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# This some kind lightbulb or...

Jan 18, 2016
138
Is this thing a light bulb or some kinda supernatural talisman? If it's a bulb how many volts would it take and why does it has 3 leads on it?? If it's a supernatural talisman, how many volts would it take? Pic incoming!

Jan 18, 2016
138

#### Gryd3

Jun 25, 2014
4,098
To be honest, I don't know, but it almost looks like a neon...
Tubes, and flash bulbs can use more than 2 leads. Often for biasing to allow the two main leads to discharge.
Where did you find this?

#### Harald Kapp

##### Moderator
Moderator
Nov 17, 2011
13,793
This is a neon lamp. Probably meant to be operated directly from mains (115V in the US). Why this model has three electrodes I can't answer.

Jan 18, 2016
138
Oh yea I shoulda told you that. I got this out of the guts of a fire/security alarm. The kind for a business that has all the circuitry inside a locked metal box. The... talisbulb was found inside that box where it could only be seen during maintenance or something. Gosh, never expected to read "I don't know" here. Well, a buddy of mine once said the statement "I do not know" is the beginning of all knowledge.

Jan 18, 2016
138
Also, it cares not for 3, 5 or 12 volts. These values do not excite it in the slightest. But.... man 120v?! That tiny lil bulb?

Jan 18, 2016
138
You guys gotta figure it out, pull out your textbooks, I promised the victims of that fire that I would do something real cool with that bulb!

#### davenn

Moderator
Sep 5, 2009
14,301
As Harald said, it IS a dual Neon globe
they require around 90V AC to strike and anything over around 100V they should be using a resistor in series to limit the voltage

Dave

Jan 18, 2016
138
Ah jeeze I dont have 90V converter... the internet says it can take AC or DC, couldnt I just use 120V and keep it at 400 μA (as wiki suggests) with resistance, R=120V/0.0004A ? Or do I need a punch in the face for suggesting it...

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#### davenn

Moderator
Sep 5, 2009
14,301
120V with resistor is OK

Jan 18, 2016
138
Rock on. Did I do that arithmetic right? So a 300kΩ resistor? Or better yet, three 100kΩ resistors in series?

#### hevans1944

##### Hop - AC8NS
Jun 21, 2012
4,891
It is a cold-cathode neon trigger (thyratron) lamp. I used one of these in the mid 1960s to build a full break-in keyer for my home-brew 80m Novice radio transmitter. The device was used to short my Heathkit SB-301 receiver antenna input each time the transmitter was keyed on, thus protecting the receiver from my mighty 70 watt RF output. Worked great! Unfortunately, at that time hardly any amateur radio operators were equipped for (or even knew about) full break-in keying or QSK as it is called. I liked it because I could receive transmissions from other hams in between Morse code character transmissions by me. During the time I was active as a Novice I don't recall "working" any ham who had QSK or knew about it. Today, everyone can use it. Most newer ham "rigs" are equipped for QSK operation even if the appliance operator isn't aware of it. See attached datasheet for an example type of this device.

#### Attachments

• CV2486.pdf
119.3 KB · Views: 68

#### Gryd3

Jun 25, 2014
4,098
It is a cold-cathode neon trigger (thyratron) lamp. I used one of these in the mid 1960s to build a full break-in keyer for my home-brew 80m Novice radio transmitter. The device was used to short my Heathkit SB-301 receiver antenna input each time the transmitter was keyed on, thus protecting the receiver from my mighty 70 watt RF output. Worked great! Unfortunately, at that time hardly any amateur radio operators were equipped for (or even knew about) full break-in keying or QSK as it is called. I liked it because I could receive transmissions from other hams in between Morse code character transmissions by me. During the time I was active as a Novice I don't recall "working" any ham who had QSK or knew about it. Today, everyone can use it. Most newer ham "rigs" are equipped for QSK operation even if the appliance operator isn't aware of it. See attached datasheet for an example type of this device.
Very nice Hevans! Thank you for sharing.

#### hevans1944

##### Hop - AC8NS
Jun 21, 2012
4,891
Very nice Hevans! Thank you for sharing.
I wish I could find some more of these to play with. The original that I used was a NE-xx where xx is now forgotten. Google has been of no help so far, except to eventually turn up the British CV2486 datasheet, no doubt obsolete and unobtainable now.

#### brevor

Apr 9, 2013
87
Bulbs like yours are frequently wired across the telephone line connectors on alarm systems to shunt high voltage transients to ground to protect the circuitry.

#### hevans1944

##### Hop - AC8NS
Jun 21, 2012
4,891
Bulbs like yours are frequently wired across the telephone line connectors on alarm systems to shunt high voltage transients to ground to protect the circuitry.
Great! Can you provide a part number or a source of supply? Here is a datasheet for a Russian version.
And here is an explanation for a touch-sensor circuit that uses the NE-77 (scroll down to TOUCH SWITCH):

Uses NE-77 neon lamp, which is similar to NE-2 but has third electrode for triggering. When person touches metal sensor plate of switch, AC voltage picked up by body is applied to trigger electrode of neon, making it fire and energize 5000-ohm relay K1 (Potter & Brumfield RS5D or equivalent). Relay remains energized until S2 is opened to reset circuit. Adjust R1 so voltage applied to center electrode of V1 is just below trigger point.-J. P. Shields, How to Build Proximity Detectors & Metal Locators, Howard W.Sams, Indianapolis, IN, 2nd Ed., 1972, p 52-55.

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#### Gryd3

Jun 25, 2014
4,098
Great! Can you provide a part number or a source of supply? Here is a datasheet for a Russian version.
Like a kid in a candy store
I tried some google Fu to see what I could find, but I'm not familiar with them so I thought I'd simply end up linking a bunch of useless random parts.

#### hevans1944

##### Hop - AC8NS
Jun 21, 2012
4,891
Well, at least I was able to eventually find the NE-77 part number. Probably unobtainable part now, but maybe those clever Chinese will start manufacturing them again. No exactly rocket science.

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