NBTV Scope Evolution

Forum for discussion of electronic television. Generally, stuff to do with CRTs and not using mechanical displays.

NBTV Scope Evolution

Postby Harry Dalek » Sun Jun 07, 2015 12:28 pm

About 10 years ago i made a nbtv monitor scope with my trio scope ,one of those things where i never drew a schematic been thinking how i did this back then in an afternoon and it worked ,it was as i recall pretty simple i used a TTL monostable for the sync dectection could of been a 74121 or 123 for the horizontal sync had 2 555 oscillators the 400hz line sync synced the line 555 , frame used a 555 was free running and one transistor for the video ...here i recall i used a transformer backwards with one lead of the secondary conected to the collector other to the power supply this isolated the circuit from the HV of the CRT and gave enough voltage to change the intensity ....Thinking about the transformer i am vague about what i used it was either a mains transformer would have to low a bandwidth to work thinking about it now ,it was more than likly a Audio transformer would have enough bandwidth to produce a picture ...
Results were good did have picture roll as the framing was manual control..but it was pretty simple .

There are a few scope circuits out there but its more fun to try and make your own than copy all the time .....heres a different idea i have been thinking about ...

I know i can use a 4060 to output both the line and frame frequencies but i would need to sync this clock to the incoming line frequency if possible easier to use a crystal but i suppose a R/C clock would be possible to depends if i can find the right crystal.... have it i hope in with the rest of my crystals ..so thinking about this in the drawing using a bistable so the line controls the 4060 via reset ,not sure if this would work ? ...i more than likly need a sync seperator before the 555 bistable but this is the basic first idea at the moment for syncing and getting both line and frame frequencies for the ramp generators they could be 555s as well.

Could sync another way via the 555 ramp generators via pin 5 that might work too ...

The video side i need to look into what scope i have does what before working any thing out here .
Attachments
scope idea 1.JPG
if i can get the crystal clock to sync with the video
scope idea 1.JPG (121.44 KiB) Viewed 12284 times
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Re: NBTV Scope Evolution

Postby Harry Dalek » Sun Jun 07, 2015 6:06 pm

I should really bread board this but i know most of it works and i enjoy freestyling !

Startng i was thinking may as well see if i can get the clock going ,i went for a R/C 4060 oscillator my crystal is still in another circuit which i would rather keep there for now ... :wink:

Results look ok i have the 400 hz line 12 hz frame rate..

The schematic is from a past project so ignor the to 4528

I knew this part would work as i made one before, funny enough i was only 2 hz off on the trimmer adjustment when i tested it .
The switch is for the chips reset pin 12 switched to ground for now and there to see if i can be of use in syncing as i mentioned before i will try it one way or another ..just hedging my bets.
Attachments
circuit.JPG
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circuit2.JPG
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400.JPG
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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 Scope Evolution

Postby Harry Dalek » Mon Jun 08, 2015 6:27 pm

Added the sawtooth circuits today had to work out the correct charging capacitors for both generators cheated a little switching a few in and out of the circuit ,the ones in the schematic worked the best ...also putting in the trimmers were well worth it with out knowing the correct resistors .

Also the capacitor value in the 4060 clock gave me 400hz out of pin 13 and 12hz out of pin 3 .

I will work out a sync decector and syncing this next .
Attachments
saw tooth tv.JPG
saw tooth tv.JPG (101 KiB) Viewed 12266 times
sawtooth400.JPG
sawtooth400.JPG (152.75 KiB) Viewed 12266 times
sawtooth12.JPG
sawtooth12.JPG (161.14 KiB) Viewed 12266 times
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 Scope Evolution

Postby Harry Dalek » Fri Jun 12, 2015 3:22 pm

Worked out a sync seperator using part of the the club circuit but using an AN1358 , i was going to use the Mc1458 as in the circuit below but this ic worked much better ,nice clean pulse .

i have not used the luxeon or led modulating ic and such part of the circuit just the first 2 opamps that is used for the sync.

Next i will add a bistable circuit feed the clock and sync from the sync seperator to it ...then feed the out put to the line ramp generator .e

Update on this the bistable circuit addition worked ..I will look into the video signal now ,i suppose i could just use the circuit posted here as is using the 3rd opamp and trany same sort idea .

