The Medium band Television Monitor

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The Medium band Television Monitor

Postby Harry Dalek » Sun Mar 26, 2023 6:56 pm

This build I will call the Medium band Television Monitor MBTV something i was looking into on the 405 line monitor MK 1 and Mk 2 but let down due to it being magnetically deflected ,did not work well below 405 line on this experimental monitor below .

DSCN8522.JPG
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Since i plan on using a discarded scope CRT i am going to have to put up with graticule markings on the display i expect similar results as here on 525 line shown on a scope .

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I have a 150btb31 CRT and another i am tossing up using donated from Troy here
150BT-B31.pdf
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I expect a viewing range as below what i can produce

405 10.12khz 50hz
240 12.82khz 53.44 hz
441 11.04khz 50hz
625 15.65khz 50hz
525 15.70khz 59.79hz
625 1500x580........15.60khz 49.92hz
107 2.674khz 25hz
819 20.52khz 25hz
120 2.677khz 25hz
Screen 00019.bmp
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The voltages the crt needs are nothing i have not worked with before but because this is a bit bigger to say the least than the 405 line monitor i will case it safety first .
I should have every thing laying around some where in my shed an old scope case handy should speed mounting it .
I recall testing the heater but best look again before i get underway with this tube .
Attachments
DSCN7008.JPG
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 Medium band Television Monitor

Postby Harry Dalek » Thu Mar 30, 2023 3:40 pm

Well had some time today to strip the old case of its insides and started to rewire the power in as i have tested my 290 0 290 6.3 v transformer it seems fine .
I will need another transformer for the low power supply.
Tossing up a Cockcroft–Walton multiplier as i used in The Beast monitor or Steve your multiplier in the Anderson Monitor for the 2KV ... i don't like the idea of using an inverter
I tested the Heater today to make sure its a working CRT and its fine .
The socket is numbered to the CRT pin side so that's good knowing what go's where once i number the sockets Board from the Back with the CRT plugged in that will make life easier :wink:
I suppose once the transformers are mounted i will work on the Multiplier and go step by step on the rest .
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 Medium band Television Monitor

Postby Harry Dalek » Fri Mar 31, 2023 4:44 pm

This one will be fun to make i really want to see what i can correct from the past go at this type of higher line system monitor .
Still a little bit boring but got to start some where , Ac power supply is wired up i still need to wire these to the Ac distribution board then i can work on the DC voltages .
The 70 i would think year old Transformer below still working fine very similar to what i used in the Anderson monitor power supply there's also a dual 12 volt transformer mounted under it for the low voltage supply .
DSCN7024.JPG


So today was mainly mount the transformers wire to up to mains safely and see where the power supply will go i always have to take into account have i forgotten some thing room wise for mounting the parts ,i have a lot of room in this for the boards but i think i will keep the CRT side the AC DC supply side of it .

I am not using the CRT that was in this case this one was donated to me By Troy it's the same size fits nice i will keep the original safe for another day no real reason for not using it but if any thing go's wrong i have a spare .

I am thinking of placing the HV DC multiplier in the case under the CRT neck the original Inverter was there has enough space for the job .
Attachments
DSCN7025.JPG
DSCN7030.JPG
DSCN7028.JPG
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 Medium band Television Monitor

Postby Steve Anderson » Mon Apr 03, 2023 12:16 pm

Harry Dalek wrote:I expect a viewing range as below what i can produce

405 10.12khz 50hz
240 12.82khz 53.44 hz
441 11.04khz 50hz
625 15.65khz 50hz
525 15.70khz 59.79hz
625 1500x580........15.60khz 49.92hz
107 2.674khz 25hz
819 20.52khz 25hz
120 2.677khz 25hz


I'm curious as to how you plan to provide a signal source for those various line and scan rates...two are easily generated or maybe you have a source already (525/60 & 625/50), the others need some thought...

Steve A.

Just noticed some of the lines/H freq/V freq figures don't seem to be correct. For example the last one in the list, 120 lines @ 25Hz vertical comes out to 3,000Hz, not 2,677Hz.

I have the data for UK, US, France/Belgium broadcast specifications for 405/25i (interlaced), 525/30i, 625/25i, 819/25i, the others I would need to find some reference data for...or make an intelligent(?) guess...

