NBTV Television Analyst

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Re: NBTV Television Analyst

Postby Harry Dalek » Sat Apr 04, 2020 3:27 pm

The voltage doubling idea has worked out ,i changed this circuit for the 800 volts .
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Forgot to add the positive negative on the end cap chain positive to ground and or towards ground direction negative out top
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The output voltage is giving a touch more than what 4 caps at 450 volts are rated at might have to add another seems fine but better add another .
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Its seemed i needed 8 1000 volt diodes here just really add 2 caps and changed the diodes around a bit i was using for the bridge rectifier i tried a few hours ago so have the PMT and CRT negative voltages are some thing i can work with ,1600 for the CRTs is doable .

I found the 2 caps on the AC transformer hold there charge on switching off ..would they work and discharge with some resistors across them ?
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Re: NBTV Television Analyst

Postby Klaas Robers » Sat Apr 04, 2020 8:07 pm

Four capacitors of 450 V each in series is 1800 V. Then is 2200 V a little bit too high.! So add at least two extra capacitors in the right chain, and one extra in the top horizontal chain.....

And yes, place resistors of 1M in parallel to the capacitors connected to the AC transformer (horizontal chain).
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Re: NBTV Television Analyst

Postby Harry Dalek » Sat Apr 04, 2020 8:17 pm

Klaas Robers wrote:Four capacitors of 450 V each in series is 1800 V. Then is 2100 V a little bit too high.! So add at least two extra capacitors in the right chain.....

And yes, place two extra resistors of 1M in parallel to the two capacitors connected to the AC transformer.



Yes i agree pushing my luck with the capacitors ,i just didn't know if it would double the voltage and it sure did ! 2 extra caps might be a good thing as it will split down the voltage more would rather it just below 1600 ... then i can tap the voltages that work the best .

I will add the resistors mentioned also tomorrow !
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Re: NBTV Television Analyst

Postby Klaas Robers » Sat Apr 04, 2020 8:32 pm

Harry, you can't just tap the voltages that you need from the taps of the capacitor chain. As soon as they "draw current" they will drop in voltage, as the DC-current has to come from the high ohmic 1M resistors. You might use resistors of a lower value, e.g. 100k, but then at the same time you might need to make the capacitance of the electrolytic capacitors higher.
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Re: NBTV Television Analyst

Postby Harry Dalek » Sat Apr 04, 2020 9:59 pm

Klaas Robers wrote:Harry, you can't just tap the voltages that you need from the taps of the capacitor chain. As soon as they "draw current" they will drop in voltage, as the DC-current has to come from the high ohmic 1M resistors. You might use resistors of a lower value, e.g. 100k, but then at the same time you might need to make the capacitance of the electrolytic capacitors higher.


If its not to to bad that could be a good thing ! if the 1600 drops to 1400 say with the load ? i would be very happy ..

The Binocular project the voltage dropped from 1400v to 1200v under load got to work both crts fine on that so i have a 1000 volts to play with i think it should be in range some where from the power supply ..

Thanks for telling me i will know whats going on ,i know the 3Bp1 runs happy at 1400 v it would run fine higher to but sparking becomes a problem in the circuits if i construct parts to close or not remove matrix copper between connections something i would have to do 1600v and higher .
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Re: NBTV Television Analyst

Postby Klaas Robers » Sun Apr 05, 2020 4:46 am

But be aware that the voltage per capacitor should not go higher than the rated 450 volts. You can do clever things with resistors slightly lower than 1M to compensate for the voltage drop. I don't like it, but it is a possibility.

Good luck!
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Re: NBTV Television Analyst

Postby Harry Dalek » Sun Apr 05, 2020 8:23 am

Klaas Robers wrote:But be aware that the voltage per capacitor should not go higher than the rated 450 volts. You can do clever things with resistors slightly lower than 1M to compensate for the voltage drop. I don't like it, but it is a possibility.

Good luck!



Yes for Sure i will add another 2 capacitors to day distribute the voltage safely .

I sort of used the idea before the top voltage out of the last multiplier on the binocular it was 1600v top voltage out i used the next voltage down 1400v with load dropped to 1200v steady any case its workable ,i am happy the voltage doubling circuit is behaving even as is but i will make it safer now, and
and move on to the dual 12 volt supply .

