NBTV Television Analyst

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Re: NBTV Television Analyst

Postby Harry Dalek » Thu May 21, 2020 11:29 am

I am using the opto coupler circuit with out the 4066 for now..shown below with another club circuit for later on adding sync to the video signal , but i will replace that with the video inverter for this monitor .
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Last edited by Harry Dalek on Thu May 21, 2020 2:04 pm, edited 1 time in total.
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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Re: NBTV Television Analyst

Postby Harry Dalek » Thu May 21, 2020 2:01 pm

Ok the inverted video is sorted Thanks Steve Klaas your circuits keep on giving .
I will have a look next here at the negative supply for the PMT i will end up having 3 tubes working off this same HV supply here .

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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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Re: NBTV Television Analyst

Postby Harry Dalek » Sun May 24, 2020 10:05 pm

Well i was hoping to get this PMT to work by now but 2 days of testing i found it is light sensitive to a point but when i did a light transmitting test in its light proof chamber i found instead of a nice waveform all i was getting was spikes no matter the voltage to the PMT or transmitting level .
I was trying a test similar to here below same 3 colour light transmitter

I was using as in the tests One of Steves reversing bars

viewtopic.php?f=31&t=2403

I think i have picked another dud PMT :roll: ,i do have one handy that's is fine which i used before as a last resort but i still have another 2 PMTs to try before that stage .

So looks like the next one to hook up and see is the one i was going to pick the first time around The Hamamatsu R1282 has a wide Colour working range .

I will try again this week every thing is done just need the PMT to cooperate.
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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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Re: NBTV Television Analyst

Postby Harry Dalek » Thu May 28, 2020 4:00 pm

Sorry for the delay a lot of head scratching as 2 PMTS pretty much seem dead i don't know why or how ...tried them twice now both seem to have no light sensitivity at all ..no idea of the history to their use so seems they were killed at some point by someone .

I had to also set up the transmitting circuit and head amp to make sure they was not at fault so checking with the known working RCA pmt it worked fine with the light detection NBTV 3 colour led transmitter top 2 photos .

I went back then to the 3 PMTS i was trying out 2 were a waste of time but again the 92521 with yellow tape is working its a lot more sensitive to the blue light than Green but does still work on the green over all the RCA is the best PMT out of the 2 .

Sorry for the poor shots very rushed today ..

Now i know 2 of them work for sure there's no reason either of these two PMTS can't pick up the flying spot CRT ,i will try them out tomorrow ... :roll:
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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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Re: NBTV Television Analyst

Postby Harry Dalek » Fri May 29, 2020 8:11 pm

Today had no problems here transmitting NBTV via the Led transmitter pick up to the PMT showing result via the front panel CRT.
Think here i was trying a pin hole of light to the pmt it was on -1000v so i was pushing it also with the extra room light .
Didn't have much luck via the flying spot CRT yet only shadows but was unable to cut out room light noise so i will do some night work cut out the natural light factor so i just have the CRTs going ,i can also adjust it that way with the lid off .

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Re: NBTV Television Analyst

Postby Harry Dalek » Sat May 30, 2020 4:33 pm

I found this interesting using pin hole focusing for a CRT ..
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Re: NBTV Television Analyst

Postby Harry Dalek » Wed Jun 03, 2020 1:16 pm

With the long delay between posts i have been trying different experiments with the PMT as it should work but it isn't as far as the camera side pointing it at a slide on the crt ,so i wanted to track down the problem before posting up .
Since i had a working system from a few years ago i pretty much used this to repeat the working result and used it to track down where i have the problem .
Got my old scope out again to display the raster i wanted the exact system not the new scope .. i used it before so got also the portable PMT Flying spot camera out and pointed it at this scope and worked right away i can even see the oscilloscope graticule lines .
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Putting a screw driver infont of the slide and my finger in this video slide viewed better on the pc monitor than mine at so far

