The Tasmanian Devil VCR139....A for Andrew

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The Tasmanian Devil VCR139....A for Andrew

Postby Harry Dalek » Sun May 21, 2017 12:05 am

I am at the moment Studying the VCR139A CRT that Andrew kindy got me from hes recycling center in Tasmania .

http://www.tubecollector.org/vcr139a.htm

Does not look like it was ever fired up new in its box and packaging i have other things i am working on but love to work a bit on this too .

I see this tube runs much lower than my past 3Bp1 and to me has an unusual 4 volt heater supply .

Have been thinking about what i would like this to do which i suppose depends on how well it can be focused ...size of the raster dot ....

What i have in mind is running this at 60 line to a high range of Steve O's Argus ...i might be getting to ambitious here but one can dream !

The idea i have come up with is any thing over a line rate i don't have a video signal for is to use a boxed in flying spot camera as in a side test card on the screen ..cutting down on the electronics the monitors saw tooth will be fed to one of my oscilloscopes it will be used to make the raster that will scan the slide and use one of my head amps to pick up the scanned light or make one with either a PMT or solar cell have to encase light proof this i should think ...
This way no matter what line number i have the thing will always be in sync unless i am missing something .
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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 Steve Anderson » Sun May 21, 2017 1:12 pm

Now that's one CRT I don't have the datasheet for, some trawling of the 'net is required.

4V heaters were quite common in pre-WWII CRTs, or at least those designed in that time period. It was post-war that the 6,3V 'standard' became accepted...I wonder why 6.3? Why not simply 6V?

Steve A.

A quick dig around and I found these two, enough to get you going...
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VCR139A-CV1588 A.pdf
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VCR139A-ECR30 A.pdf
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Re: The Tasmanian Devil VCR139....A for Andrew

Postby Harry Dalek » Sun May 21, 2017 6:33 pm

Steve Anderson wrote:Now that's one CRT I don't have the datasheet for, some trawling of the 'net is required.


Hi Steve
Yes this is a hard one to get data information on ! i did come across some scope builds with it and saw there are equivalents with a different code lettering numbering suppose one is American other European thanks for your data sheets i didn't have those .

4V heaters were quite common in pre-WWII CRTs, or at least those designed in that time period. It was post-war that the 6,3V 'standard' became accepted...I wonder why 6.3? Why not simply 6V?


We talked about using a DC supply for the heaters a while back and i don't think you were really in favour of it .......dropping the 6.7 volt supply my transformer gives to 4 volts doing this with a 1 watt resistor or two in series one for each heater connection some sav this is better to balance it out .

Steve A.

A quick dig around and I found these two, enough to get you going...


Thank you there Steve i didn't have those .

At the moment i have cabled in the AC supply used also for the 3PB1 and SSTV monitor so much easier not having to do a AC supply for every new build and just plugging it in ...mounted the CRT for now i will have to take it out again to drill holes for controls and such just want to work this out today ..
Its a tiny little CRT does give me even in this small case more than enough room for circuit boards .

I'll post up some info i have on the tube next next that i have tracked down.
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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 Klaas Robers » Sun May 21, 2017 6:51 pm

I always assumed that the voltage of one lead-acid cell under light load is 2.1 volt. Three cells in series is 6.3.
It is the first tube developer that decided to call it 6.3 volt, then all others followed. Although very few of those tubes will have burnt on accumulator DC, this will be the explanation.

However.... my WS-19, built in 1943, and many more WW2 military wireless sets, were designed to run from a "car" battery, 12.6 volt DC.
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Re: The Tasmanian Devil VCR139....A for Andrew

Postby Harry Dalek » Sun May 21, 2017 7:27 pm

Theres Practical-Television-1964-10 11 and 12 has the VCR139A in this as The videoscope TV oscilloscope i just found the last two issues so i need to read them as well...seems to be run on minimum voltage range from a quick look ,
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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 Steve Anderson » Sun May 21, 2017 7:43 pm

Klaas, yes that may be one explanation for 6.3V. Something I hadn't considered. The acceptable tolerance was quite wide so as the batteries discharged things would continue working to an reasonable level of performance. Anyway, it stuck, as did 12.6V and all those series connected devices with either 300mA or 100mA heaters, though not seen them for CRTs...thankully...kinda hard to arrange a series connected CRT heater with the heater-cathode voltage limitations. But I guess someone managed it.

