[tek 2246] single sweep purpose - Page 1
Forum section: electronics / testgear

author: cdc3oo
author_rank: Contributor
timestamp: December 10, 2022, 08:31:33 am
content: 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

author: David Hess
author_rank: Super Contributor
timestamp: December 10, 2022, 04:23:32 pm
content: Quote from: cdc3oo on December 10, 2022, 08:31:33 amThat is exactly what it is for, and the bezel has mounting rails for a camera. Single sweep applies to A mode also.

author: graybeard
author_rank: Frequent Contributor
timestamp: December 10, 2022, 04:32:36 pm
content: I have used single sweep to detect if a transient event has occurred.

author: dshorthill
author_rank: Contributor
timestamp: December 10, 2022, 05:37:37 pm
content: Typically used with Polaroid film.https://vintagetek.org/wp-content/uploads/2018/12/Tek-Camera-Brochure.pdf

author: TimFox
author_rank: Super Contributor
timestamp: December 10, 2022, 06:05:09 pm
content: 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.

author: David Hess
author_rank: Super Contributor
timestamp: December 11, 2022, 07:55:08 am
content: Quote from: graybeard on December 10, 2022, 04:32:36 pmTo detect transients, I typically use NORM mode which sweeps on every trigger, but unlike AUTO mode never free runs.Quote from: TimFox on December 10, 2022, 06:05:09 pmThey also made oscilloscopes with a blue phosphor which exposes the film even faster.

author: tautech
author_rank: Super Contributor
timestamp: December 11, 2022, 08:30:58 am
content: Quote from: David Hess on December 11, 2022, 07:55:08 amAh, 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 !

author: rf-loop
author_rank: Super Contributor
timestamp: December 11, 2022, 09:20:55 am
content: 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 P5But 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.

author: David Hess
author_rank: Super Contributor
timestamp: December 11, 2022, 10:57:12 pm
content: Quote from: tautech on December 11, 2022, 08:30:58 amYou 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.

author: TimFox
author_rank: Super Contributor
timestamp: December 11, 2022, 11:51:28 pm
content: 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.

author: David Hess
author_rank: Super Contributor
timestamp: December 12, 2022, 01:13:28 am
content: Quote from: TimFox on December 11, 2022, 11:51:28 pmThe 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:P31 Green Relative Luminance 100% Relative Photographic Writing Speed 50% Decay Med-ShortP11 Blue Relative Luminance 15% Relative Photographic Writing Speed 100% Decay Med-ShortP7 Blue Relative Luminance 35% Relative Photographic Writing Speed 75% Decay LongP7 is fluorescent in blue and phosphorescent in yellowish-green. P39 is a yellowish-green with a long decay for low refresh rate displays.

author: cdc3oo
author_rank: Contributor
timestamp: December 12, 2022, 12:20:39 pm
content: Big thanks to all of you for those very informative answers !!!

author: jonpaul
author_rank: Super Contributor
timestamp: December 12, 2022, 01:10:53 pm
content: mémoire1970s, 1980s, Tektronix 7000, 475B, dark room, scope hood, max intensityTrigger 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 EEJon