How Come Early CRTs contained more Ions?

[zenith2134]

Wow, great replies. Thanks. So it is due to the gas inside the crt...I had a gut feeling it might be related to that, being that vacuum pumps probably got better as time went by...My oldest b/w sets have the ion traps in the neck but I never questioned why they did. No wonder why they can make or break the picture. On my Admiral, even the slightest adjustment hurts the contrast ratio.