The Tasmanian Devil VCR139....A for Andrew

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Re: The Tasmanian Devil VCR139....A for Andrew

Postby Steve Anderson » Sat Jun 10, 2017 9:50 pm

Andrew Davie wrote:...I'm afraid it's not very scarce; a DG7-32.

It's a nice easy to drive CRT, even easier than the VCR139A I would say...and physically smaller though the faceplate is the same size.

Attached are two screen-shots of a DG7-32, top at 48-lines, bottom at 72-lines. I converted them to greyscale to remove the green colour. I have posted these before in some other thread...

Steve A.
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Re: The Tasmanian Devil VCR139....A for Andrew

Postby Harry Dalek » Sat Jun 10, 2017 10:34 pm

Steve Anderson wrote:
Andrew Davie wrote:...I'm afraid it's not very scarce; a DG7-32.

It's a nice easy to drive CRT, even easier than the VCR139A I would say...and physically smaller though the faceplate is the same size.

Attached are two screen-shots of a DG7-32, top at 48-lines, bottom at 72-lines. I converted them to greyscale to remove the green colour. I have posted these before in some other thread...

Steve A.


Andrew it would always use them i hate the idea of them sitting in a box ..they should be made into a monitor or scope the DG7 32 sounds like its something like whats in my screen burnt old philips scope its a touch shorter to the VCR139A.

They may be past shots Steve but they showed me whats possible ! i got the bug now .
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: The Tasmanian Devil VCR139....A for Andrew

Postby Andrew Davie » Sat Jun 10, 2017 11:03 pm

Harry Dalek wrote:
Andrew it would always use them i hate the idea of them sitting in a box ..they should be made into a monitor or scope the DG7 32 sounds like its something like whats in my screen burnt old philips scope its a touch shorter to the VCR139A.


OK I'll get it to you. Worth it to me for at least two reasons;
1) great to actually watch your progress
2) I consider the forum is becoming a valuable online resource and "how to"

Maybe you can fix your scope...? Apparently this tube is often used for scopes.
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Re: The Tasmanian Devil VCR139....A for Andrew

Postby Harry Dalek » Sun Jun 11, 2017 10:24 am

Andrew Davie wrote:
Harry Dalek wrote:
Andrew it would always use them i hate the idea of them sitting in a box ..they should be made into a monitor or scope the DG7 32 sounds like its something like whats in my screen burnt old philips scope its a touch shorter to the VCR139A.


OK I'll get it to you. Worth it to me for at least two reasons;
1) great to actually watch your progress
2) I consider the forum is becoming a valuable online resource and "how to"

Maybe you can fix your scope...? Apparently this tube is often used for scopes.


OH Thanks Andrew are you sure i understand why i agree they should be used .
The forum is for me far superior to any magazine all a magazine can do is show whats been done and a long time delay between information the forum is Updating explaining so on time it takes some one to post something up very valuable ! i,d hate this to ever end !
The old philips scope is not very rare the CRT by the looks of it was used a fair bit over the years really over worked with a bit of screen burn right across the center i want to gut it now and leave the CRT and transformer keep case as is i hate the wiring in that 3d wiring in the air just above the inside case ,,,hard to work out and get at everything ..Not really good for a monitor due to the screen burn but would useful as a crt flying spot scanner don't have to use all the screen for that or it matters scanning a slide or home made testcard transparency you want a test card video signal more so for any line rate not possible unless you buy a systems converter ...i like old school technology so that fits in here the gap between 120 line and 405, it is a problem a no mansland because of a lack of video signal flying spot testcard maker would make this possible ...625 is easy as more than enough about for video signal .
The Next CRT would be systems above 120 to 405 .
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: The Tasmanian Devil VCR139....A for Andrew

