Modeline 405 line Monitor

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The Build Starts !

Postby Harry Dalek » Sat May 28, 2022 5:09 pm

OK i can now turn off the pc and turn my mind to the monitor idea i have picked a tube i have handy not to big nice size for this ,its a 14SX3Y4 5.5inch black and white CRT having 12.6V 75mA heater with tests ok on a conductivity and voltage test .
Data for most CRTS like this are hard to come by but there are scraps of information gold
Filament voltage : 12V Filament current :75mA
Typical operation:
Final anode : 8KV
Vg2 : 100V there also have 300V version
Vg1 : -35V +/- 10V
some one in Poland who experimented with one mentioned the below
On the focus grid i remember the focus grid is connect to ground.. This are tetrode electron gun the final voltage 8KV will work well at lower voltage just the brightness will decrease.
Well we will see when i get around to it all a nice start .
Edit found some information on pin out of the tube apart from heater i have not looked into this so this is handy Dutch information found below
1 Grid
2 Cathode (K)
3 Heater
4 Heater
5 ??Grid?? (G1)
6 Grid (stuck on the same thing as 1) (G2)
7 ??Focus anode?? (7)
So a 12V filament. G2 must be adjustable between +100 and +300V. G1 is connected to ground where the cathode is somewhere around +35V on its cut-off. G4 is a question, probably the focus voltage is somewhere between 0 and +300V - you can make it adjustable or just hang it on a fixed voltage and see if it is sharp.
Also
14SX3Y4-002
Key Specifications/ Special Features:
Unipotential electrostatic focus Aluminized screen Electromagnetic deflection High resolution Fast starting cathode Fully-ground precision for high accuracy and excellent concentricity Size: 14cm (5.5 inches)
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Last edited by Harry Dalek on Tue Jun 07, 2022 9:25 pm, edited 6 times in total.
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Re: Modeline 405 line Monitor

Postby Harry Dalek » Sat Jun 04, 2022 8:24 pm

Working on the the deflection Board ,i have done a bit more than what is shown in the photo circuit board i am just finishing off the deflection amplifiers at the moment ,the sync separator seems to work at least down to 405 line 10khz 50hz so that's good
I suppose these days i could of used a amplifier chip for the deflection amplifier side but i am one for if it works why bother changing it and i have a junk box of parts every thing made so far is what i have in my parts collection .
So i think i can get it all working on 2 boards stacked the second would be power supply powering the circuits and CRT, having put together a few monitors now you learn from your mistakes and it gets easier ( i hope :shock: ) seeming that way on this build .
EHT 8Kv tossing up with using a flyback transformer or smaller bug catcher coil used a few times with no problems .
Edit deflection amplifier now shown
Attachments
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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: Modeline 405 line Monitor

Postby Harry Dalek » Thu Jun 09, 2022 5:25 pm

Moved onto the power supply this transformer was handy looks like a nice size to do the job and is giving 14v 0 14v and 7v 0 7v AC so i will work with that to supply the dc for the circuits and crt next.
I was thinking i could get it all on 2 boards but forgetting the EHT supply means if i ever case this it means positioning of the boards would be a problem with the short EHT cable positive to the last anode .
So i think it would be wise to put the flyback transformer on its own little board.
The Gif animation rather good explaining a magnetic deflected CRT and where i will be directing my power supply .
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Re: Modeline 405 line Monitor

Postby FlyMario » Fri Jun 10, 2022 1:43 am

I always look at these CRT demonstrations and can't understand why TV CRTs can be easily converted to an X, Y Scope without having to build some big deflection coil to put on the neck. TV already has deflection coils. What is the difference between the two Deflection coils? It seems that tv pretty much works the same way. It scans across and up and down.... x and y.
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Re: Modeline 405 line Monitor

Postby Harry Dalek » Fri Jun 10, 2022 8:29 am

FlyMario wrote:I always look at these CRT demonstrations and can't understand why TV CRTs can be easily converted to an X, Y Scope without having to build some big deflection coil to put on the neck. TV already has deflection coils. What is the difference between the two Deflection coils? It seems that tv pretty much works the same way. It scans across and up and down.... x and y.