I looked into the other frequency out puts from the 4060 clock and i noticed i am getting 800 and 1600 from 2 of the other outputs ,would not be to hard to put a switch in for this 60 120 line ,i think i would also have to switch the caps in the line sawtooth also but some thing to think about later.
Attachments
an6562-datasheet.pdf
The An1358 works
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IMG_0963.JPG
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Picture 32005.jpg
Picture 32005.jpg (281.11 KiB) Viewed 12239 times
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 Scope Evolution

Postby Harry Dalek » Wed Jun 17, 2015 12:00 am

Looking into the spot modulation came across some information posting here for me and others and replacing the higher line rates in the first image for NBTV its same idea .

Image 2 is interesting showing the various ways and effects of hooking up a scope television .

I am not sure as in the way image 3 and 4 have been modulated it wasn't explained, to me it looks like image 3 is spot wobble ? and 4 line wobble literally , looking into it there seems to be a few more ways to do it than the 2 which i suppose is up to what effect you want .

Some thing i didn't know the external trigger, sometimes labeled "Ext. Sync.," "Ext. Input," or "Z-Axis Input are the same ?
Attachments
Device Layout (2).jpg
Device Layout (2).jpg (93.1 KiB) Viewed 12209 times
1060_xyz_scope_sigs_1.jpg
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97_image_1.jpg
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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 Scope Evolution

Postby AncientBrit » Wed Jun 17, 2015 5:55 pm

Hi Harry,

Ext.Sync is an alternative to using the Y signal to trigger the X axis timebase and allows the timebase to hard lock to say 525 or 625 mixed syncs.

Z axis or Z mod is a feed to brightness modulate the CRT tube and can go either to grid or cathode.
Can be used to brightness modulate a raster.
Normally the Z mod is fed internally from the timebase and used to blank the flyback portion of the X axis scan

So they are separate feeds.

Cheers,

Graham
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Re: NBTV Scope Evolution

Postby Harry Dalek » Thu Jun 18, 2015 6:04 pm

AncientBrit wrote:Hi Harry,

Ext.Sync is an alternative to using the Y signal to trigger the X axis timebase and allows the timebase to hard lock to say 525 or 625 mixed syncs.

Z axis or Z mod is a feed to brightness modulate the CRT tube and can go either to grid or cathode.
Can be used to brightness modulate a raster.
Normally the Z mod is fed internally from the timebase and used to blank the flyback portion of the X axis scan

So they are separate feeds.

Cheers,

Graham


OH yes Graham my little trio Scope has this i recall using this for a scope tv before ,think i am getting confused reading this screen grab from this web site .
https://mbhs.edu/~jeglick/TV.html.

EDIT

Just seeing what Steve has said ,i can see the above web site is a bit of a mix truth and mistakes i will leave the link up in case any one else comes across it like me .
Last edited by Harry Dalek on Thu Jun 18, 2015 7:53 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 Scope Evolution

Postby Steve Anderson » Thu Jun 18, 2015 7:33 pm

Clearly this guy didn't do much research into the subject and fumbled around until he got what he appears to have wanted. I suggest you delete that text.

'External Trigger' or 'External Sync' is precisely what it says it is, an external waveform triggers the internal timebase, without that trigger you have no trace unless the 'scope timebase is in 'Auto + External' mode where the timebase free-runs until it detects a external trigger signal.

The Z input is a signal applied either to the grid circuit of the CRT (more positive - less negative) and makes the trace brighter, the converse if applied to the cathode. No different to CRT based TVs.

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Re: NBTV Scope Evolution

Postby Harry Dalek » Thu Jun 18, 2015 8:42 pm

Steve Anderson wrote:Clearly this guy didn't do much research into the subject and fumbled around until he got what he appears to have wanted. I suggest you delete that text.


It had me confused which is easy to do :? its gone now .... i left the link up as to why i got confused .

'External Trigger' or 'External Sync' is precisely what it says it is, an external waveform triggers the internal timebase, without that trigger you have no trace unless the 'scope timebase is in 'Auto + External' mode where the timebase free-runs until it detects a external trigger signal.


Well he must of had a Z connection and just thought the others were the same thing assuming can get you into trouble i can see.

The Z input is a signal applied either to the grid circuit of the CRT (more positive - less negative) and makes the trace brighter, the converse if applied to the cathode. No different to CRT based TVs.

