[tek 2246] single sweep purpose

[cdc3oo]

Hello dear EEV members,

Sorry for this dumb question but I want to get some clarification.

I recently got a 2246, cleaned, checked, lowered fan noise. It looks mint, works well and I really like it.

I am puzzled about trigger single sweep mode: since there is no memory, am I right if I assume this feature was designed to allow shooting with a film camera setup in B mode ?

Thank you

[David Hess]

I am puzzled about trigger single sweep mode: since there is no memory, am I right if I assume this feature was designed to allow shooting with a film camera setup in B mode ?

That is exactly what it is for, and the bezel has mounting rails for a camera.  Single sweep applies to A mode also.

[graybeard]

I have used single sweep  to detect if a transient event has occurred.

[dshorthill]

Typically used with Polaroid film.

https://vintagetek.org/wp-content/uploads/2018/12/Tek-Camera-Brochure.pdf

[TimFox]

Back in the day, Polaroid made an ASA 10,000 film specifically for oscilloscope recording.
Their ASA 3,000 film had reasonable control on the speed, but the ASA 10,000 film was really a minimum spec.
Analog oscilloscopes had a "writing speed" specification for this use.

[David Hess]

I have used single sweep  to detect if a transient event has occurred.

To detect transients, I typically use NORM mode which sweeps on every trigger, but unlike AUTO mode never free runs.

Back in the day, Polaroid made an ASA 10,000 film specifically for oscilloscope recording.
Their ASA 3,000 film had reasonable control on the speed, but the ASA 10,000 film was really a minimum spec.
Analog oscilloscopes had a "writing speed" specification for this use.

They also made oscilloscopes with a blue phosphor which exposes the film even faster.

[tautech]

They also made oscilloscopes with a blue phosphor which exposes the film even faster.

Ah, I often wondered why. My first a Telequipment D83 made after Tek had acquired them apparently used a 7603 CRT which when right had the nicest sharp blue traces you ever did see. 

A HP1740 I had the same time had green traces that I never liked as much yet I now prefer green with a DSO, go figure ! 

[rf-loop]

Gentelemen.

Attached 8 pages pdf.   It shows a little what kind of different properties different "few" CRT tube phosphors have.

As an example, on page 2 Tektronix's very fast blue P5

But if you read more you can see that there is also many many kind of "blue" or "bluish" phosphors.
Also there is phosphors what may have extremely long persistence... days and even more for special purposes.
Also good to note there are phosphors what change color during persistence time. So user can see traces "age" on screen.

Many phosphors have also been aimed at very long persistence times for various purposes. A single shot with a very long persistence phosphor is quite different from a short one.
For different purposes, both the activation speed and the persistence time may need to be optimized for the purpose of use. (I don't mean the so-called memory tubes where the persistence time had to be adjusted as well) Different oscilloscopes were also chosen for different purposes with different phosphors. It was not driven by chance or fashion.
Yes, they were carefully thought out for different uses. So, if you don't like some phosphorus, the reason might also be that you don't use it for the purposes or in the way it was designed. You can also learn some things from old HP Journals. Of course, there are only the so-called "general models" and then there were also the usual cheap ones where the idea was to just put the cheapest possible display tube.

[David Hess]

They also made oscilloscopes with a blue phosphor which exposes the film even faster.

Ah, I often wondered why. My first a Telequipment D83 made after Tek had acquired them apparently used a 7603 CRT which when right had the nicest sharp blue traces you ever did see. 

You have to be a little careful about CRTs with the most common P31 green phosphor which can very between something like sky blue and green.  The only thing I know is that it does not depend on CRT acceleration voltage.  I have a pair of 7834s which are otherwise identical and one is greener and one is bluer.

My 7603 was in storage for 20 years and after I left it on for a couple of days accidentally, the sharpness of the CRT noticeably improved.  I think there is a mechanism in the CRT to scavenge gas and ions during normal operation.

[TimFox]

The P7 phosphors have very long persistence, with a second phosphor (excited by light from the prompt first phosphor layer) persisting for roughly a minute in dark light.

[David Hess]

The P7 phosphors have very long persistence, with a second phosphor (excited by light from the prompt first phosphor layer) persisting for roughly a minute in dark light.

The older Tektronix catalogs have details about the various phosphors, but I never found anything to explain why some P31 phosphor is bluer and some is greener.

Code: [Select]

P31   Green   Relative Luminance 100%   Relative Photographic Writing Speed  50%   Decay Med-Short
P11   Blue    Relative Luminance  15%   Relative Photographic Writing Speed 100%   Decay Med-Short
P7    Blue    Relative Luminance  35%   Relative Photographic Writing Speed  75%   Decay Long
P7 is fluorescent in blue and phosphorescent in yellowish-green.  P39 is a yellowish-green with a long decay for low refresh rate displays.

[cdc3oo]

Big thanks to all of you for those very informative answers !!!

 

[jonpaul]

mémoire

1970s, 1980s, Tektronix 7000, 475B, dark room, scope hood, max intensity

Trigger DUT,  eyes  glued to the scope hood, shot, repeat.....

Many happy hours working on HV pulse transformers, arc lamp ignitors, radar pulser, transient generators.

Had tektronix  scope cameras triggered to the sweep on 7000 scopes, used Polaroids.

just the ramblings of an old retired EE

Jon