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Old 10th Aug 2022, 11:47 am   #1
Syrinx1
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Default Light bulb Identification.

Hello,

Just wondering if anyone is able to Identify this old light bulb \i found among my stuff.

The only marking I can see are the numbers 403 on the base.


Thanks,

Jonathan.
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Old 10th Aug 2022, 11:54 am   #2
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Default Re: Light bulb Identification.

At first sight I thought it was an old transmitter dummy load but I would say it is a photo cell? John.
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Old 10th Aug 2022, 12:08 pm   #3
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Default Re: Light bulb Identification.

Have you tested it with a series resistor to see if it is a Neon?

What size is it?
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Old 10th Aug 2022, 12:09 pm   #4
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Default Re: Light bulb Identification.

Quote:
Originally Posted by Heatercathodeshort View Post
At first sight I thought it was an old transmitter dummy load but I would say it is a photo cell? John.
I agree, it's a photocell.

Ian E

Addendum: See https://www.electricstuff.co.uk/Photocell.html "2nd row, 2nd tube from the left.

Last edited by Ian E G7OLT; 10th Aug 2022 at 12:31 pm.
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Old 10th Aug 2022, 12:17 pm   #5
Syrinx1
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Default Re: Light bulb Identification.

Hi, thanks.

I haven't performed any testing on it yet. Looking at the construction of photo cells it does look structurally similar.
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Old 10th Aug 2022, 12:19 pm   #6
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Default Re: Light bulb Identification.

I also agree that it is a photo cell.
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Old 10th Aug 2022, 12:22 pm   #7
Syrinx1
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Default Re: Light bulb Identification.

It's about the same size as a domestic incandescent light bulb, and has two wire connections that feed into the side of the base.
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Old 10th Aug 2022, 3:20 pm   #8
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Default Re: Light bulb Identification.

Does it's resistance change depending on how much light falls on it? If so...it works.

Dave
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Old 10th Aug 2022, 4:35 pm   #9
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Default Re: Light bulb Identification.

It may need an 'exciter' voltage to kick it off. Not sure. John.
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Old 10th Aug 2022, 5:01 pm   #10
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Default Re: Light bulb Identification.

I'll do some experimentation later tonight (no innuendo intended).
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Old 10th Aug 2022, 5:24 pm   #11
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Default Re: Light bulb Identification.

https://www.pinterest.com/pin/7a-we-...9843843643850/
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Old 10th Aug 2022, 5:45 pm   #12
Syrinx1
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Default Re: Light bulb Identification.

I managed to sneak off and test this, and indeed resistance does increase in the dark so this is definitely a phototube. I see these were used for "Optical sound" in film projectors among other things.

Would these also have been used in laboratory equipment - spectrometers etc?

I also had some photomultipliers in the same storage box.
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Old 10th Aug 2022, 5:53 pm   #13
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Default Re: Light bulb Identification.

Quote:
Originally Posted by Ian E G7OLT View Post
Quote:
Originally Posted by Heatercathodeshort View Post
At first sight I thought it was an old transmitter dummy load but I would say it is a photo cell? John.
I agree, it's a photocell.

Ian E

Addendum: See https://www.electricstuff.co.uk/Photocell.html "2nd row, 2nd tube from the left.
Yes looks identical to the one indicated in your link Ian.
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Old 10th Aug 2022, 5:55 pm   #14
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Default Re: Light bulb Identification.

Quote:
Originally Posted by barrymagrec View Post
And identical to this one too in appearance.

Thanks.
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Old 11th Aug 2022, 2:39 pm   #15
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Default Re: Light bulb Identification.

Quote:
Originally Posted by Syrinx1 View Post

I also had some photomultipliers in the same storage box.
What PM tubes do you have?
I've got this 931-A

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