The Heater windings i have a 7.3 out of the transformer i plan to use that just for the CRTs.

The main thing with all this to make every thing as safe as possible nothing heating up (apart from the crt heaters :wink: )nothing sparking everything working within range and safe to work on .
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Re: NBTV Television Analyst

Postby Steve Anderson » Sun Apr 05, 2020 2:33 pm

You may need a low-value dropper resistor for each CRT heater - though that 7.3V will drop a bit with the CRT heaters connected, best to keep the heater voltage within 10% of the nominal 6.3V (I presume), better would be 5% which is what I try and aim for.

Don't forget your meter, especially on low-volts AC ranges, it can have several percent of error...and the calibration 'goes off' with age and often the battery voltage.

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Re: NBTV Television Analyst

Postby Harry Dalek » Sun Apr 05, 2020 3:24 pm

Steve Anderson wrote:You may need a low-value dropper resistor for each CRT heater - though that 7.3V will drop a bit with the CRT heaters connected, best to keep the heater voltage within 10% of the nominal 6.3V (I presume), better would be 5% which is what I try and aim for.

Don't forget your meter, especially on low-volts AC ranges, it can have several percent of error...and the calibration 'goes off' with age and often the battery voltage.

Steve A.



OK Steve i will look into that i added a resistor last time but i will aim for a close 6.3 v supply ..i will be double tripple check that !

I was looking into the Anode supply 400 volts i tried a tiny mains transformer in reverse on the 7.3 volt so the 6 volt winding on that it gave 200 volts and 100 on 12 volts didn't seem to warm up so might be an easy solution to the anode supply ...a voltage doubling circuit seeing it also has to supply the deflection amplifiers also i might find some thing a bit bigger...r have another think about taping it off the 800 but that would be a bit more tricky ...
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Re: NBTV Television Analyst

Postby Steve Anderson » Sun Apr 05, 2020 4:22 pm

Meter Calibration or testing isn't that easy. Where can you get an accurate source of both AC and DC current and voltage? Same goes for other equipment, e.g. Oscilloscopes. The test and calibration equipment needed is often hideously expensive and needs re-calibration itself every so often.

Some years ago I acquired a 5V regulator (from where I don't recall) that is within 0.1% of 5V. It looks for all the world like a standard 78L05 but I guess selected for the tolerance. Of course that's when new, what the drift may be over time (and temperature) I don't know. Add a 1k 0.1% resistor and you have a reasonably accurate 5mA DC current...though don't forget the meter will have some internal resistance.

That's all fine and well for DC low-voltage and current, but what about higher figures? Then AC? It's a specialised industry, one I admit I know little about.

One of the easiest is time or its inverse, frequency. Even the cheapest crystal is far better than 0.1%. Get a GPS receiver and the 1 pulse-per-second output[1] is often within 10ns (nano-seconds) of UTC time, 0.000001% That figure gets better over a longer period of time. Today you can have an atomic-standard time reference in your home for just a few dollars. (I guess the Europa (Europe) and Glonass (Russia) systems are similar or better in accuracy...or the Chinese version, BeiDou).

But that doesn't fix our multimeter or 'scope issues.

Steve A.

[1] Most commercially made GPS receivers don't have a 1PPS (one-pulse-per-second) output. If interested I can direct you to a kit (just the PCB, the PCB components and antenna) that's under US$30 that does...as well as the NMEA data output you may want to use. I use two of these, and they work. Not from me, a guy I've known online for some years. If you're interested send me a PM for the URL.
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Re: NBTV Television Analyst

Postby Harry Dalek » Sun Apr 05, 2020 4:53 pm

Steve Anderson wrote:Meter Calibration or testing isn't that easy. Where can you get an accurate source of both AC and DC current and voltage? Same goes for other equipment, e.g. Oscilloscopes. The test and calibration equipment needed is often hideously expensive and needs re-calibration itself every so often.


