NBTV Television Analyst

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NBTV Television Analyst

Postby Harry Dalek » Sun Mar 29, 2020 3:52 pm

Some thing i have always liked is the Television Analyst a device used in the past by TV service men to use to adjust the Televisions they were repairing ...
Back in the day if they go up early and did their adjustments then i am sure there would of been a few Test cards broadcast ,perhaps the poorer repair men had to do this :wink:
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The idea here is to make a 2 CRT device again one crt is the monitor tossing up if this monitor can this time switch between a dual monitor and a scope and the 2nd CRT is a Flying spot scanner for a multi system test card video signal ..unlike the original shown above this one will do NBTV .

Well i am not happy unless i have something to think about ! so this is the next project to keep me busy for the next few months and Thanks to Andrew once again i still have a abundance of CRTS very much so the 3Bp1 also cases for the size of this CRT are not easy to come by but i have something .

Since i have more 3Bp1's than other types 2 of these will be used once again and don't worry the last 2 CRT project the binocular is safe and sound in a box out of the way for now ,but looking at what junk i have laying around in my shed i found a old DVD player case just the right size .
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Worked out the best place to mount the viewing CRT the slot where the dvd player was i will use as a panel
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Its more along since than this photo the CRT bezel is bolted on now
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On the Flying spot scanner side i could use a PMT as original but i think from my experiments in the past on NBTV light transmission if i can do this with an led and a solar cell a CRT and a solar cell should work also ..space and power supply make it a better idea to me .

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So the Flying spot scanner is some thing i am still thinking about but i think i will mount it about there.

What i would like it to do is make it an easier video generator monitor for NBTV limited i suppose to how small a raster dot the Crt can do for a correct result so it should be able to do a few line rates.

I just really need a few zener diodes pretty much have nearly every thing else for this for this ,and need to do this like with all CRT projects carefully and safely .
EDit
35mm slides for the FSS idea so far i may project focus the CRT raster to the slide for higher definition scan see how the optics go when i get there .
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Re: NBTV Television Analyst

Postby Klaas Robers » Sun Mar 29, 2020 8:35 pm

Harry, you need quite some space in front of the flying spot CRT. If you look to the first photo in your posting, you see left of the CRT a Printed Circuit Board with a radio tube, which is a photo multiplier. I guess that you need at least a distance equal to the diameter of the screen. And place the slide as close as possible to the surface of the screen. This is because the system uses so called "proximity focus", that will say no focus at all.

For a good flying spot scanner you should use a CRT with short persistence, mostly blue phosphor.
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Re: NBTV Television Analyst

Postby Harry Dalek » Sun Mar 29, 2020 10:41 pm

Klaas Robers wrote:Harry, you need quite some space in front of the flying spot CRT. If you look to the first photo in your posting, you see left of the CRT a Printed Circuit Board with a radio tube, which is a photo multiplier. I guess that you need at least a distance equal to the diameter of the screen. And place the slide as close as possible to the surface of the screen. This is because the system uses so called "proximity focus", that will say no focus at all.

For a good flying spot scanner you should use a CRT with short persistence, mostly blue phosphor.


Hi Klaas i was not planning on using a PMT ,but a solar cell instead the FSS side of it is not set in stone or its position or proximity focus which was the first idea ,i was thinking of 35 mm slides which i have used before for NBTV flying spot scanning but with a PMT so i have a good idea what works and doesn't on this idea .
I have also used light transmitter to solar cells so on this side i also have an idea that it should work as a simple replacement for a PMT .

I was thinking as well the proximity idea is very simple crt raster dropped to the size of the slide ...slide on the crt face and solar cell behind pick up the light .

Sort of done all this before but with a PMT and used my scope for the NBTV raster .

The scope green CRT still worked fine when using the PMT last time tried did not seem to fussed with the green light images turned out pretty good once i worked out i had to get the slide or transparency butted up to the crt face no distance .

But yes if i were using a PMT it needs a bit of distance or as i recall it gets over loaded but you can have it some distance from the CRT for it to still work and in room light too ...just have to adjust the negative voltage to it for different room light levels as the extra light effects it .

But this time a Solar cell for the Harry NBTV Analyst !
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Re: NBTV Television Analyst

Postby Klaas Robers » Mon Mar 30, 2020 3:38 am

If you use a larger solar cell, then it doesn't work any way. Because seen from the detector, the light spot on the tube should be able to hide behind a small spot on the slide. I think also that for the set-up of your first photo, there should have been an opaque plate with a small hole just before the PMT. That then is the "eye" of the light sensor. If the light sensitive area is larger, the light of the CRT-spot always can find a route around a small dot on the slide. And then the resulting picture is unsharp.
I hope that this makes clear to you how the flying spot system works, to get a sharp picture.

