[sdiy] Amps and neons - here's a good one!

[rburnett at richieburnett.co.uk]

As the neon bulb ages it's striking voltage increases.  Eventually the 
340V peaks of the mains supply (or 156V if you live in US) will not be 
sufficient to strike a glow discharge in the gas.  However, if vibration 
even momentarily reduces the gap between the electrodes then a discharge 
will be initiated at a lower voltage.  Once the plasma has struck it 
will remain lit for the rest of the mains cycle until the current goes 
through zero extinguishing the arc.  Old neon bulbs frequently flicker 
in an unstable manner when there is barely sufficient voltage available 
to reliably strike the glow discharge in the gas.

-Richie,

On 2013-02-11 18:05, Gordon JC Pearce wrote:
> I have an old HH VS120 combo, yes, the ones with the green glowy
> electroluminescent control panel (mine's worn out, sadly).
>
> The mains on/off switch is one of those rocker switches with a neon
> in it.  Now when the amp is on, the neon no longer lights - but it
> will come on in time with peaks in the music!
>
> Why is it doing this?  I notice that it does it more with bassy
> sounds - could it be that vibrations are being coupled into the lamp,
> making the electrodes wibble about, and lowering the striking 
> voltage?
> Seems unlikely...