Howto Use 120VAC rated Neon Indicator on 240VAC Circuit

[edtyler]

HI,

I need to replace a defective 240VAC Neon indicator on a power supply.

There is no 120VAC anywhere in the device, as it is powered from the 2 non-grounded conductors in a typical US residence. There is a ground, but it should never be used to carry current.

I have a supply of 120VAC rated Neon indicators that I'd like to use. These, presumably, have a series resistor to limit current once the lamp strikes.

It seems there may be two choices: 1)  add an additional series resistor, but I'm not quite sure how to calculate the value of this resistor. Perhaps the value would be (Desired voltage - rated voltage)/existing current when lit at 120V?

or 2) Hook up two of the 120V indicators in series. This may suffer from the problem that once the first bulb strikes, then the current limit resistors added together might prevent the second bulb from striking.. Also I have never seen this done - 2 neon bulbs in series..

I'm looking for ideas on which approach would be more reliable/practical. No, I don't want to buy a 240V rated neon indicator. Although I do have a supply of the 120V Neon indicators, I don;t really want to destroy too many of them doing testing.

Thanks in advance for any suggestions.

[NiHaoMike]

Try 100k, should be right in the ballpark when combined with the 33k or so already inside the indicator.

[bdunham7]

https://www.intl-lighttech.com/instrumentation-sensor-light-sources/neon-lamps