So next was point this at the VCR139A and results were not good at all :cry: well didn't cry that much ! bit of a whimper more like it .
with the best adjustments light level i was able to see the cross i made with some tape it just worked but poorly i would have no hope with a slide .
I knew it wasn't the monitor from the start as it displays video fine ...i suspected the CRT or PMT but i didn't know which now i have the old scope working next to the vcr139A i can see there's a colour difference ...i am not sure but i think the graticule is a filter i suspect the CRT colours are the same ..my hope is the problem might be fixed with a colour filter infront of the PMT but i will double check this scopes CRT phosphor colour data if any or i might have to look into this my self and pull the crt out from behind the graticule .
i will Just have a look again also at the PMT data if theres any thing showing the range i think the Other i have the RCA might have a wider colour range this one must be closer to the UV side .
BTW theres slight drift is due to my PMT camera is using its circuit duplicate of the monitors or visa versa both using its own crystal oscillator .
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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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Re: NBTV Television Analyst

Postby Steve Anderson » Wed Jun 03, 2020 4:36 pm

Most (but not all) PMTs are sensitive in the shorter wavelength region, blue and UV. By the time you get to the longer wavelength of green (the CRT phosphor) they are as good as totally deaf. Silicon is generally the other way around, better at red and IR. Cadmium sulfide (LDRs) has an approximate human eye response, but they're way too slow for this application. There really isn't an easy-to-suggest alternative...maybe a Plumbicon camera tube optomised for green? But that's a real hassle, don't even consider bothering...or (not easy) getting hold of a CRT with a blue phosphor....A P7 CRT maybe possible. It has a short blue flash followed by the very slow yellow/orange afterglow which the PMT will ignore...a suggestion, though not guaranteed. How short is that 'blue flash'? I really don't know, it still could be too long for what you are attempting to do here...

Steve A.
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Re: NBTV Television Analyst

Postby Harry Dalek » Wed Jun 03, 2020 8:00 pm

Steve Anderson wrote:Most (but not all) PMTs are sensitive in the shorter wavelength region, blue and UV.


Yes i recall Steve O's PMT colour camera so there must be PMTs at least of some use down to the red looking at the RCA chart this looks to be true .

The PMT i was using in the portable PMT flying spot camera video last post was a EMI 9524 with a S 11 bandwidth i am not sure if the S 11 bandwidth is the same for a EMI tube using a RCA Chart ..i will look into this ..

Looking at the data the RCA PMT spare i have below is a 2060 PMT and should be fine in the green light but is a S11 too...
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Colour of the old scope it does look like it is more a blue green than the standard green , well with that filter screen anyway .
Well the CRT in the scope is a 312p31B couldn't fine any data for it

By the time you get to the longer wavelength of green (the CRT phosphor) they are as good as totally deaf. Silicon is generally the other way around, better at red and IR. Cadmium sulfide (LDRs) has an approximate human eye response, but they're way too slow for this application. There really isn't an easy-to-suggest alternative...maybe a Plumbicon camera tube optomised for green?


The hardest problem is not knowing what the problem is but now understanding whats up i will just see if filter idea works with the current setup ....if it makes no difference i will try the second working PMT i have infact 2 others to test ....problem is the colour of the light so mixing colours might work as with what i think is happening with the scope screen .
An alternative of some sort well as a last resort i still have a few ideas before that ,i have got this far and the colour of light is not going to stop me now .

But that's a real hassle, don't even consider bothering...or (not easy) getting hold of a CRT with a blue phosphor....A P7 CRT maybe possible. It has a short blue flash followed by the very slow yellow/orange afterglow which the PMT will ignore...a suggestion, though not guaranteed. How short is that 'blue flash'? I really don't know, it still could be too long for what you are attempting to do here...

Steve A.


Tomorrow Steve i will look into filter before even changing any thing it might just be an easy fix ,if that works i will test it out on the PMTS wired up ...it doesn't really bother me that much as its just some thing else to learn ..i was confused till today with the results .
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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Re: NBTV Television Analyst

Postby Harry Dalek » Thu Jun 04, 2020 10:53 am

Well the filter idea or what i have didn't seem to do much ...the PMt was still deaf to the raster .
1 options now give up .....no !
2 test the other PMTS
3 just have a look what else i have handy
3 easy fix may be ...use the Trio scopes crt for the project swap another crt to replace it think its the same size and voltage wise to the 3bp1.
...i will just test the other PMTS next see how they go .


