On Monday, February 1, 2016 at 10:09:10 AM UTC-5, N_Cook wrote:
On 01/02/2016 13:59, Chuck wrote:
There was an AOC tv in the mid 80s that had capacitance touch switches
on the front and the channel indicators were illuminated with NE2 neon
bulbs. An ic drove transistor switches that turned the bulbs on and
off. The sets would come in where the channel couldn't be changed.
The first one took me a few hours to repair. The soluton was to
change the NE2 bulb on the channel the set was stuck on. The faulty
bulbs still lit at the proper voltage. Anyone have an idea how the
bulb could cause this fault? At the time we were a high volume repair
service so I didn't have the time to ponder circuit anomalies. Thanks.
Chuck
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And another weird neon problem. My main bench power supply, I've never
had to go inside it , so this minor problem remains.
The mains-on neon never lights in sunlight or room light but comes on
and flashes if its night time and next to no low light in the room, if
the ps is left switched on. Its a pip type, only a pip protrudes through
the casing if that is relevant.
This is an easy one... your vision is not linear based on lighting conditions, but very relative. A flash or low glow in a neon bulb would be entirely invisible under normal-light conditions, but in low light, your heightened sensitivity would pick it up easily. Further, Neon lamps, after they trigger, are not like many LEDs which are on/off devices. Once they trigger, voltage may drop considerably and they will still remain lit. So, if there is a capacitor in the circuit to trigger it, then when it reaches that point and 'fires' the lamp will flicker. But the carrier voltage to keep it running is not there. So it is only a flicker.
Some SS-relay operated neon ballasts from the very early days of electronic ballasts behaved the same way if wired with the 'neutral' switched, or at 277V under some conditions. Firing voltage is achieved, but operating voltage is not present. They flash. And if, as in some Euro applications, the "neutral" is above ground, this can be a real issue. The ballast design changed pretty quickly for this reason.
Peter Wieck
Melrose Park, PA