Neon Lamps

NE-2 neon lamp

Neon lamps are used for at least three different things in Tek instruments:

1. Indicator lamps, e.g., for power, beam position, uncalibrated status, or a decimal point
2. Voltage clamp or stabilizer, similar to how a zener diode is used
3. In relaxation oscillators, e.g. in 7000-series power supplies

Broken lead (left) on neon in 585 time base

Neon lamps fail more than most other components. A common failure mode is for the leads to break off, often close to the glass bulb, due to corrosion and vibration. Another failure mode is for the I-V characteristic to drift.

Neon lamps are used as a voltage clamp in the CRT circuit for setting the CRT grid voltage in many Tek instruments. A typical example is seen in the 561A:

If the neon lamps fail, the CRT grid voltage will be affected.

Another common use is for DC bias shifting, e.g. in 500-series timebase circuits, or the horizontal output of the 511. In such circuits, a 56 V Zener diode may be a possible replacement for the neon.

545 timebase: 511 H output:

When in doubt, replace the neon lamps. In a pinch, it may be possible to reattach broken leads after careful grinding of the glass.

Bruce Baur said:

I had to replace a neon that had a broken lead in a 511. It would oscillate. I had lots of neons and would put them on a curve tracer to check. All liked to oscillate. I would then take the neon and bang it on the table, trying to make the internal elements non parallel. I broke a few, but I finally got the internal elements non parallel and the low frequency oscillation stopped.

See also

• Neon lamp @ Wikipedia
• GE Glow Lamp Manual, 2nd Ed. 1965
• William G. Miller, Using and Understanding Miniature Neon Lamps (1969)
• Nixie tubes
• Voltage regulator tubes

Types and data

• See Neon lamp specifications

Type	Tek P/N	Voltage		Current	Notes
		Ignition	Operating	Nominal
NE-2	150-002, 150-0002-00	76 (60−90) V	58 V	0.3 mA	=~ modern type A1A
NE-2V	150-030, 150-0030-00	76 (60−90) V	58 (46-78) V	0.6 mA	short length, formed tip for end-on viewing; dark compensated; =~ modern type A2B
NE-23	150-027, 150-0027-00	74 (60−90) V	59 V	0.3 mA	dark compensated

Please add

Dark compensation

Neon lamps require a higher voltage to ignite if operated in total dark, this is known as Dark effect. This was compensated in some types by a "mild radioactive additive" to help with ionization, typically a small amount of Krypton-85 (beta emitter, 10.8 years half life) added to the gas filling.

After 50 years, radiation from this source will have reduced to ~3% of the intensity at new. Modern NE-2 variants will likely not contain such an additive in the first place.