Thats true i would have no hope ..On things like crystal frequencies meters if it shows what is expected i would trust it any thing else frequency wise i would have to compare it to a known accurate frequency if its showing true with that crystal frequency say divided down its more than likely going to show what a less accurate frequency oscillator is producing ....ON voltages low voltages DC is a little easier with know regulators expected output voltages ,if the meter is showing whats expected or out round about a volt i would be happy ..

Reason at first on the high voltages i was double triple checking with other meters as i really had to know if what was there is what my meter was showing (my faulty meter was showing 350 volts ! that can go in the bin now ) then i just used one but as you say how accurate to the volt that is ? only work in a range i suppose .

Some years ago I acquired a 5V regulator (from where I don't recall) that is within 0.1% of 5V. It looks for all the world like a standard 78L05 but I guess selected for the tolerance. Of course that's when new, what the drift may be over time I don't know. Add a 1k 0.1% resistor and you have a reasonably accurate 5mA DC current...though don't forget the meter will have some internal resistance.


I suppose you just check against a known power supply you have used ,a 1 % 5v regulator most of the time they are with in half a volt but if thats my meter i see your point

That's all fine and well for DC low-voltage and current, but what about higher figures? Then AC? It's a specialised industry, one I admit I know little about.


I am happier with Dc readings i have to admit !

One of the easiest is time or its inverse, frequency. Even the cheapest crystal is far better than 0.1%. Get a GPS receiver and the 1 pulse-per-second output is often within 10ns (nano-seconds) of UTC time, 0.000001% That figure gets better over a longer period of time. Today you can have an atomic-standard time reference in your home for just a few dollars.

But that doesn't fix our multimeter or 'scope issues.

Steve A.
[/quote]

I can see a future where you pc would be your every thing scope meter so on ,perhaps we need an on line scope multi meter with a standard input device that way leave the calibrating to the server ! :wink:
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 Apr 05, 2020 5:11 pm

OK i finished today's work i added the extra caps and resistors Klaas suggested wacked another 2 1000 volt diodes in also .
Results below voltages something there should be well within range now i m looking at the 1400 and expecting 200 volt drop with a load 1200 volts ...as i mentioned before if you use any thing over 1400v you more than likely will get sparking killing something wired in the wrong spot .
I also finished the dual 12 volt supply every tested working
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I now need the positive 300's 400 volt anode and deflection amplifier voltage ...i can use another transformer or derive it for the 800 v AC if possible \ looks like it might but i wouldn't use the doubling idea as below
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I forgot the resistors across the Positive side transformer caps to discharge them i will update it .
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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 Klaas Robers » Mon Apr 06, 2020 3:23 am

Harry, you can do better, this will not work.
It depends on what you want to get.
- If you want to get +1100 volts, then you should remove the capacitors going downward to the diodes, and replace them by a wire,
- if you want to get +2200 volts, then you should add a string of diodes to ground from the point where the capacitors meet the diodes.
- And use the same amount of diodes (5) and capacitors (6) per string, as you use for the negative 2200 volt.
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Re: NBTV Television Analyst

Postby Harry Dalek » Mon Apr 06, 2020 6:08 pm

Klaas Robers wrote:Harry, you can do better, this will not work.
It depends on what you want to get.
- If you want to get +1100 volts, then you should remove the capacitors going downward to the diodes, and replace them by a wire,

Hi klaas
Well decreasing positive voltage is the aim .

Voltage wise i Need around 400 volts, a voltage drop would be good more the better closer to the circuit needs for the anodes and defection amplifiers

Sort of have to work with what the transformer gives and see whats possible manipulating the output voltages to the needs , not an ideal situation but it is what it is .

Thinking more like this idea klaas to drop voltages ? the resistor cap idea in this circuit i suppose just to match the capacitor working voltage range again use 3 for the 1000 volts expected
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Last edited by Harry Dalek on Tue Apr 07, 2020 8:00 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: NBTV Television Analyst

Postby Steve Anderson » Mon Apr 06, 2020 7:49 pm

Harry, if you're using the same type of CRTs as before (and two of them) why not use exactly the same power and deflection arrangement as before. It worked, why go through all this again?...unless I've missed something...there are only so many ways this can be done....a bit like skinning a cat....except less messy!

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