OT - CRT's

[John Larkin]

On Tue, 28 May 2019 09:25:20 +0000 (UTC),
DecadentLinuxUserNumeroUno@decadence.org wrote:

Jan Panteltje <pNaOnStPeAlMtje@yahoo.com> wrote in news:qchd7d$gr0$1
@dont-email.me:

What bothers me is the fear mongering by clueless greenies.
There was a nice video of wildlife after Chernobyl on youtube
how it thrived, wolves, birds in the no go area,
and guess what, it is removed.

I saw it... years ago. But the video I saw DID show where
certain species were affected, and a couple new ones may have
morphed out of those.

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

https://en.wikipedia.org/wiki/Radiotrophic_fungus

Nature is astounding.

It DID have an effect. It is not about fear mongering, it is
about basic safety and truth. I doubt the video was removed. More
likely it was cancelled because the poster did not have the right to
post non-public material and the actual copyright owners got it
pulled. Why don't you try to find the video from its actual source?
Or noticing who made the video was not all that high on your brain
list of things to do...

Go build your house right over the failure location. Not out in
the zone... Right over ground zero.

You make some pretty dumb statements sometimes.

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

 

Jan Panteltje <pNaOnStPeAlMtje@yahoo.com> wrote:
: On a sunny day (Mon, 27 May 2019 07:37:44 -0700) it happened John Larkin
: <jjlarkin@highlandtechnology.com> wrote in
: <fatneel5b09lhggfbnith1j0016ermks2e@4ax.com>:

: >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

 

On Fri, 24 May 2019 20:12:45 -0700 (PDT), whit3rd <whit3rd@gmail.com>
wrote:

On Friday, May 24, 2019 at 4:51:24 AM UTC-7, DecadentLinux...@decadence.org wrote:

It was my understanding that CRTs ALL have magnetic field beam
deflection... in both vectors.

No, that's only for short ones with big screens. An oscilloscope that uses
a long tube, small screen, is of the electric field deflection type.

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.

 

On Sat, 25 May 2019 01:23:20 +0200, Gerhard Hoffmann <dk4xp@arcor.de>
wrote:

Am 24.05.19 um 23:55 schrieb John Larkin:
On Fri, 24 May 2019 13:14:58 -0700 (PDT),


And a companding 8-bit grey-code CRT ADC, used in the first PCM
telephone systems.

There were gas-filled CRTs where you could see the electron beam.


And a transient recorder by Tek based on a tube, 200 MHz IIRC.
Where usually is the phosphor, there were capacitors that
collected electrons from the beam and they could be read out.

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

They demo-ed us that thing, but we ended up with the newest
20 MSPS 8 bit flash ADC from TRW. A chip the size of a fingernail.

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).

 

On Friday, 31 May 2019 01:36:12 UTC+1, k...@notreal.com wrote:

On Fri, 24 May 2019 20:12:45 -0700 (PDT), whit3rd <whit3rd@gmail.com
wrote:
On Friday, May 24, 2019 at 4:51:24 AM UTC-7, DecadentLinux...@decadence.org wrote:

It was my understanding that CRTs ALL have magnetic field beam
deflection... in both vectors.

No, that's only for short ones with big screens. An oscilloscope that uses
a long tube, small screen, is of the electric field deflection type.

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.

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

 

[whit3rd]

On Thursday, May 30, 2019 at 5:36:12 PM UTC-7, k...@notreal.com wrote:

On Fri, 24 May 2019 20:12:45 -0700 (PDT), whit3rd <whit3rd@gmail.com
wrote:

On Friday, May 24, 2019 at 4:51:24 AM UTC-7, DecadentLinux...@decadence.org wrote:

It was my understanding that CRTs ALL have magnetic field beam

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.

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 <whit3rd@gmail.com> wrote in
news:98bbb772-327e-4915-afa7-893f0aae9784@googlegroups.com:

On Thursday, May 30, 2019 at 5:36:12 PM UTC-7, k...@notreal.com
wrote:
On Fri, 24 May 2019 20:12:45 -0700 (PDT), whit3rd
whit3rd@gmail.com> wrote:

On Friday, May 24, 2019 at 4:51:24 AM UTC-7,
DecadentLinux...@decadence.org wrote:

It was my understanding that CRTs ALL have magnetic field
beam

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.

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.

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

https://preview.tinyurl.com/y5ch3cm2

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

https://preview.tinyurl.com/y35nebe3

 

On Sat, 1 Jun 2019 01:35:07 -0700 (PDT), whit3rd <whit3rd@gmail.com>
wrote:

On Thursday, May 30, 2019 at 5:36:12 PM UTC-7, k...@notreal.com wrote:
On Fri, 24 May 2019 20:12:45 -0700 (PDT), whit3rd <whit3rd@gmail.com
wrote:

On Friday, May 24, 2019 at 4:51:24 AM UTC-7, DecadentLinux...@decadence.org wrote:

It was my understanding that CRTs ALL have magnetic field beam

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.

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.

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.