Component Identification

[Bob R]

I need help identifying a component from a 110 VAC neon bulb circuit in a vintage GE alarm clock. The component is a black cylinder approximately 1/2" long and 1/8" in diameter. It has two color bands, one green and one yellow. This component and the neon bulb were wired in series across 110 VAC with the green band end soldered to one of the bulb leads. I've measured 122 VAC across the circuit, 108 VAC across the bulb, and 32 VAC plus 14.4 VDC across the mystery component. The positive lead of my VOM contacted the yellow band lead of the component.

 

[kellys_eye]

Very likely to be a resistor as these are used in series with neon indicators. You are SURE it's a neon indicator though?

Due to the extremely low current consumption of the neon it is likely that your meter has made a significant effect on your voltage readings hence them being out of kilter with what you should read - i.e. the sum of the individual series voltage measurements should total the supply across the whole circuit.

Many neon resistors are in the 100's of k-ohms and even megohms hence currents of 10's of microamps and LESS are flowing - far more being drawn by your meter, hence the readings.

If the neon is lit there isn't really a problem, is there?

 

[Bob R]

Thank you very much for your reply. I need to replace the component because it measures open now, no resistance. Initially, before the component failed completely, the light was flickering. I made my voltage measurements with my Velleman VOM, not a very sophisticated instrument, so you are probably right about the inconsistencies in the measurements. At this point I believe I will look for a new bulb/resistor combination suitable for a 110 applied voltage.

 

[davenn]

I need to replace the component because it measures open now,

Neon bulbs measure OPEN circuit when they are tested !!

 

[Externet]

A flickering neon bulb tells it is tired. Try replacing the bulb instead of the series component.

On the subject, a small value capacitor in series would be also a current limiter for a neon, but I have never seen such configuration used. Have you ?

 

[73's de Edd]

" a vintage GE alarm clock " . . .doesn't cut it . . . need its G.E.model number.
That equates with as much interpretable info as . . . .a vintage FORD car . . . .
Ditto on the need to just completely replace the lamp if . . . . .the light was flickering . . .
during the last gasp of it's lifespan.

 

[Bob R]

To clarify, it is the component that measures open. I believe the component has failed.

 

[kellys_eye]

Replace it with a 470k 1/4watt resistor (yellow, violet, yellow) and I think you'll find the neon works perfectly ok.

 

[Bob R]

Thanks to all who responded. I'll post the solution when I get the parts and complete the repair.