In fact I don't believe any way in proximity focus. I fear that the second photo that you sent is fake. With proximity focus you cannot have a sharp picture for standard definition TV.

Of course the space between the CRT and the PMT should be absolutely dark. I don't know how they obtained that in photo 1, may be that the cabinet was absolutely closed when it was operated.

In our 1970 TV-studio at Philips Research Lab (Nat.Lab.) we had a flying spot scanner for slides. But we had a lens that made a sharp image of the CRT-screen onto the slide. So when you could look at the surface of the slide, you saw a sharp spot of light that scanned the slide. Then there was a colour splitting prism and 3 photo multipliers for Red, Green and Blue. There was no lens between the slide and the PMT's. But we obtained razor sharp pictures in 625 lines PAL.
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Re: NBTV Television Analyst

Postby Harry Dalek » Mon Mar 30, 2020 7:21 pm

Klaas Robers wrote:If you use a larger solar cell, then it doesn't work any way.


Hi Klass what you are saying is a solar cell will not pick up the raster i am confused i must be mistaking your meaning here ...

Because seen from the detector, the light spot on the tube should be able to hide behind a small spot on the slide.


Well the set up is CRT /slide /then PMT or solar cell

The PMT experiments below

I will post up my flying spot experiments link below ,they have dropped our internet speed due to all the people home because of the virus ...or i would post up some pictures but i am lucky to type a message at the moment .
So if you look on the first page that was my set up at first and results ...my mistake was the distance of the CRT from the slide so results were blurred

https://www.taswegian.com/NBTV/forum/vi ... =31&t=2467


I think also that for the set-up of your first photo, there should have been an opaque plate with a small hole just before the PMT.


The Television Analyst all seem like that set up i will look and check if my interest speeds up again !

That then is the "eye" of the light sensor. If the light sensitive area is larger, the light of the CRT-spot always can find a route around a small dot on the slide. And then the resulting picture is unsharp.


Depending on the slide size i used i adjusted the raster to the size of that slide i know what you mean from your comment ...most of my results on that link are not in great focus still as i have the plastic screen between the slide and the CRT a mm or so thickness in the plastic but its still enough to stop a good focus.
If any thing it gave me a good idea of what works in this set up and what doesn't...towards the end i was able to do projection CRT live scanning via that lens .
I enjoyed that project reason i am trying something similar now .

I hope that this makes clear to you how the flying spot system works, to get a sharp picture.


Help is always welcome Klaas !

In fact I don't believe any way in proximity focus. I fear that the second photo that you sent is fake. With proximity focus you cannot have a sharp picture for standard definition TV.


I know i have a video up on this unit lid off in action it seem very similar to how it worked for me so long as the slide or transparency was butted up as close to the CRT the focus of that raster scanning the slide image was in focus ,distance of the PMT just adjusted for best results .

Of course the space between the CRT and the PMT should be absolutely dark. I don't know how they obtained that in photo 1, may be that the cabinet was absolutely closed when it was operated.


For the weak projection CRT flying spot tests i think i posted up on the last page of page 2 of that link that is correct has to be dark only due to the weak raster light and you have to increase the PMT voltage for me it was around 700 volts ....but i have to say klaas this is not correct on slide set ups even that TV Analyst with the lid open will work you can get results in room light ...the key is ...the voltage applied to the PMT the PMT is pretty much run on its minimum data sheet voltage 200 or 300 volts or the light would over load it as you think .


In our 1970 TV-studio at Philips Research Lab (Nat.Lab.) we had a flying spot scanner for slides. But we had a lens that made a sharp image of the CRT-screen onto the slide.


Arrr good to know that was one of my ideas for this ,i was not sure i would have the room for the lens distance to to the slide where i want to put it ...but its nice to know it was done !


So when you could look at the surface of the slide, you saw a sharp spot of light that scanned the slide. Then there was a colour splitting prism and 3 photo multipliers for Red, Green and Blue. There was no lens between the slide and the PMT's. But we obtained razor sharp pictures in 625 lines PAL.


OH that sounds like a beautiful set up i really like that idea for colour ! i wish you had photos ...very very interesting .

