Modern variant of instant on?

[lnx64]

This is something that I have noticed with some later CRT TV's.

When turned on from cold, they seem to have a lot of brightness, then dark a little once warmed up, as if it leveled off.

On old TV's though, like the Samsung in my sig, they just startup dim until they brighten when fully warmed up.

Is this like a modern variant of instant on, without keeping the heaters on? Try and artificially increase brightness to make it look like the CRT is already ready to go even though it just turned on?

[radiotvnut]

My 2002 Sony 20" Wega does that and I believe this is due to the AKB (Auto Kine Bias) circuit doing it's thing as the tube warms up. I don't think there's been any "instant on" TV's made since the mid '70's.

[old_tv_nut]

Zenith's with AKB showed this kind of behavior, with each gun stabilizing at a slightly different moment as the three filter capacitors in the feedback circuit reached normal voltage, all three starting at zero but going to different levels depending on the gun characteristics.

[lnx64]

Hmm, how early did they use AKB?

I've even noticed my 80's IBM monochrome monitor starts out with a brighter than normal brightness/black level, until leveling off after it warms up.

[crtfool]

I have a 3" Quasar UP1315XQ that does exactly the same thing. When I turn it on, the brightness is very high and the black level is very washed out - it takes about 10 minutes for the picture to normalize with proper levels.

[radiotvnut]

I can't tell you when AKB circuits were first used; but, I know they were used in many mid '80's Emerson TV's.

[old_tv_nut]

If it snaps to a definite correct level in a few seconds, it's AKB - slow drifting is just slow drifting and obviously no AKB.

[Eric H]

Some models of Sony Trinitron would keep the CRT in cutoff until the guns all reached a certain level, then it would pop on all at once.
If the CRT got too weak to achieve a good emissions and balance it would stay in cutoff and you wind up with no picture at all, or one that flashes on and cuts back off.

[zenithfan1]

My 2004 30HS420 widescreen Trinitron does that Eric. CRT is like new, I guess I'll know what to look for when it isn't