Edit ...well i have tested all the PMTs wired up and all are deaf to the VCR139A i also gave the 3bp1 a go deaf also ,i think it is going to come down to Using the old scopes CRT ,its the same size as the 3Bp1 so placement wise is more trickier .
One good thing about the scope crt face is flat unlike the older tubes...so good for the slide idea
i also tested it without the graticule infront as i noticed the graticule was a bluish filter it still worked and with a better focus using slides .
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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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Re: NBTV Television Analyst

Postby Harry Dalek » Fri Jun 05, 2020 8:23 pm

I took out the vcr139A which was the flying spot crt and swapped it with the 312P31B equivalent it seems 75AVB319 .............(https://www.eevblog.com/forum/repair/co ... le-repair/),least i know once i get a correct raster size and control it will work fine ,i have no data apart from the manual some where ,i think its closer to the higher voltage of the 3bp1 voltage from memory i will double check its old scope voltages see what it expects .

This scope uses the same circuit voltages at the Trio scope
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I wonder if the P3 in number relates to its phosphor time ?

So hooking it up to the lower voltage VCR139A its resulting raster is way to large ...the VCR139A also is a 4 volt heater the 312p31B crt is a 6.3v heater ... its not helping here either i just hooked it up to see how off it all is ,still the brightness and position controls work with it just size and brightness need work .

I will look into this tomorrow .
If any thing learning about the needs of flying spot CRT scanning and PMTs a bit more has been very useful nothing like practical experiments to learn .
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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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Re: NBTV Television Analyst

Postby Harry Dalek » Sun Jun 07, 2020 3:28 pm

Trying to even out the deflection on both the flying spot crt and monitor using the same deflection amplifiers is a problem here with this type of crt.
I was thinking i might be able to drop the large flying spot CRT raster Size with resistors to the deflection plates and it does sort of work but you do get distortion the raster bows towards the top and bottom of the raster lines so that went out the window ...i couldn't do to much with the high negative supply adjust raster size as the voltages for the crts are sort of similar resulting in what you get is what you get .

I can of cause adjust either CRT to correct raster size with the line ramp adjustments VR211 VR201 shown in Steves circuit below but not both at the same time for similar raster size.

Ok just leaves me to construct a second deflection amplifier just for the flying spot crt something i was not expecting to do as i did toss up this problem earlier in the build for the vcr139A and it did work fine with using the 3Bp1's ...pity the PMTs did not cooperate !

So what i plan to do is construct 2 more transistor Ramp Amplitude circuits as shown below end of circuit and feed this to the second deflection amplifiers then both CRTs will be independent for deflection adjustments but still be in sync ...i did account for extra circuit room earlier so not to much of a problem just have to build and wire in .
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3BP1 NBTV Initial 1-Model.gif
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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Re: NBTV Television Analyst

Postby Steve Anderson » Sun Jun 07, 2020 7:07 pm

Hmm, this comes as no surprise to me, two quite different CRTs requiring differing amounts of deflection drive, and whatever supply voltages might be needed for each. Nothing much to suggest here, it's a case of "ho hum" I guess...

Wish I could be more helpful...

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Re: NBTV Television Analyst

Postby Harry Dalek » Sun Jun 07, 2020 7:58 pm

Steve Anderson wrote:Hmm, this comes as no surprise to me, two quite different CRTs requiring differing amounts of deflection drive, and whatever supply voltages might be needed for each. Nothing much to suggest here, it's a case of "ho hum" I guess...

Wish I could be more helpful...

Steve A.


Pretty Much made decades apart ,i think the swapped CRT is from the early 80s the VCR139A 40s or 50s CRT .....design seemed to improved for the deflection needs after all those decades .
OH its Ok Steve answer was pretty much shown with a few tests ,On the positive side it does have the benefit of selecting the transparency size with out effecting the monitor display size and the CRT face is dead flat good for this job and i know it works with the PMTS
It also as made me try this like it or not a good learning exercise .
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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Re: NBTV Television Analyst

Postby Steve Anderson » Mon Jun 08, 2020 3:47 pm

I have a book which covers the evolution of the CRT from the very early days up until (almost) its demise....

"The Cathode-Ray Tube", Peter A. Keller, ISBN 0-9631559-0-3, 1991. It's worthwhile read , but may be hard to find. I got my copy direct from the author as he had a few spare copies. I think it's probably out of print now. I don't recall the cost, maybe US$50 including postage from the US. How I got in contact with the author I don't remember. He worked for Tektronix is the US, so I think you can assume it's authoritative.

An Amazon search or similar may be worthwhile...there are some download sites, but I wouldn't trust them....especially if they ask for your CC data...

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