I think this is the video my internet is so slow to view it correctly of one with the lid open


youtu.be/LF9bckHvfhA
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Re: NBTV Television Analyst

Postby Harry Dalek » Mon Mar 30, 2020 10:38 pm

MY son William and me 2 years ago Flying spot CRT projection tests ,pretty much scope crt with NBTV raster to a lens and focusing that lens on us in the dark PMT pointed at us and voltage on PMT high mid 600 volts


youtu.be/3a2diHwDoeU



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Re: NBTV Television Analyst

Postby Harry Dalek » Tue Mar 31, 2020 7:51 pm

OK my thoughts are now on powering the tubes and how to do this ...i of cause thank Steve A once again for another project using mostly what came from he's mind for me all i have to do is not make a mistake :wink:

Today getting some zener diodes i needed and panel nobs switches i think i am ready to construct the parts needed to circuits ...as usual the HV power supply is always a good starting point
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I am of cause using the the old adage if it ain't broke don't fix it i am using what i know works and as usual just re purpose it for a new use but there are new ideas here i have to work out .
Tossing up the idea of the two crts can share each others the deflection plates and deflection amplifiers does mean what ever i am scanning size wise will be mimicked if i go down that road thinking if this is a good thing less circuit bad monitor raster screen size might be a little small on 35 mm slides...thinking about this

Also on this CRT schematic below i will use the one as shown for testing the brightness just as just for the flying spot crt the other i will use in monitor mode so not use the opto trimmer pot for brightness .

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As always one step problem at a time first i need power for those Crt's work on the power supply next day or 2 .
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Re: NBTV Television Analyst

Postby Klaas Robers » Wed Apr 01, 2020 6:25 am

Yes Harry, those pictures were really unsharp. It was just visible what it was, no more than that. If you place a black opaque hood over the PMT, and drill a small hole that "looks" to your slide, then you might get a sharper picture. And yes of course, the pinhole will make the output signal lower. But the PMT is sensitive enough if you increase the supply voltage.

Any way you should increase the space between the PMT and the slide, and make the space between the slide and the flying spot tube as small as possible.

And make a black tunnel between the pinhole and the transparent part of the slide, such that the pinhole sees only light from the slide. It is not impossible that such a tunnel was also part of your first photo, but that it was removed for making the photo.

Realize yourself that when you make the raster on the CRT larger and smaller, that you zoom the picture, and if you shift the scanned raster that you can do pan and tilt.
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Re: NBTV Television Analyst

Postby Harry Dalek » Wed Apr 01, 2020 7:57 pm

Klaas Robers wrote:Yes Harry, those pictures were really unsharp.


Yes the first tests were very blurry Klaas there's always a reason and it was because i placed the Slide on the oscilloscopes" graticule" the plastic grid infront of the CRT the cathode ray tube was sitting not even flush with that but a few cm behind no wonder ! as shown in image below ...
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At the end last postings i didn't want to remove the Graticule so i just did the best i could do with out doing damage to my old scope and just moved the CRT to touch the back of the plastic Graticule that improved the focus not 100% (as the Graticule plastic is thick) but it would of been if i could of placed the side direct on the screen its self so for me it showed how this works using this method improvement evidence below ..

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If you place a black opaque hood over the PMT, and drill a small hole that "looks" to your slide, then you might get a sharper picture. And yes of course, the pinhole will make the output signal lower. But the PMT is sensitive enough if you increase the supply voltage.


Am i correct Klaas in the drawing below from your description ? i can only think this is a similar idea to a pin hole film camera where as the tiny hole i suppose replaces a lens and as you say reduces the light ..i can't say i have seen the idea used in the American 525 line Television Analyst's ...i will have another look but as i recall the PMT's are as is just pointed at the screen slide i know they run around the 300 400 volt range on their PMT's so running on a lower end of the data sheet range .
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I never understood why they used a PMT with the amount of light from a CRT you would not need something as sensitive as a PMT reason i was thinking why not use a Solar cell as such ?
My idea was to use one of these 2 ideas on the solar cell side ? i did some drawings below just to make it clear that i know you think this will not work ?
I have PMTs its no big fuss i just thought this would be a neater idea cutting down on the electronics and space in the case ..i am listening just curious !
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Any way you should increase the space between the PMT and the slide, and make the space between the slide and the flying spot tube as small as possible.


This might be a problem but i have been thinking down those lines if i went down this road ,as to where my mounting of the CRT is now i was thinking pointing the Crt at a mirror slight angle the PMT mounted along side of the case perhaps ...sorry my drawings as a bit rushed !

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And make a black tunnel between the pinhole and the transparent part of the slide, such that the pinhole sees only light from the slide. It is not impossible that such a tunnel was also part of your first photo, but that it was removed for making the photo.


