Neon Lamps
Neon lamps are used for at least three different things in Tek instruments:
- Indicator lamps, e.g., for power, beam position, uncalibrated status, or a decimal point
- Voltage clamp, similar to how a zener diode is used
- In relaxation oscillators, e.g. in 7000-series power supplies
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
| 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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