Author Topic: 2 inch video monitor  (Read 7285 times)

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Offline GK

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2 inch video monitor
« on: March 01, 2014, 08:35:18 PM »
It was a really nice sunny day today, so I decided to confine myself to the shed and build this. I picked up a number of "new old stock" 2AP1A, 2" cathode ray tubes a while ago and I've been itching to do something with them. This is my best attempt at a composite video monitor using bits that I could rummage from by junk box(es).

I'm using the specified maximum rated acceleration potential of 1kV for the 2AP1A. HT comes from a little universal hybrid linear/switching, variable-output PSU (the green PCB) that I originally designed for powering photo multiplier tubes, which had to be modified a little for this application.

The cathode is tied to a fixed potential and grid modulation is used. From a sample-and-hold type DC restorer the video amplification path is directly coupled to the CRT grid. Being a monochrome display, the chrominance component is separated (with an old passive hybrid/thick film Sony "Y/C module") from the luminance prior to DC restoration and amplification. All this results in the best possible quality picture.   

Don't have the time to draw out the schematic right now. I designed the thing as I went along and 90% the schematic hasn't been scribbled down.

Vertical and Horizontal raster deflection is provided by a pair of MJE340 long-tail pair amplifiers on a supply of +300V, delivering push-pull deflection voltages to the respective deflection plate pairs.

That's Mark Evans on the screen, assembling a Rover V8 - from  "A 4WD is Born".



« Last Edit: March 01, 2014, 08:41:24 PM by GK »

Offline mikeselectricstuff

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Re: 2 inch video monitor
« Reply #1 on: March 01, 2014, 09:03:26 PM »
Awesome!
Stuff like this has to be worth more than a gazillion lame Hackaday posts where someone connected an Arduino to something, or left a breadboard in a supposedly "finished" project  ;D
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Offline Psi

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Re: 2 inch video monitor
« Reply #2 on: March 01, 2014, 09:38:54 PM »
Seriously, that's amazing for a days work,

Actually that would still be amazing for a weeks work :P
« Last Edit: March 01, 2014, 09:47:38 PM by Psi »
Greek letter 'Psi' (not Pounds per Square Inch)

Offline GK

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Re: 2 inch video monitor
« Reply #3 on: March 02, 2014, 10:30:33 AM »
LOL, glad y'all like it.  :D

I've done quite a bit of video processing and have repaired and studied a lot of old oscilloscopes (a bit of a fetish of mine) so I pretty much new how to tackle the design beforehand.

I'll sit down and scribble down the schematic maybe later this afternoon.

Offline w2aew

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Re: 2 inch video monitor
« Reply #4 on: March 02, 2014, 10:49:03 AM »
LOL, glad y'all like it.  :D

I've done quite a bit of video processing and have repaired and studied a lot of old oscilloscopes (a bit of a fetish of mine) so I pretty much new how to tackle the design beforehand.

I'll sit down and scribble down the schematic maybe later this afternoon.

Yes, looks great! Much cleaner and crisper video than my simple NTSC to Scope converter circuit (used to make my avatar and a few of my videos). Looking forward to the schematic.  Nice manhattan construction too.
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Offline GK

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Re: 2 inch video monitor
« Reply #5 on: March 02, 2014, 01:25:19 PM »
Yes, looks great! Much cleaner and crisper video than my simple NTSC to Scope converter circuit (used to make my avatar and a few of my videos). Looking forward to the schematic.  Nice manhattan construction too.



You will notice some similarity in the deflection circuitry  ;)

For the best quality monochrome picture you really need to filter out the chroma component and DC restoration of the video signal helps a lot. Without the latter the black level does not remain at a fixed level, but varies up and down along with the average intensity of the display.   

I don't have the schematic for the HT regulated supply module immediately at hand, as that was originally designed at work.




Offline T3sl4co1l

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Re: 2 inch video monitor
« Reply #6 on: March 02, 2014, 01:32:05 PM »
Nice!

I made one quite some time ago, with a magnetic deflection CRT... should pull it out again some time and play.  Although without any NTSC floating around anymore, there isn't much to display on the thing...

http://youtu.be/9-y8fXgMx3w

Think I later took a picture of a reasonable raster, though I didn't have enough voltage to get full width or brightness.

Tim

Offline w2aew

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Re: 2 inch video monitor
« Reply #7 on: March 02, 2014, 02:22:17 PM »
Yes, looks great! Much cleaner and crisper video than my simple NTSC to Scope converter circuit (used to make my avatar and a few of my videos). Looking forward to the schematic.  Nice manhattan construction too.


You will notice some similarity in the deflection circuitry  ;)

For the best quality monochrome picture you really need to filter out the chroma component and DC restoration of the video signal helps a lot. Without the latter the black level does not remain at a fixed level, but varies up and down along with the average intensity of the display.   

I don't have the schematic for the HT regulated supply module immediately at hand, as that was originally designed at work.

Nice. I like the DC restoration circuit with the S/H.
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Offline Rigby

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Re: 2 inch video monitor
« Reply #8 on: March 02, 2014, 04:05:09 PM »
cripes, that is awesome.

Offline GK

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Re: 2 inch video monitor
« Reply #9 on: March 02, 2014, 04:39:59 PM »
Nice. I like the DC restoration circuit with the S/H.


The implementation is mine but the concept is an old one.

Offline GK

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Re: 2 inch video monitor
« Reply #10 on: March 02, 2014, 04:43:14 PM »
there isn't much to display on the thing...


The plan is to build a refined/expanded version of this into a 2U rack case for a transmitting rack, to connect to a dedicated receiver and thus act as a "side tone" monitor for ATV transmission.

 

Offline pickle9000

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Re: 2 inch video monitor
« Reply #11 on: March 02, 2014, 04:53:52 PM »
Just one more awesome!

Offline marshallh

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Re: 2 inch video monitor
« Reply #12 on: March 02, 2014, 05:10:43 PM »
Well, I'm just going to hang it up now. I'll never be this awesome
17:31 < c4757p> I've never seen anything covered in words like "Arduino" and "maker" that was a good example of proper design
11:37 <@ktemkin> c4757p: marshall has transcended communications media
11:37 <@ktemkin> He speaks protocols directly.

Online vk6zgo

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Re: 2 inch video monitor
« Reply #13 on: March 02, 2014, 06:24:54 PM »
Reminds me a bit of the 5" TV I made years ago,using a 5BP1.

It was already years after such things were worth making,some of the valves(tubes) in the original design weren't available,so I made (not so appropriate) substitutions.

It worked,on one occasion--I saw the end of a movie,but it still had a lot to do to finish it off.
I lost interest,& never did that work,so it ended up being pulled apart for bits.

Offline megajocke

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Re: 2 inch video monitor
« Reply #14 on: March 03, 2014, 09:16:06 AM »
Cool!


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