I was enclosing the the CRT and light sensitive device in the case which should be light proof but i will keep that idea in mind .

Realize yourself that when you make the raster on the CRT larger and smaller, that you zoom the picture, and if you shift the scanned raster that you can do pan and tilt.


As i recall with the scope i could zoom in part of the image in low def of cause ...i rather enjoyed the effects you mentioned also when adjusting this on the oscilloscope raster display viewing the results on the PC monitor ...

Thinking a lot here on the FSS side ,really only up to The power supply at the moment which i will start on tomorrow if the Transformer i am using works out .
Thanks for taking an interest Klaas i respect your input !
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Re: NBTV Television Analyst

Postby Steve Anderson » Wed Apr 01, 2020 8:48 pm

I haven't read through all of the above postings thoroughly but there's an element where the persistence of the CRT phosphor can play a part. What is needed for a slide scanner is a very short persistence CRT - the opposite of a P7. A P1 (a general purpose green CRT phosphor) won't cut it. The decay in the light output is too slow, even at NBTV rates. The result is smearing and generally poor resolution.

Either a shorter persistence CRT is required or the image is scanned at very low rates and then sped up to generate the final image - not very practical. Our eyes may not see it, but the PMT (or whatever) certainly does. The reason P1 phosphors were used is 1) The sensitivity of our eyes to the green part of the spectrum, 2) The afterglow of a few milliseconds assists in the same.

PMT's are generally most sensitive in the blue end of the spectrum, a perfect match for a short-persistence blue CRT. There were CRT's designed for this very purpose that had a phosphor that emitted not only blue but UV. Only good for monochrome slides only.

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Television Analyst The Transformer

Postby Harry Dalek » Wed Apr 01, 2020 9:10 pm

Looking for a Transformer this i have found in my collection from an 80s laser disk player ones with a helium–neon laser
It has a supply for the CRT heaters and windings for a dual 12 volt supply,but the high voltage only has 2 winding's , i need to double check the results here i think the voltage is pretty high i will replace the batteries in my multimeters so know for sure .
I do like the copper shielding which i think is for lowering the transformers magnetic field ? and it does fit the case as well .
If i go with this one i think i will need just to double or triple the voltage ...well this is the first choice so far .

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Re: NBTV Television Analyst

Postby Klaas Robers » Wed Apr 01, 2020 10:36 pm

Yes Harry, in fact you make a pinhole camera for the PMT. A pinhole is a lense with an undefined focus distance. So the pinhole makes a sharp image of the slide AND of the CRT-screen at the same time. A pinhole photo camera makes snapshots that are always sharp.

The idea of the mirror is not bad, however also for the mirror you need space in front of the CRT-screen.

Your original idea of a solar cell against the slide, drawing 2 and 3, does not work. Consider a white slide with a small black spot on it. When the light spot on the CRT is positioned just below the black spot, light of the CRT will shine around the black slide spot and illuminate the solar cell on other places. That is the reason that you will get an unsharp picture. Only large black areas will hide the CRT-spot almost completely.

The size of the pinhole close before the PMT defines the sharpness of your resulting picture. Something to experiment with.

The fourth drawing that you made is how we used the Flying spot in our Colour TV studio at the Nat.Lab. We had a disc with 20 slides. The avatar that I have, the lady with the roses, was one of those slides. The EBU, European Broadcast Union, had made about 15 of those slides, that were all well known by the experts, so they could judge the colour reproduction of the new TV-sets. On a certain moment, when the studio manager was cleaning up, I got a set of those slides.

The persistence of the CRT is also a point, very good Steve. However, if it is not too long, you can compensate for it in the video amplifier. And indeed blue phosphors have a much shorter afterglow. I have seen flying spot scanners for SSTV that used a P7 CRT and placed a blue filter somewhere in the light path. Then they used only the short persistence blue phosphor and discarded the yellow long afterglow.
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Re: NBTV Television Analyst

Postby Harry Dalek » Wed Apr 01, 2020 10:42 pm

Steve Anderson wrote:I haven't read through all of the above postings thoroughly but there's an element where the persistence of the CRT phosphor can play a part. What is needed for a slide scanner is a very short persistence CRT - the opposite of a P7. A P1 (a general purpose green CRT phosphor) won't cut it. The decay in the light output is too slow, even at NBTV rates. The result is smearing and generally poor resolution.