Well they could but the problem is the yoke they are not good at working with different frequencies you will find the display shrinking and growing on the horizontal and vertical is designed for 50 or 60hz so a electrostatic tube is much better at this both plates can work and any frequency ,i have seen people try it as an audio scope bit limited .
Catch 22 with the project it would be easier with an electrostatic tube but the tube would have to be about 5 inch perhaps a newer scope tube could do it my old 40 50s tubes better for nbtv it would make the project much bigger to ,the magnetic tube is designed for 625 line so all this is no problem what i am doing just the yoke part will need make some tinkering if i go multi system
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Re: Modeline 405 line Monitor

Postby FlyMario » Fri Jun 10, 2022 9:07 am

Oh ok. Cool. It always bugged me. But I get it. The frequencies... makes sense. I remember when I was young in the '70s putting a battery on the deflection coils and moving the dot around.

But I have an XY scope and the neck on the tube is extremely long. Always wondered why the tube is so long.
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Re: Modeline 405 line Monitor

Postby Steve Anderson » Fri Jun 10, 2022 11:27 am

FlyMario wrote:But I have an XY scope and the neck on the tube is extremely long. Always wondered why the tube is so long.

Generally the longer CRTs for the same screen size will be electrostatic deflection rather than magnetic. For large screen sizes and/or large deflection angles the voltages required between the electrostatic deflection plates becomes excessive, even beyond what valves/tubes could handle. Magnetic deflection primarily requires current rather than voltage, any voltage seen across the coils is a result of winding resistance and self-inductance (it is a coil after all).

They both have their plusses and minuses. Magnetic deflection allows for greater deflection angles (shorter tubes) at the expense of linearity, whereas electrostatic is very linear due to the small deflection angles (ideal for oscilloscopes) but long tubes are the result. A compromise as ever.

Steve A.

In this video you can see the deflection plates and some of the reasons mentioned above as to why the tube is so long...

https://www.youtube.com/watch?v=NBeOMsdPuT8

This video from Tektronix is a 'refresher course' in the fundamentals of CRTs - it's also quite nostalgic in the subject matter and presentation style...

https://www.youtube.com/watch?v=jHGAnJjnNY0
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Re: Modeline 405 line Monitor

Postby Dave Moll » Fri Jun 10, 2022 6:30 pm

And, of course, with the larger screen size used in televisions, the CRTs needed to have shorter necks to avoid a set that extends several feet into the room - which is why some early sets had the tube mounted vertically to accomodate the length of the CRT, with a 45º mirror above. Just think of the shape of the average 'scope scaled up to a display 20"+.
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Re: Modeline 405 line Monitor

Postby Harry Dalek » Fri Jun 10, 2022 9:23 pm

Dave Moll wrote:And, of course, with the larger screen size used in televisions, the CRTs needed to have shorter necks to avoid a set that extends several feet into the room - which is why some early sets had the tube mounted vertically to accomodate the length of the CRT, with a 45º mirror above. Just think of the shape of the average 'scope scaled up to a display 20"+.


Yes Dave those 1930s CRTs were long i suppose they were electrostatic driven problem making the screen size larger .
Binnie Hale and Roger Treville mirror lid Television about 39 i think
119123770_10224677472263870_3095221712336862332_n.jpg

Funny enough talking of mirror lids had crossed my mind to pay tribute to 405 line and make a little mirror lid version my self as something different ,i do have a Box right size comes down to how well i can make this work .
On my site some members were telling me the Mirror lid tv's of the late 40s were normal size and didn't need to be mounted like that but the idea was kept to hide that crt away !
Yes Steve electrostatic and magnetic have their place depending what you need it to do ,best to use it for what it was made for dot sharpness and what it can do deflection wise with frequency reason its logical over 100 lines to use what i am . i do like magnetic as they are easier on the electron gun side it is a big toss up whats better .
Just about finished the low voltage supply testing ok so thats nearly out of the way

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Re: Modeline 405 line Monitor