Postby Harry Dalek » Sun Jun 11, 2017 4:23 pm

Today i fixed my 12 voltage positive supply problem i ended up using a lm317 no 7812's handy but i have 50 Lm317s ...worked fine the monitor now work fully from its power supply .
I also reversed the deflection plate connections for correct viewing and i have had a first go at 60 line ....Not great rolling on framing but got to live and learn .
I only had one file system at 60 line handy have to make some more ...This was using Doms software made a few years ago the sawtooth line frequency is showing up as 800 hz and the frame at 6hz ....vertical scanning its not locking so have a flickery roll at 6hz ....sounds like i am missing something like doubling the frame frequency perhaps so it locks at 12.5 hz as it did when i tried playing this file at 32 line 400 hz it locked fine when i was doing that .
I was not expecting a framing problem Doms software it says it 64 line NbTVA 64 it will play side ways for now but i will try Garys software to make some files up at dead on 60 line /


youtu.be/wy0ShHnoHMs
Attachments
IMG_2596.JPG
reversed the deflection plate connections for correct viewing...here still on 32 line
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IMG_2680.JPG
60 line
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NBTV australia 60line-48000-NBTVA64-p-II.wav
64 line NBTVA
(704.73 KiB) Downloaded 168 times
Last edited by Harry Dalek on Sun Jun 11, 2017 5:41 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: The Tasmanian Devil VCR139....A for Andrew

Postby Steve Anderson » Sun Jun 11, 2017 5:40 pm

Harry, the wave file you attached appears to have an 800Hz line rate and a 12.5Hz frame rate, i.e. 64 lines, twice the usual NBTVA standard. This means the frame circuits shouldn't require any changes, but the line timebase will need a change in a couple of components, maybe only one. I need to re-visit the circuits. You may wish to consider adding a switch to select 32/64 lines. Maybe a third position if you intend to go to an even higher resolution.

One thing to remember is now the bandwidth required has doubled from the usual 10kHz figure of 32-line NBTV to 20kHz. With 48kHz sampling as done here that's getting close to the limit if you wish to preserve resolution. In theory you also add another factor of two such that the vertical and horizontal resolutions are the same. A 40kHz bandwidth which can't be done with 48kHz sampling, 96kHz is required. Above 64-lines it gets even worse.

For the 72-line monitor I did some years ago I got around this by dropping the frame-rate to half the usual, 6.25Hz.

Steve A.
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Re: The Tasmanian Devil VCR139....A for Andrew

Postby Harry Dalek » Sun Jun 11, 2017 6:20 pm

Steve Anderson wrote:Harry, the wave file you attached appears to have an 800Hz line rate and a 12.5Hz frame rate, i.e. 64 lines, twice the usual NBTVA standard. This means the frame circuits shouldn't require any changes, but the line timebase will need a change in a couple of components, maybe only one. I need to re-visit the circuits. You may wish to consider adding a switch to select 32/64 lines. Maybe a third position if you intend to go to an even higher resolution.


i tried changing the timing capacitor 47nF to 33nf i stopped when i noticed the sawtooth is locking at 800hz any way but the frame sawtooth drops to 6 hz its still normal within range for 32 line video funny enough line still showing 400 hz and frame 12 hz .
I was thinking the 64 line video should have a 12.5 Hz framing rate but am still head scratch why its showing 6 hz on my frequency meter but saw looks like 6 with that 2 picture roll.

One thing to remember is now the bandwidth required has doubled from the usual 10kHz figure of 32-line NBTV to 20kHz. With 48kHz sampling as done here that's getting close to the limit if you wish to preserve resolution. In theory you also add another factor of two such that the vertical and horizontal resolutions are the same. A 40kHz bandwidth which can't be done with 48kHz sampling, 96kHz is required. Above 64-lines it gets even worse.

For the 72-line monitor I did some years ago I got around this by dropping the frame-rate to half the usual, 6.25Hz.

Steve A.
[/quote]

OH i see theres a dilemma is there a way for component switching with the bandwidth problem resolution which i suppose is due to our player the computer ...
On switching i did expect this but i had to see till now if its worth it once i saw what was needed to get to 60 line i was not sure if i just had to adjust the timing capacitor and or resistances also.
I have never tried 60 line electronic most of the time i am speeding up a motor with a pulley system for more speed to view 60 line and hoping nothing will fly off and do me in :wink: !
If it means 120 line i will have to do the flying spot scanning earlier so be it ..i have to look at my documents what was the standards here .

