MA/H version is rather a rare beast, apparently it has a hard glass arc tube so is more able to withstand horizontal burning, but from what I can gather, the genuine ballast for it has a different tapping, not sure Confused
Tuopeek   [Wed 24 Jul 2024 at 21:38]
I see what you mean, it looks more or less physically identical to the MA/V. Surprised Also see a mention to 'special choke tapping' for the MA/H but not 100% clear if that's on the 400w MA/V choke. Glad you have this in your collection I would have missed this otherwise
Sammi   [Wed 24 Jul 2024 at 21:39]
So are we.! Laughing
Ria   [Wed 24 Jul 2024 at 21:44]
@Tupoeek - I think there was a special ballast for it, but not sure. I'm guessing so, given the higher current requirement.
Max   [Fri 01 May 2026 at 17:37]
Somehow I missed this post. Really interesting lamp! Although I knew about the /H variant of this MA type, I had not realized that electrical characteristics where so much different! It looks like the mercury pressure is reduced in order to lower the heat transfer from the arc to the glass wall, a trick used also by GE in its 250 W A-H2.
Ria   [Sat 02 May 2026 at 00:21]
I haven't tried running it again since I took this picture, I'll try using the Variac to alter the lamp current and see what happens.
Max   [Sat 02 May 2026 at 05:36]
Those lamps operate in the unsaturated vapor regime, changing the current (over a reasonable range) won't change its discharge properties much. Have you measured its voltage? It should be lower than that of the /V variant.
Ria   [Sat 02 May 2026 at 11:51]
Not yet, but we'll get the lamp out soon and try a few things.

Comment 1 to 16 of 16
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