View Single Post
  #10   Report Post  
Posted to sci.electronics.repair
Arfa Daily Arfa Daily is offline
external usenet poster
 
Posts: 6,772
Default Dumb TV question


"oldfogie" wrote in message
...
Yes, I'm sure, was a small glass neon bulb soldered to chassis.
I looked through a good many old Sams folders, back into the '70s & '80s
but never found a neon bulb in one. Problem is, just because it was near
the fly doesn't have to mean it was in the fly circuit. So it must have
been in some other circuit. I think it was for spike protection, for
whatever circuit it was in.
I'm ready to just forget it, not important.
Thanks to all for replies!




If it was a true neon bulb, then it wouldn't actually need to be connected
into any circuitry in order to light up as an indicator of flyback activity.
Most gas filled tubes will light in mid air if they are in close enough
proximity to a flyback tranny. Back when I was an apprentice, like 35 years
ago, the guy that I worked under in a TV workshop, used to keep a short thin
flourescent tube on his bench. He used this to test for horizontal output
stage activity, simply by waving it around the FB tranny. As I recall, he
used to reckon that he could tell a lot about how that stage was working,
when he had a lack of picture fault, just by the 'way' in which his little
tube lit up.

Most of the similar 'bulbs' that I've seen on CRT base connector boards,
have been gas-filled spark gaps. I seem to recall that they used to put
argon in them, and when they went off as a result of an inter-electrode
short in the tube, they lit up white, rather than the orange glow of a neon.

Arfa