BTW what did you use for a video signal for 72 line Steve ?
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Re: The Tasmanian Devil VCR139....A for Andrew

Postby Steve Anderson » Sun Jun 11, 2017 6:45 pm

Harry Dalek wrote:BTW what did you use for a video signal for 60 line Steve ?

No, I've not done a 60-line or 64-line display before, that wave file is 64-line, not 60. I went to 72-lines for reasons I can't remember. 72-lines is about the limit for a 3" CRT as you can see in the photo I posted yesterday, the lines are starting to overlap. It's simply down to the focused spot size. Unless you go up to a 5" CRT you're not going to see any improvement at 120-lines. I would say 120-lines on a fairly modern 5" CRT is probably the limit.

You can put 405 lines or more on a 5" CRT but you won't see much improvement in the picture resolution. More useful would be increasing the frame-rate to reduce/eliminate flicker.

The DG7-32 saw a lot of use in simpler oscilloscopes in the 60s era, especially in educational applications. It also was used in a Marantz FM-tuner to display stereo separation, a bit of a gimmick really. As shown below it possibly had a different phosphor to the standard version.

Steve A.
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Re: The Tasmanian Devil VCR139....A for Andrew

Postby Harry Dalek » Sun Jun 11, 2017 9:42 pm

Sorry Steve i had 60 line on the brain i meant to say 72 what did you use as a video signal ?

No, I've not done a 60-line or 64-line display before,


OH i am surprised we are in the same boat here on the non mechanical side of it here !

that wave file is 64-line, not 60.


Yes checking Doms software i see it says 64 NBTVA standard ? frame rate you said 12.5 vertical scanning ,i see Garys software does 60 line 750 hz 12.5hz but horizontal scanning .

I went to 72-lines for reasons I can't remember. 72-lines is about the limit for a 3" CRT as you can see in the photo I posted yesterday, the lines are starting to overlap. It's simply down to the focused spot size. Unless you go up to a 5" CRT you're not going to see any improvement at 120-lines. I would say 120-lines on a fairly modern 5" CRT is probably the limit.


Thats oK i understand problem here Steve its a pity its a problem not fixable unless you use a larger CRT /
i am interested in the learning exercise and more just having the display to show something at that line rate it is a start for me bit like the many 625 line electrostatic tv projects out there you have a display i found this below on 240 line on a scope ..
original ....https://www.vintage-radio.net/forum/sho ... php?t=9229
Perhaps not perfect but results like this link below are fine if mine could also do the same.... this tube is older i think than mine and smaller
http://members.iinet.net.au/~cool386/902tv/902tv.html

You can put 405 lines or more on a 5" CRT but you won't see much improvement in the picture resolution. More useful would be increasing the frame-rate to reduce/eliminate flicker.


I noticed on Garys 120 line software hes is at 25hz i have no idea had he got it to fit may as you said the sampling rate but beyond me /

I will just have a look what was about above 60 ...standards

The DG7-32 saw a lot of use in simpler oscilloscopes in the 60s era, especially in educational applications. It also was used in a Marantz FM-tuner to display stereo separation, a bit of a gimmick really. As shown below it possibly had a different phosphor to the standard version.

Steve A.[/quote]
I tried Garys 60 line similar results thats my daughter a few years older these days the dreaded 13 !

youtu.be/maRspw61xEs
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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: The Tasmanian Devil VCR139....A for Andrew

Postby Harry Dalek » Tue Jun 13, 2017 5:15 pm

The monitor works fine at 32 line so circuit wise i will move onto 60 line .
i will work next on getting 60 line to work correctly adjusting the circuits postings so it will be less confusing if i add 60 line subTopic to The Devil .
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
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