Postby Harry Dalek » Sat Jun 11, 2022 6:54 pm

Well i finished off the low voltage supply today and started working on the HV supply board this afternoon ,needed to be about or just under 8Kv and up to 300V for focus , every thing i have used so far i have made before so fingers crossed every thing cooperates as in the past .
Just make it work i was told once i always thought that was good advice so i do a lot of thinking and make it work one way or another :wink: .
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Re: Modeline 405 line Monitor

Postby Harry Dalek » Mon Jun 13, 2022 5:35 pm

Checking out the CRT unfortunately i hadn't noticed a problem it had in its former life as a tv as its deflection must of died i am pretty sure thats a raster burn hole in the top right ,what i thought was dirt seems to be that .
The Tv it came from had no EHT or deflection working only the sound part was operational so suspect the deflection went before the EHT i suppose i will have to live with it :roll:
Bit of a downer as its been going rather well and nearly ready to fire it up The HV supply works and testing the vertical deflection so far on the yoke seems good too ,in and out of the power transistors shown below .
Then i got distracted ! i wanted to fix my resistor wheel which has been playing up for ages fed up i made my own version 1 ohm to 10 Meg ! :mrgreen:
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Re: Modeline 405 line Monitor

Postby Klaas Robers » Mon Jun 13, 2022 7:35 pm

That is strange........

In almost all cases a burn-in hole in the screen is at the center. When the deflection fails, the spot returns to the center of the screen (electrons running straight). And especially in a corner of the screen....... Then there was still a static horizontal and vertical deflection.

Very strange.
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Re: Modeline 405 line Monitor

Postby Steve Anderson » Mon Jun 13, 2022 8:10 pm

In 'normal' TVs the deflection is AC coupled, generally via some form of transformer or other, so a collapse of either, or both deflections can result in a burn either horizontally (vertical failure), vertically, unlikely as the EHT is usually derived from the horizontal deflection, or some other bizarre reason. (CRT cathode-grid short, internal to the CRT, it doesn't matter anymore, it's toast! ).

Whatever, it shows that when experimenting with CRTs of any type you must have a way to cut-off the beam when need be. Either manually (careful!) or automatic.

Steve A.
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Re: Modeline 405 line Monitor

Postby Harry Dalek » Mon Jun 13, 2022 8:55 pm

Klaas Robers wrote:That is strange........

In almost all cases a burn-in hole in the screen is at the center. When the deflection fails, the spot returns to the center of the screen (electrons running straight). And especially in a corner of the screen....... Then there was still a static horizontal and vertical deflection.

Very strange.


Yes but to me it sure look's like it put a tiny hole in the phospher as theres a little bit of dark smudge on the back of the glass face which i was thinking was just a bit of dirt on the screen but to my horror i saw what it really was ! which i would think are the electrons hitting it , but at that angle i see what you mean may be it happened very quick does not take much to do this i suppose if the deflection stops in an instant ?
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: Modeline 405 line Monitor

Postby Harry Dalek » Mon Jun 13, 2022 9:17 pm

Steve Anderson wrote:In 'normal' TVs the deflection is AC coupled, generally via some form of transformer or other, so a collapse of either, or both deflections can result in a burn either horizontally (vertical failure), vertically, unlikely as the EHT is usually derived from the horizontal deflection, or some other bizarre reason. (CRT cathode-grid short, internal to the CRT, it doesn't matter anymore, it's toast! ).

Whatever, it shows that when experimenting with CRTs of any type you must have a way to cut-off the beam when need be. Either manually (careful!) or automatic.

Steve A.


This was from a very cheap 20 year old tv cheap back then .
The Horizonal and vertical and EHT supply all dead in the scrapped tv the EHT transformer was fine as i used it for my supply and it works unless one of the windings i am not using failed i just needed the secondary for my use made my own primary .
I hope its not a internal crt problem ,i will keep on going with it for now and see what happens ....these things are getting rare these days when you see plasmas on the side of the road their time is long past .
I have another CRT bit larger i can swap it with if need be see how it gos .
Yes i hate how some old CRT tvs when turned off deflection gos and the dot looks like in time will burn a dot in the middle of the screen .
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