Neon Lamps

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

1. Indicator lamps, e.g., for power, beam position, or uncalibrated status
2. Voltage clamp, 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.

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

Types and data

• See Neon lamp specifications

Type	Tek part no.	Ignition voltage (V)	Maintaining voltage (V)	Design current (mA)	Notes
NE-2		76 (60−90)	58	0.3
NE-23		74 (60−90)	59	0.3	"mild radioactive additive for reduction of dark effect"

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See also

• Nixie tubes
• Voltage regulator tubes