On Monday, February 1, 2016 at 12:04:43 PM UTC-5, wrote:
There were also Sonys like that. I thought it was leakage in the neon that caused that failure.

Yes, NE2 lamps age, and their internal resistance changes as a result. So, if the circuit depends on 'sensing' the operation of the neon lamp, and the operating resistance changes sufficiently, the circuit will latch.

Small pen-type one-point voltage sensors discern between AC & DC by only one side or the other glowing under DC, both under AC. Back in the day where mains DC was common (up to 2007 in NYC), that was important to know at a glance.

http://cityroom.blogs.nytimes.com/20...s-edison/?_r=0

Peter Wieck
Melrose Park, PA