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Old 11th Jun 2021, 7:54 am   #1
Paul Mathew
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Default Selenium Rectifier Globe (Lamp) Query

The globe in the pic attached is in series with the mains HT AC side of the rectifier, and gradually starts to glow after switch on to give the valve heaters time to get up to temp.
Can someone enlighten me on the type of globe used?
The voltage drop across the globe reaches 2,7 - 2,9V.
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Old 11th Jun 2021, 8:31 am   #2
Mr 1936
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Default Re: Selenium Rectifier Globe Query

Hi

Difficult to be sure, but it looks like a miniature bayonet cap light bulb, the sort that would be used for old fashioned torches or radio dial illumination.

Assuming that it doesn't glow at full brightness, it could be rated at 6 volts 0.3 amps, but that's only a guess.

Looks like a retrofit.
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Old 11th Jun 2021, 8:59 am   #3
murphyv310
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Default Re: Selenium Rectifier Globe Query

Probably used as a fuse.
I'd say a 100ma bulb, if an HT short occurs or fault in the rectifier it would blow. Definitely a retro fit.
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Old 11th Jun 2021, 10:22 am   #4
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Default Re: Selenium Rectifier Globe Query

Are the bulb's (globe's) ratings not marked on its metal base?


They may be somewhat difficult to read- a bright light and magnifying glass are handy!
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Old 11th Jun 2021, 11:44 am   #5
Paul Mathew
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Default Re: Selenium Rectifier Globe Query

The globe has GE 57 and what appears to be CANADA printed on it. If it were a regular globe wouldn't it glow at its full brightness on switch on? It takes about 5 - 10 sec to warm up.
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Old 11th Jun 2021, 11:52 am   #6
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Default Re: Selenium Rectifier Globe Query

At switch on the valves take time to pass sufficient current to illuminate the bulb.

Lawrence.
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Old 11th Jun 2021, 11:53 am   #7
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Default Re: Selenium Rectifier Globe Query

Quote:
Originally Posted by Paul Mathew View Post
The globe has GE 57 and what appears to be CANADA printed on it. If it were a regular globe wouldn't it glow at its full brightness on switch on? It takes about 5 - 10 sec to warm up.
It is in series with the HT as Murphy310 has said its being used as a fuse bulb.
It will only start to light once the valves start to draw HT.

In the US they often numbered small lamps rather than putting their ratting on the lamp itself.

Haven't had time to check but I think a 57 is a 14V 3.3W MBC

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Old 11th Jun 2021, 12:48 pm   #8
Paul Mathew
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Default Re: Selenium Rectifier Globe Query

Great. Thanks for the feedback.
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Old 11th Jun 2021, 8:25 pm   #9
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Default Re: Selenium Rectifier Globe Query

OK finally remembered where to find the list of US lamp types.

Hopefully the link will work for non members

https://www.radiomuseum.org/forumdata/upload/lamp1.png

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