Also note that some standards were (very slightly) altered when colour was introduced. For example, the US 525 system was 525/60 (frame rate 30Hz) when monochrome, when colour was added the frame rate needed to be adjusted to approximately 29.97Hz.
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Re: The Medium band Television Monitor

Postby Harry Dalek » Mon Apr 03, 2023 6:32 pm

Steve Anderson wrote:
Hi Steve

I'm curious as to how you plan to provide a signal source for those various line and scan rates...two are easily generated or maybe you have a source already (525/60 & 625/50), the others need some thought...


I can do it with a certain type type of old gaming card that you can program for different line and frame rates with the (mode line program ) its what i used for the 405 line signal others not perfect but enough to be close enough for me for a range to useable outputs, it outputs the 3 VGA colours and combines them make a B/w signal via a little circuit with the line and frame rates when you have selected one .
A very cheap from PC screen or part a section of screen to a number of tv systems ,might not be perfect but for me it was 30 dollars for a second have gaming card and a little bit of wiring from the vga output ...a fair few people who collect 405 line tvs use the idea for a easy cheap way to display something on their old tv's .
You would more then likely be better than most making more correct use program and making the graphics card cooperate ,i have just been using what others have made , you really need a monitor to view any results unless your happy viewing the video waveform on just a scope .
When i get around to it i have to reload the program on my replacement PC the last one died on me ,BTW you need a dual display for this system one go's off when you you say select 405 line to use the video signal and the monitor screen can't use that to display any thing its a little confusing till you work out how all this works .
Attachments
Screen 00028.bmp
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Screen 00030.bmp
Screen 00030.bmp (545.4 KiB) Viewed 4626 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: The Medium band Television Monitor

Postby Harry Dalek » Mon Apr 03, 2023 7:10 pm

I am Still working on the voltage multiplier I have a 4 stage one of these it was giving me 2040 V with a 1 Meg resistor load till 2 of the caps died ,i was trying to take into account my the caps are rated 450v 22uf so used 2 of them per stage back to back and 2 1000v diodes so apart from that similar to the standard Cockcroft-Walton Voltage multiplier ,I think i should of placed 2 1 meg resistors across each capacitor even them out ,i think one died and fed the other well over what it was rated DC wise .
The transformer outputs 290v 0 290v AC so i was using to full 580v AC for the multiplier trying to cut down on the stages .
Have not had a capacitor go in a while had worse in the past some just explode or shoot off like a bullet these 2 just blew a little smoke :roll:
I should of stopped when i knew what was happening on start up second time around powering up reading on the meter it would go to full 2040 then start to drop back in voltage a dead giveaway a capacitor or more is going .
l
Attachments
circ371b (1).jpg
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Last edited by Harry Dalek on Tue Apr 04, 2023 3:50 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 Medium band Television Monitor

Postby Steve Anderson » Mon Apr 03, 2023 7:54 pm

I would need to look into that "Mode-Line" program myself, if it does what is says, well, it could be a valid source of signals. Where can I download it from?... I know you've mentioned it before...

As for the voltage multiplier, that could be done in fewer stages depending on the transformers you have and if they are required to provide other supplies as well. Most EHT supplies are a couple of mA at most usually....so multi-output HT/EHT power supplies are quite possible and simple. That includes deflection for electrostatic tubes. Electromagnetic CRTs are always a headache if multiple line/frame rates are needed...they are a headache whatever. If you plan to use an electrostatic CRT, stick with it.

Found the Modeline program here...

https://www.geocities.ws/podernixie/htp ... ne-en.html

...is that where you got it from?

Steve A.
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Re: The Medium band Television Monitor

Postby Steve Anderson » Tue Apr 04, 2023 1:37 pm

The issue with the Modeline program is that it seems to tie up your PC while outputting the TV waveform/picture - which is a bit of a pain - unless I've got it wrong. If you have a second PC that's OK, I only have the one, though it is dual-display - i.e. two 24" monitors on one PC. So, for example, I often have Excel on one screen and Autocad on the other, very useful when generating a parts list from a circuit diagram.

So in my mind I'm thinking of a non-PC hardware arrangement that can generate (maybe) 16 different selected modes. They could be a mixture of FSTV (525/625 etc.), NBTV and SSTV. SSTV may need an external subcarrier modulator in addition, but maybe not. It wouldn't be a scan-convertor, more of a SPG (Sync Pulse Generator) or a TSG (Test Signal Generator).

