OT-light bulb help

  • Thread starter Thread starter pheasant
  • Start date Start date
pheasant said:
Anyone care to take a 50 year step back in time to help me find a bulb for
an old GE alarm clock? Seems I replaced it about 15-20 years ago, but Radio
Shack doesn't have parts like they used to. Gave off a soft orange/red glow
almost like a mini neon tube. Hope there are a few old scroungers that
follow the group.

GE Model 7282K.
Here's the bulb.
http://i29.photobucket.com/albums/c298/pheasant16/alarmclockbulbssmall.jpg


Thanks!
Click to expand...

The only bulb I've ever used, is a NE-2 or equiv. It looks
similar to the one you've got.

http://www.jameco.com/webapp/wcs/st...storeId=10001&catalogId=10001&productId=27351

It's been years since I played with one. The series limiting
resistor is perhaps 220K ohms or so. That is about 500
microamps of current from the 120V AC line. (Not the 500
milliamps mentioned in the Jameco advert. Off by a factor
of a 1000.) Using a lower value limiting resistor (like
say 47K ohms) would make the bulb a lot brighter, but would
wear it out faster.

Bulbs have a "make" and a "break" voltage. They turn on at
one voltage (like 100 volts), and turn off when the voltage
drops (like less than 70 volts). They only light for part of
the 120VAC sine wave from the power company.

Unless the bulb has some specific function in a circuit,
and all you are after is a source of light, chances are
a NE-2 and a limiting resistor, is good enough. (Neon bulbs
can be used in relaxation oscillators, in which case using
an exact replacement may prevent the need to re-engineer
the circuit.)

There are some other ones, that have a couple metal
"rectangles" sealed inside the glass tube. Those give
a lot more light. But I've never seen a source of them
at retail where I live.

The place I bought my last NE-2's, gave me
their entire collection of them, because they were
tired of stocking them.

There are a bunch more choices on this page.

http://www.jameco.com/webapp/wcs/st...oreId=10001&catalogId=10001&categoryId=153050

Here is a datasheet for some of the types:

http://www.alliedelec.com/Images/Pr...ure-Lamp-Inc_Actives-and-Passives_7492100.pdf

Good luck,
Paul
 
Paul said:
The only bulb I've ever used, is a NE-2 or equiv. It looks
similar to the one you've got.
Click to expand...


Yep that sure looks like a NE2

If you want one and are in the US I'll send you one free
(though you may have to re-use the dropping resistor)

my gmail addy is philo565
 
Paul said:
The only bulb I've ever used, is a NE-2 or equiv. It looks
similar to the one you've got.
Click to expand...


Must be really dark around your house, that little bulb in your house
lighting fixtures.....
 
pheasant said:
Anyone care to take a 50 year step back in time to help me find a bulb for
an old GE alarm clock? Seems I replaced it about 15-20 years ago, but Radio
Shack doesn't have parts like they used to. Gave off a soft orange/red glow
almost like a mini neon tube. Hope there are a few old scroungers that
follow the group.

GE Model 7282K.
Here's the bulb.
http://i29.photobucket.com/albums/c298/pheasant16/alarmclockbulbssmall.jpg

Thanks!
Click to expand...

Just replace it with a bright LED lamp--all kinds/colors available. Just
tweak the voltage to match.
 
Just a standard neon lamp... surprised Radio Shack or Tandys don't
stock them. As the previous poster mentioned the series resistance is
about 220K, without the reisistor the lamp would probably work at
around 75V or so... these things only work on AC voltage and not DC.

Just two electrodes and a little inert gas that ionises under a ac
voltage.

As a thought why not use a LED these work at around 1.5V and consumes
about 10 mA or 0.01 Amp... you'll have a choice of colours red,
amber, green yellow blue or white but if using mains power the
resistance would have to be around 10K ohms due to the higher current
and would have to drop 113.5V , the resistor would need to have a 2
watt rating.

Some uV leds are available now one of these might prove interesting,
especially if the numbers are white on a black background the numbers
should really stand out.

From memory I repaired a Sony clock that used a mini uV flouresecent
tube years back, different LED's will require different resistor
values as the LEDs voltage and current may vary considerably.

Davy
 
pheasant said:
Anyone care to take a 50 year step back in time to help me find a bulb for
an old GE alarm clock?
Click to expand...

Thanks Guys!

philo generously offered to mail one and should have the clock up and
running again shortly.

I suppose next time it burns out, hopefully another 15+ years; it'll be
time to replace the clock, or like Davy says replace it with something
newer.

Mark
 
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