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Old 27th Jan 2022, 8:06 am   #1
Derfix0
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Default CRT capture method?

Hi, I have just bought a CRO but my question is about the CRT so thought I should put it here.
Is it possible to splice into the inputs going into the CRT and devise a capture method?
Or is it possible by another method?
Thanks in advance
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Old 27th Jan 2022, 10:13 am   #2
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Default Re: CRT capture method?

What is it you want to do? Produce a digital image of the screen?
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Old 27th Jan 2022, 11:07 am   #3
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Default Re: CRT capture method?

There are several ways you can go.

The most used in the day was to use a camera. Various firms made cameras specifically to fit onto popular makes of scope. HP's 197A had a UV illuminator to make the screen glow a little to show up the graticule, and took Polaroid film packs. There was no exposure metering so you set things on guess-and-hope until you'd built up some experience. Polaroid film was expensive. It is now very expensive and difficult to find.

Some makers made analogue scopes with sampling systems to produce a low speed plot that could go either to an external X/Y plotter, or to a built-in paper-roll printer. One of these nowadays would be a serious restoration project.

Then we come to digitising scopes. Some will drive an external printer, a few include printers.

Finally there are test executive softwares which can drive digital scopes and extract data, format as you wish and drive printers, make image files, whatever you want. But these things are capable of much more, and priced for it.

Trying to put your own digitiser or sampler onto an existing scope would be a massive design undertaking, and whatever you did would load the Y amplifier chain, affecting its performance. The amount of effort and time involved, if applied to most jobs would earn you enough money to buy a modern digitising scope and a printer and software! I don't imagine anyone going this route other than through seeing it as a challenge.

If you just want to record things on the screen, the camera route is the quickest and cheapest. You just need some bench space and a mini tripod for a fairly pedestrian digital camera. Cast-off digital cameras are almost worthless once they are no longer at the current number of megapixels, and yet will have plenty of resolution for this job.


Oh, and you can also zoom out or pull back to get a photo of the scope control settings!

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Old 27th Jan 2022, 9:02 pm   #4
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Default Re: CRT capture method?

I happy with the results I get with a hand-held camera or mobile phone.
Dimming the room lights to avoid reflections is all I do really.
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Old 27th Jan 2022, 11:05 pm   #5
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Default Re: CRT capture method?

Likewise. I invert the image for printing a hard copy to get black lines on a white background. Using my now ancient Pentax Optio 330 digital camera I have simply pointed it at the screen using the close-up setting, or, if a single trace was needed, used its night setting (the closest it has to a "B" shutter speed, where it makes a 10 second exposure) and the single shot function on my scope. Knocking up a hood to cut out ambient light reflections might be needed: cardboard is fine for the occasional use.

In my days at Plessey in the 1970's we used 'scope cameras which took Polaroid black & white roll film.
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Old 29th Jan 2022, 1:35 am   #6
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Default Re: CRT capture method?

Have only needed to do this once in fairly recent years, used a standard 35mm cameral with remote shutter release and a home made light shield of black painted cardboard.
Used special monochrome film called "high contrast" that was primarily intended for document copying, this gave a much better image than standard film intended for "half tone" views of people or buildings etc.

The developed negatives could be viewed directly, or projected without any need to print them.

The high contrast film was very easy to develop, I managed it fine with very little experience of such work.

Better resolution photos could be achieved with an old style large format camera, but that needed expensive film and a proper photgrapher rather than me.
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Old 30th Jan 2022, 3:15 pm   #7
Derfix0
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Default Re: CRT capture method?

Wow, didn’t expect this many replies lol.
The only problem with taking a photo is I don’t have a proper camera, I’ve only got my phone with the stupid roller shutter thing and when I’ve tried it won’t come out right.
Is it possible to tap into the feeds and give them to like a capture card
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Old 30th Jan 2022, 5:01 pm   #8
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Default Re: CRT capture method?

Phone cameras are rarely any good unless you buy a stupidly expensive phone.
I use a bargain basement hand held digital camera. It is just fine.
You had to have a special adapter for film cameras but they are no longer for scope traces.
If you want cheap capture a desktop computer will do it with a USB scope adapter.
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