Steve A.
[/quote]

The scope you helped me on fixing a little while ago ,that has 2 bnc plugs back of the scope ch1 output ... blanking but no Z connection the old 60s valve scope i have does but not sure what voltage it would take to vary that one ...

I just had a look at trying a voltage to vary the spots luminance with the blanking connection ,just tried it with a power supply up to 30 volts ,there seems to be varying the intensity doing the same as a Z connection this would be connected to the cathode if its blanking i think.
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Re: NBTV Scope Evolution

Postby Steve Anderson » Fri Jun 19, 2015 5:36 pm

The scope with the CH1 output allows the use of the CH1 input as a pre-amplifier for some other external device. It could be a spectrum analyser, a chart recorder or a multitude of other things. It is quite a useful feature but few 'scopes have it.

Z-input and blanking will effectively be the same thing, if you're using an external timebase (which could be the NBTV frame sweep, i.e. right-to-left) you'll also need to apply external blanking during the frame retrace time. This would need to be added to the actual video information...but that's no big deal.

The amount of volts required and the polarity for the Z-input or blanking will vary from one instrument to the other. It depends on the CRT used and the applied CRT supply voltages. If you can get/download a manual it should be mentioned in the specifications section.

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Re: NBTV Scope Evolution

Postby Harry Dalek » Fri Jun 19, 2015 9:52 pm

Thanks Steve Good to hear it is about the same thing ,have to look at the valve scope to see if i can get any result out of its z conection also .

BTW i noticed what ever CRT this mid 60s scope uses its not a p1 it has a lot of scanning lag next time i open it up i will have look ....i know it has a metal shroud around it where the tubes number is more than likly obscured.

See if i can track down any manual.
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Re: NBTV Scope Evolution

Postby Harry Dalek » Sat Jun 20, 2015 8:13 pm

Looking at 2 of my scopes today, this is what i mean about my 60s scope having lag something other than a p1.

I think the reason this oscilloscope has such a slow phosphor is for a scope it can do a very slow trace up to seconds to trace across the screen so i suppose having this it can display a slow waveform like a chart recorder .

I think its a p4 but counting what i can see on the screen seems about this end of trace .

P4, GE ZnO:Zn Green 505 nm – 1–10µs VFD sole phosphor in vacuum fluorescent displays.
P7 (Zn,Cd)S:Cu Blue with Yellow persistence 558,440 nm – Long CRT Radar PPI, old EKG monitors

I also fixed the bnc plugs on the back of my Tel-Instrument oscilloscope for the blanking and ch1 input the back of the scope had got a nasty knock and the connections where damaged no useable with a plug any how .

Also gave me a chance to flaten the back panel knock ...

I have made changes to my circuit ,made the sawtooth generater free running, it will now also sync to the videos sync ,it was much simpler to also just use
the sync pulse and feed it direct via a cap to pin 2 of the sawtooth circuit ,so the bistable with added led is just a nice 400 hz sync indicator ,

Got side tracked today on the Tel-Instrument connections repair .
Attachments
MVI_0971_mpeg4.gif
bwd scope working
MVI_0971_mpeg4.gif (10.03 MiB) Viewed 12148 times
IMG_0577.JPG
bwd scope
IMG_0577.JPG (115.84 KiB) Viewed 12148 times
anigif.gif
anigif.gif (251.38 KiB) Viewed 12147 times
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Re: NBTV Scope Evolution

Postby M3DVQ » Mon Jun 22, 2015 9:43 am

What I did on my scope driver is rather than have the counter triggering a pair of sawtooth generators which seemed awfully fiddly to make linear to this youngster from the digital age ;) I constructed one long (I think 12 bits) synchronous counter clocked from the appropriate bit of the 4060. I connected the outputs up to a pair of DAC ladders, 5 bits for X and the rest for Y. I seem to recall I did some sort of synchronous load rather than a complete reset since I reset on the missing pulse so am always a fraction late. I believe the crystal was a 3.2768 MHz one since that divides down to the 12.5 Hz.

I assume that if you do missing sync detection for frame sync on yours you will get the video drawn slightly shifted up the first line unless you find a way to build in regeneration of the sync pulse from your counter if it doesn't get reset. I just have a small black region at the corner the length of time it takes the detector to realise the sync was missing.

