Does your electrostatic do this cool thing?

[jpdylon]

I've been testing and adjusting my old motorola 7vt5 since the re-cap and It's looking much better with a functional focus control

After about 20 minutes of watching i shut it off and headed back to my bedroom. When leaving I turned off the lights and noticed a flashing at my workbench. Looking at the tv in the dark I saw some flickering on the tube face. About every 10-20 seconds, what looked like watching a lightening storm through clouds briefly appeared on the screen. It did this for what must have been 5 minutes before the tube face was completely dark again.

I was just facinated. I've never seen such a thing before. Keep in mind the set was unplugged and away from any power source. I wish I coulda cought it on video (might have been too dark) I thought it was cool.

Anybody else who has an electrostatic set seen this before?

[blue_lateral]

I have seen old b/w sets that weren't electrostatic do this. I don't think I've ever seen one carry on for 5 minutes.

John

[kx250rider]

Call the Ghostbusters!

Actually, I would say that it's stray electrons in the tube striking the still-charged face. That TV probably has no high voltage bleeder, and has no aquadag coating on the tube. So the high voltage just sits in there for awhile with no path to ground except through striking the phosphor. Kind of a miniaturized Ball-Lightning phenomenon.

Charles

[compucat]

My Motorola 9VT1 is an 8" electrostatic set and it does this all the time in the dark. It is normal for this type of set. It is rather strange because you can watch it slowly build up to a bright flash. I'm glad my wife has never noticed it because she would be convinced there's a ghost in it.

[andy]

...

[bgadow]

I haven't run my single electrostatic set in some time so I can't remember what kind of show it put on. The longest I've seen is from a 12" round Philco which flashes for many minutes. The prettiest light show is from a 68 Zenith color console which puts out a psychedelic kaleidoscope that lasts a few seconds.

[jpdylon]

Ah yes, the 68 zenith I sold Adam did the same thing. Soon as you turn it off, it gave out this neat circle of colors for a few seconds.

I always liked some of the sets that would simply have the picture shrink until it turned into a little bright dot when you turned them off. i wonder how many small kids were facinated by this after watchin the tube, and if it was ever harmful to the CRT to have that bright dot....

[Sandy G]

Hell, Jordan, that was half the fun of watching an old set...Watching the little white dot get smaller, & finally go away...I always wondered if the program was still "playing" in the little dot...Kinda on the same line of thinking if the light stays on in the fridge after you close the door...I was a WEIRD kid, worrying about stuff like that...And I ain't got any better as time went on...<grin>-Sandy G.

[Celt]

Originally Posted by Sandy G

Hell, Jordan, that was half the fun of watching an old set...Watching the little white dot get smaller, & finally go away...I always wondered if the program was still "playing" in the little dot...Kinda on the same line of thinking if the light stays on in the fridge after you close the door...I was a WEIRD kid, worrying about stuff like that...And I ain't got any better as time went on...<grin>-Sandy G.

Sandy, as a kid, I shared the same fascination. (Loved that rainbow effect too!)

I'm not technical enough to know electrostatic from non, but my 10" Admiral bakelite set with original CRT does this same thing. The flickers seem to be in random "corners" of the screen but mostly the bottom right, they vary in brightness and there can be a few to several seconds between them. The set has to have run for a while before it will do this after shutting down. If I turn it off after only 5 or 10 minutes I will get a white dot but no flickering.

Growing up the sets I watched as a kid did more of the shriking to a dot routine and I don't remember any flickering like my Admiral makes.

With my rudimentary knowledge I was figuring it was a situation of left-over electrons like Charles describes above. Glad to read here that this doesn't appear to be a sign of any pending trouble.

[Adam]

My Motorola does exactly the same thing with the flashing.
I've also noticed, although I've only tried it with electromagnetic B&Ws, is if you turn the brightness down for a while before turning it off, the dot is brighter and lasts longer. I've always liked those sets where the picture settles down into a horiz line first before collapsing into a single dot.

[Eric H]

Adam, you should try to keep the dot to a minimum, it could eventually burn a spot into the phosphor.

Someone mentioned once how to stop it, possibly a bleeder resistor on the HV or something, anyone know?

[nasadowsk]

My brother's mid 80's Zenith has such an agressive natural glow to the CRT, you can cearly see it in the dark.

Even worse is my tek 545A scope. The screen *glows*. Hasn't been on for months but glows anyway.

Had an RCA HiLite 21FJP22 that did the same thing, but really dim. Just enough to notice it. Spooky to wake up at 2am and see that roundie outline just abut glowing...

[old_tv_nut]

In sets that show the dot or line at shut down, it's OK, or the manufacturer would have had to do something to prevent eating a lot of burned picture tubes. I saw this happen at Motorola on one early model of ttansistor B&W chassis. I can't remember the exact cause, but if you turned it off with the on-off switch, the tube was discharged enough before the raster shrank.. HOWEVER, the first factory run had the last person on the line pulling the line cord, and the video drive would go to cutoff immediately, with a spot appearing and burning the tube a long time after. Well, they were pulling the plug, putting the set in the box, and the burn would happen when the set was out of sight. When the box was opened, there was a burned tube! They had to put in a zener that pulled down the video drive as soon as the B+ died, causing a bright flash as the raster was collapsing but not yet down to a dot.

[old_tv_nut]

Another thing on those flashes - I vaguely recall seeing something similar around the edges of magnetically deflected tubes, maybe on turn on when the HV comes up before the filaments??? I wonder if there is any static buildup on the bezel - I'd be tempted to try running my hands around the face after turning it off to see if I could cause the flashing.