OT - CRT's

Jan Panteltje wrote: : On a sunny day (Mon, 27 May 2019 07:37:44 -0700) it happened John Larkin : wrote in : :

: >My uncle Sheldon, who started me in electronics, was a rascal. He had : >a TV repair service and had kids go out in trucks to make house calls. : >Some sets had the CRT and then a flat cover glass. If people smoked, : >particles would accumulate on the CRT face and make the picture dim. : >They'd take the set back to the shop, Windex it, and charge for a new : >picture tube.

: I had a TV repair shop for many years, : and you could increase brightness by wiping of the nicotine tar from the smokers with alcohol.

I remember reading in the UK's Television Magazine (sadly no longer published) in the days of System A / 405 lines that smoker customers would sometimes complain afterwards about the 'poorer' liney picture!

Tom.

Ps. The email address in the header is just a spam-trap.

--
Tom Crane, Dept. Physics, Royal Holloway, University of London, Egham Hill, 
Egham, Surrey, TW20 0EX, England.  
Email:  T dot Crane at rhul dot ac dot uk

Some fungi evolved, or already had, the capacity to live off gamma rays.

Nature is astounding.

If yoy weren't so universally (and clumsily) hostile and insulting, you might get a little respect.

--

John Larkin   Highland Technology, Inc   trk 

jlarkin att highlandtechnology dott com 
http://www.highlandtechnology.com

It was my understanding that it was possible to make electrostatic CRT deflection more linear than magnetic deflection but it couldn't be deflected as much. Linearity across the entire screen was rather important in an oscilloscope. The shorter tube (and therefore larger screen) more important in a TeeVee.

The Tek 7912 Transient Digitizer had a bandwidth >1GHz, though the fastest plugin was the 7A19, which limited it to 500MHz.

We had a few of the 7912s at IBM in the mid-late '70s. I used them, and the Tek Signal Processing System to look at secondary breakdown of some contactor drivers that were causing smoke in customer's offices (not good).

Scopes need plenty of bandwidth. You can't get that out of inductors.

1940s CRT TVs did use static deflection. A 7 or 9" set with a kilovolt to deflect it enough is limiting, you can't go higher V without creating added problems, and can't therefore go larger screen. Magnetics solves both issues.

NT

And, with the right predistortion, there are a few instances of magnetic-deflection oscilloscopes (like, a 22" screen for a lecture demonstration). It's not clear if those were good for anything higher frequency than audio.

whit3rd wrote in news: snipped-for-privacy@googlegroups.com:

Y'all know that special relativiety is in crt science too...

Essentially only an very large crt displays. The anode supply wave form is shaped to help take care of this.

I college, we had a bunch of the HP-140 series of demonstration scopes (HP donated *tons* of equipment to us). They weren't much good above audio, _maybe_ 1MHz. The HP-140 was only good to 20MHz, IIRC.