Either a shorter persistence CRT is required or the image is scanned at very low rates and then sped up to generate the final image - not very practical. Our eyes may not see it, but the PMT (or whatever) certainly does. The reason P1 phosphors were used is 1) The sensitivity of our eyes to the green part of the spectrum, 2) The afterglow of a few milliseconds assists in the same.

PMT's are generally most sensitive in the blue end of the spectrum, a perfect match for a short-persistence blue CRT.

Steve A.



Hi Steve
mmmm That is a problem i was thinking a solar cell pick up might be a better idea ,but i have used the PMT green scope tube idea here before and did not seem to bad at the time only problem i had on the slide idea was i couldn't place the side on the crt face so i was always a touch out of focus due to the space between the oscilloscope Graticule and the crt face ,considering i was scanning a 35mm side in 32 and 64 line results were pretty good.

I did know of the problem but not so much for NBTV till now ,but i would say it was impossibly bad/
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Re: NBTV Television Analyst

Postby Harry Dalek » Wed Apr 01, 2020 11:07 pm

Klaas Robers wrote:Yes Harry, in fact you make a pinhole camera for the PMT. A pinhole is a lense with an undefined focus distance. So the pinhole makes a sharp image of the slide AND of the CRT-screen at the same time. A pinhole photo camera makes snapshots that are always sharp.


I have never tried it for a PMT now i understand that sounds like a good plan ...i will use it . the PMT i was using last time with the lens had a iris i could adjust ...it might not of got small enough but i never checked if it effected focus either ..any case pin hole PMT sounds good to me .

The idea of the mirror is not bad, however also for the mirror you need space in front of the CRT-screen.


This is true to get the correct angle i have to see if its possible with this CRT's size i have smaller ones but i was going logically using 2 of the same CRTs means same power supply needs .

Your original idea of a solar cell against the slide, drawing 2 and 3, does not work. Consider a white slide with a small black spot on it. When the light spot on the CRT is positioned just below the black spot, light of the CRT will shine around the black slide spot and illuminate the solar cell on other places. That is the reason that you will get an unsharp picture. Only large black areas will hide the CRT-spot almost completely.


OK i will not bother with that idea if a solar cell s no good answers my question why they were not used in something like this ..


The size of the pinhole close before the PMT defines the sharpness of your resulting picture. Something to experiment with.


I was wondering about the hole size ,be nice to experiment i would like to know how this effects it i find that interesting .

The fourth drawing that you made is how we used the Flying spot in our Colour TV studio at the Nat.Lab. We had a disc with 20 slides. The avatar that I have, the lady with the roses, was one of those slides. The EBU, European Broadcast Union, had made about 15 of those slides, that were all well known by the experts, so they could judge the colour reproduction of the new TV-sets. On a certain moment, when the studio manager was cleaning up, I got a set of those slides.


Oh i see ,a five finger discount as they say :wink: were they all ladies flowers you might have all that's left ?

The persistence of the CRT is also a point, very good Steve. However, if it is not too long, you can compensate for it in the video amplifier. And indeed blue phosphors have a much shorter afterglow. I have seen flying spot scanners for SSTV that used a P7 CRT and placed a blue filter somewhere in the light path. Then they used only the short persistence blue phosphor and discarded the yellow long afterglow.


Steves remarks did worry me but for this learning exercise it will be good enough to keep me busy ..BTW a colour filter in the light path could improve things ? yes that reminds me about SSTV Fly spot scanning !
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Re: NBTV Television Analyst

Postby Harry Dalek » Thu Apr 02, 2020 6:05 pm

The mirror idea might just work i do have just enough room to angle a mirror a scrap plastic mirror shown .
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Looking at the transformers High voltage winding today its pretty near 900 volts that's looking at it on 3 multi meters ...would be fine for the PMT and CRTS ,over twice as high for the Positive CRT Anode ...wish it was a bit lower be perfect...

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Testing on a simple diode 3 capacitor hooked up in series the voltage jumps up high then starts to drop back ...not a good thing ...i tried then adding load resistor and one very high resistor between the transformer and diode and it then worked and voltage seems to stay at around 1600v using 3 caps at 450 volts each it would still need another to be safe i was not expecting such a high voltage and with the resistor in the way ...voltage readings seem about the same on the meters ...i am a bit iffy about the readings ...any case should be a negative version of this to be of any use if the voltage reading is accurate which it seems to be .
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The electromagnetic spectrum has no theoretical limit at either end. If all the mass/energy in the Universe is considered a 'limit', then that would be the only real theoretical limit to the maximum frequency attainable.
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Harry Dalek
"Fester! Don't do that to 'Thing'"
 
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