Steve A.

Though a down-convertor wouldn't be that hard, say 625 in, and all Harry's modes above, except 819 lines, could be output. 819 lines is possible but is the extra effort/expense worth it for just one 'standard'?
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Re: The Medium band Television Monitor

Postby Steve Anderson » Tue Apr 04, 2023 5:08 pm

It's true that certain precautions need to be taken with Cockcroft-Walton voltage multipliers, or any other multiplier. Here's my 'check-list' when I build one...which isn't that often...

1) All capacitors are new, ordered from the same supplier in one order (a good chance of a batch-match). They therefore should ideally all the same.
2) They all should have a voltage equalising resistor in parallel with each capacitor, but otherwise no load.
3) Once built, arrange some method of slowly raising the 240V supply, say 50V to start with, check voltages and polarities across each cap (and write down) are approximately equal, leave for an hour, check again.
4) Increase input voltage to say 100V, repeat above exercise...
5) Keep going in 50V increments until you've reached the full 240V input.
6) Shut down.

7) Repeat the above at least three times and compare results, allow some 'rest period' (hours) between tests so that the caps completely discharge.

'8) Lastly add the real load or a simulated one (a big suitable resistor or array).

9) By this stage the caps should have 'formed', they may have been stored for years, this is a gentle way of doing it.

10) Now if all the above looks good you should be able to apply the full mains voltage at switch-on without any problems....says he!

Steve A.
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Re: The Medium band Television Monitor

Postby Harry Dalek » Tue Apr 04, 2023 5:09 pm

Steve Anderson wrote:I would need to look into that "Mode-Line" program myself, if it does what is says, well, it could be a valid source of signals. Where can I download it from?... I know you've mentioned it before...


I see you found it ,i did link it on a past post .
Yes that's the latest one you have downloaded ...it's fussy on the gaming video cards that can be used but these days we are lucky as the original idea gaming dual display video card is very cheap now ,i am not sure if it works on newer video cards its one of those things if you have one give it a go and see .
There's a bit of a procedure to get it to work but as i said you need a dual display video card
MInes a ATI Radeon HD 2400 Pro
s-l1600 (7).jpg
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As for the voltage multiplier, that could be done in fewer stages depending on the transformers you have and if they are required to provide other supplies as well.


The old valve transformer i am using is a 290v 0 290v and 6.3 v i was planning on using it in a similar way to the Anderson monitor power supply ,i think if i used your HV negative supply copy of that circuit i might get around 1600 or 1700 perhaps tops yours is a voltage doubler from memory ? i wouldn't get higher voltages with adding more capacitor stages ? .
It's the main reason i am trying a Cockcroft–Walton multiplier first but it sure does make it be known if you have done some thing wrong !

Having played a round with them a bit i sort of dislike the magnetic deflection idea it was a bit of a pain to tame that deflection yoke last time around and can see why you like electrostatic is so much more .
Attachments
DSCN7035.JPG
DSCN7032.JPG
Last edited by Harry Dalek on Tue Apr 04, 2023 6:47 pm, edited 2 times 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 Medium band Television Monitor

Postby Harry Dalek » Tue Apr 04, 2023 5:16 pm

Steve Anderson wrote:It's true that certain precautions need to be taken with Cockcroft-Walton voltage multipliers, or any other multiplier. Here's my 'check-list' when I build one...which isn't that often...


Ok advice always taken in

1) All capacitors are new, ordered from the same supplier in one order (a good chance of a batch-match). They therefore should ideally all the same.


This i did all new same batch .

2) They all should have a voltage equalising resistor in parallel with each capacitor, but otherwise no load.


Here i stuffed up ! i will correct this

3) Once built, arrange some method of slowly raising the 240V supply, say 50V to start with, check voltages and polarities across each cap (and write down) are approximately equal, leave for an hour, check again.


This i can do with some AC supplies i have

4) Increase input voltage to say 100V, repeat above exercise...


Yep got a 100v AC

5) Keep going in 50V increments until you've reached the full 240V input.
6) Shut down.

7) Repeat the above at least three times and compare results, allow some 'rest period' (hours) between tests so that the caps completely discharge.

