DIYbanter - View Single Post - NE-51 Neon Bulbs

bud--

On 11/24/2015 3:32 PM, wrote:
On Friday, November 20, 2015 at 3:55:22 PM UTC-5, Madness wrote:
Just acquired a bunch of these lamps. They're in the same mini-bayonet
style as lamps like the #44/47. But would anyone know if these lamps can
be connected directly to 120 volts? Or do they need a resistor, @ if so,
what value?

Mpfffff....

This lamp was used by Zenith and more than a few other manufacturers in the 1950s/1960s as an indicator lamp (on/off) at about the time that radio manufacturers started to become concerned about user-servicing and hot-chassis radios - something that never really bothered them in the past. The worked on the theory that a neon lamp was far less likely to burn out than the old standby #44 or #47, so that loose fingers were less likely to get nipped. ASIDE: Audio devices held on to incandescent lamps (With specific reference to the 47) well into the 80s, before shifting - very slowly - to LEDs or Fluorescent lamps. But, they had transformers on board to isolate the chassis.

It is designed to operate at ~120V AC. It _CAN_ operate at ~120V DC, but only one post will light. It will trip (glow) at about 90V +/-.

Unless there is a voltage dropper in the circuit, it will fail quickly at 220 or 240 V - that is voltages outside of Japan and the Americas. As supplied, it has a 100K resistor in series with the lamp. For conversion to 220V, I have heard values of up to an *additional* 220K in series. Try there and work back if you wish to operate at 220V.

It will fail immediately without a series resistor.
As others have said, there is no resistor built into the lamp.

From a 1965 Allied Radio catalog, Chicago Miniature lamp:
NE-51 is clear glass tubular, single contact bayonet base.
Voltage across the lamp is 65V when operating at the rated 1/25 watt.

A higher voltage is necessary to ionize the neon (which is why a
relaxation oscillator works). The voltage is somewhat constant with
varying current. At 1/25 watt and 65 volts the current would be 0.6 mA
and the series resistor for 120V supply would be 91k (minimum).

There is also a NE-51H that runs at a blinding 1/7 watt (2 mA).

As about 2/3 of my hobby time is dedicated to vintage radios, I am quite familiar with, and keep a bunch of these lamps in my spares-box.

Peter Wieck
Melrose Park, PA