I think I built a spot killer into the Z driver by just triggering another monostable off the sync separator, unfortunately since on my scope higher voltage = dimmer spot there's no protection if the power gets interrupted. That would certainly be a benefit of using the scope's own timebase circuits and feeding it an external trigger pulse but that's only much use for horizontally scanned systems. :(

Alas my schematics are all in pencil on tatty bits of paper somewhere folded up in the workshop somewhere. I've never been much good at writing up my experiments properly :?
The sweep generation's not very 'analogue' so not to everyone's taste but people seemed to like the image quality at the convention :)
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Re: NBTV Scope Evolution

Postby Harry Dalek » Mon Jun 22, 2015 8:07 pm

M3DVQ wrote:What I did on my scope driver is rather than have the counter triggering a pair of sawtooth generators which seemed awfully fiddly to make linear to this youngster from the digital age ;) I constructed one long (I think 12 bits) synchronous counter clocked from the appropriate bit of the 4060. I connected the outputs up to a pair of DAC ladders, 5 bits for X and the rest for Y. I seem to recall I did some sort of synchronous load rather than a complete reset since I reset on the missing pulse so am always a fraction late. I believe the crystal was a 3.2768 MHz one since that divides down to the 12.5 Hz.


Was yours this breadboard posted here ....thats some amazing breadboard work ! I get a bit worried with digital projects as most of the time you can't see the results till the end if its complex .

I wish i could enjoy breadboarding but i hate doing it my self :roll: very logical and best way to see if an idea works ,may be its the rats nest wiring mine ends up looking like ,then having to remake it all again solder pcb version.

I don't have a spare crystal handy ,i do have that one but its soldered in another project so a RC oscillator will have to do for this idea for testing ,doing it again i don't think i would of even bothered with the 4060 but its there so i will make use of it .

This project could be more complex or even more simple i recall its been done with just one 555 timer ,just free styling an idea seeing how it gos when testing changing bits and such as i go ,suppose its how you learn .

I assume that if you do missing sync detection for frame sync on yours you will get the video drawn slightly shifted up the first line unless you find a way to build in regeneration of the sync pulse from your counter if it doesn't get reset. I just have a small black region at the corner the length of time it takes the detector to realise the sync was missing.


I am just using line syncing at the moment the frame i was thinking Yes a monostable as the missing pulse dectector .

I think I built a spot killer into the Z driver by just triggering another monostable off the sync separator, unfortunately since on my scope higher voltage = dimmer spot there's no protection if the power gets interrupted. That would certainly be a benefit of using the scope's own timebase circuits and feeding it an external trigger pulse but that's only much use for horizontally scanned systems. :(


Did you end up building it other than bread board version ? looked a very interesting design well beyond my diglital skills! So yours had no raster if you had no sync .?

Alas my schematics are all in pencil on tatty bits of paper somewhere folded up in the workshop somewhere. I've never been much good at writing up my experiments properly :?
The sweep generation's not very 'analogue' so not to everyone's taste but people seemed to like the image quality at the convention :)



I am a pen and paper schematic drawer my self i use a sketchbook so i can go back to it ,i take a photo of the schematic that helps as well .

Well it worked great , you can't ask for more than that i think you would have a lot more interest if you ever track down the circuits .

I have been side tracked looking at my scopes for the last few days one i also have the old 80s trio has a z connection 25v to blank the screen ,the other scope i have i can adjust the brighteness while adjusting with a DC supply to its Z connection the valve scope i have had no luck so far ,Reading the manual on 25 v Ac to blank it and looking at C121 on this one i don't think a DC test will not work ? i will try an Ac supply see what happens the valve scope might be similar .

I tried a 30 volt ac on both the valve and trio scopes here was no effect at all on the trios z connection ,The valve scope more of a slight effect on the spot shape if any thing . may be just a bad capacitor ...doesn't seem to be much to go wrong .
Attachments
harlequin.jpg
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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 Scope Evolution

Postby M3DVQ » Tue Jun 23, 2015 5:49 am

Heh, that breadboard isn't mine but I have seen it "in the flesh" at the Vintage Computing Festival they held at Bletchley Park. That's a cycle accurate* clone of the 48k Sinclair ZX Spectrum built in discrete logic by a brainy chap called Chris Smith. My breadboarding efforts often start off with various ideals like using particular colours of wire for particular types of signal etc, but then as things get unplugged and rewired to fault find it gradually moves towards maximum entropy ;)

*actually there's a small liberty taken to allow the use of an SRAM instead of DRAMs but iirc it does work fine with DRAM.
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