8) Lastly add the real load or a simulated one (a big suitable resistor or array).

9) By this stage the caps should have 'formed', they may have been stored for years, this is a gentle way of doing it.

10) Now if all the above looks good you should be able to apply the full mains voltage at switch-on without any problems....says he!


I will give it a go i went from a low voltage AC test to full with load i can see i should of been kinder to those capacitors ! 8)
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 Medium band Television Monitor

Postby Steve Anderson » Tue Apr 04, 2023 5:19 pm

No idea what's inside my PC, all I know there's two HDMI outputs on the back of it....I've never bothered to look inside...it works as I want, that's that! I have a similar attitude when it comes to cars. But motorcycles and aircraft I treat very differently...

I mentioned that the caps should be new, therefore unused, hence the gentle 'forming' process. Just because they are 'new' and unused to you, they may have been in storage for some years.

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Re: The Medium band Television Monitor

Postby Harry Dalek » Tue Apr 04, 2023 7:08 pm

Steve Anderson wrote:No idea what's inside my PC, all I know there's two HDMI outputs on the back of it....I've never bothered to look inside...it works as I want, that's that! I have a similar attitude when it comes to cars. But motorcycles and aircraft I treat very differently...


Well we are dealing with dual VGA output from the card for the mode line program to work so that's what we need .
Not sure these will pop up in your ebay area for for sale here very cheap ,i went for what i knew would work bonus its cheap now
https://www.ebay.com.au/sch/i.html?_fro ... o&_sacat=0

My son does know what's good and what's not these days in a PC ,i am just lost what's in top of the range these days more than likely i think same as you if it works i don't care .

I mentioned that the caps should be new, therefore unused, hence the gentle 'forming' process. Just because they are 'new' and unused to you, they may have been in storage for some years.

Steve A.

[/quote]

Yes mine are all new never used have a bag of 22uf 450V ones and and another with 10uf 450v just used the 22uf this time as in the photo on the page ,i started off with 12v AC to test it was giving 33v on load i was happy enough with that and gave it a full HV test well worked the first time second time things did not go well for the first 2 caps .
I will follow your test when i adjust the the circuit with the added resistors across the caps and replace the 2 bad ones
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 Medium band Television Monitor

Postby Steve Anderson » Wed Apr 05, 2023 11:47 am

I mentioned checking the voltage on each cap as you slowly increase the input voltage, but I also mentioned checking the polarity...I suggested that as you used the expression, "back-to-back", not 'in series'. Think of two people standing 'back-to-back', in my mind they would be facing in opposite directions. Here we want our series caps to 'face in the same direction'...not forgetting those voltage-equalising resistors across each cap as well...1 Meg is a reasonable value as the caps are of quite small capacity, but enough...but they can provide a serious 'jolt' to humans, so be careful...

The resistors also provide a discharge path when you turn off the power. How long should you wait before putting your hands in there? A very rough 'rule-of-thumb' is to multiply the capacitance in uF (in this case 22) by the resistance in Mohms (here, 1) which comes out to 22. Then multiply that by 5, = 110. The result is in seconds, 110 seconds is as good as two minutes, But the longer the better. Better still is to use a multimeter to measure if the residual voltage is safe.

I hope that is a clear explanation.

Steve A.

The above is based on the time-constant of a RC circuit, the example above has a time-constant of 22 seconds (22uF x 1M). At 22 seconds it should have 37% of the initial value. So if the cap was charged to 1000V, then disconnected from the source, after 22 seconds it will have 370V across it. Do that 5 times (the two minutes), the final voltage will be 0.37 x 0.37 x 0.37 x 0.37 x 0.37 times the initial voltage. Or approximately 0.7% of the starting voltage. In this example 1000V x 0.7% = 7V...quite safe...and that's without any other load except the 1M discharge/voltage equalising resistors. I would prefer to wait 2 minutes rather than have a 'zap' thank you!

There is a Wiki on 'Time Constant', but the maths is quite deep...the above simple version has been fine for me for over 40 years...
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Re: The Medium band Television Monitor

Postby Steve Anderson » Wed Apr 05, 2023 4:19 pm

Maybe your use of the full 580V AC might be an error. Can you sketch the final circuit you used?

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