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

Postby Harry Dalek » Sun May 21, 2017 7:46 pm

Heres another i have found The Investigator oscilloscope Practical Electronics july august 1967 and an example build .
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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 » Sun May 21, 2017 8:02 pm

Some other bits ,have found stuff on the vcr97 and 138A but this is about all on the VCR139A managed to find so far ..do a bit of reading and this might help some one else that finds one of these CRT's in the future and perhaps by the end of the construction i might have something to show as well.
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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 » Mon May 22, 2017 10:29 pm

Looked at the heater Conductivity today and i was happy that it is fine ..
I tested with a 3 volt ac supply from another AC power supply and the heater lights up so i would say the CRT is fine as far as the heater gos .
But i have a problem a dilemma 4 volt heater but 6.7 volt supply .....i was thinking i could drop this with a resistor the resistor to drop it to 4 volts or 3.7 volts is 3 meg i did not notice it lighting up so i must have this wrong i will double check this .
I could do it with a DC supply ...
The heater is a pretty critical thing to get right any ideas :?:
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 Klaas Robers » Mon May 22, 2017 11:50 pm

The heater is 4V at 1.1A, isn't it?

Then you need a voltage drop of 6.7V - 4V = 2.7 volts at 1.1A

Ohm law:
So the series resistor must be 2.7 / 1.1 = 2.45 ohm. Two resistors of 1.2 ohm in series or two of 4.7 ohm parallel is close enough to 2.45 ohm.
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Re: The Tasmanian Devil VCR139....A for Andrew

Postby Harry Dalek » Tue May 23, 2017 6:31 pm

Klaas Robers wrote:The heater is 4V at 1.1A, isn't it?

Then you need a voltage drop of 6.7V - 4V = 2.7 volts at 1.1A

Ohm law:
So the series resistor must be 2.7 / 1.1 = 2.45 ohm. Two resistors of 1.2 ohm in series or two of 4.7 ohm parallel is close enough to 2.45 ohm.


Hi Klaas

I tested first using a little light globe think its 6.3 volts but showed me the voltage drop with that and the series resistor my mistake not using the heater in the circuit .
Doing the test again this afternoon with the series resistors at your values and heater load its pretty much showing 4 volts across the heater ,,,i was very cautious i only have one.
Thanks for the help there Klass
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 » Thu May 25, 2017 3:01 pm

I started working on the power supply ...the other examples of the power supply circuits i have seen to run the tube are more at what is handy with lower voltages data is saying 800 ...and 1000 maximum so i am looking at around the 800 volts.

I went with Steves original smaller 3bp1 power supply circuit looked like a good starting point i hope /

I am just working on the negative side of the power supply today the circuit pretty much gives negative 1400 volts as is in the schematic and a test it sure does ..So i am going to only use half the transformer windings for the negative supply so its giving negative 754 volts with those load resistors on a test today.
I have changed the 240 AC thats to ground in the schematic thats not connected at the moment i will use that for the positive side supply later i have grounded the center tap zero of the transformer so only using 240 volts not 480 AC as before .

That power supply board will fit below the CRT flat in the case and the other circuits on a large board either side just see how i go might only need one ,

Heres some old CRT tube data i came across
http://www.sphere.bc.ca/test/crt-data.html
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CRT-data.pdf
Wireless World 1947, 1948 CRT DATA
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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 Steve Anderson » Thu May 25, 2017 4:05 pm

Well done Harry. It could be simplified to eliminate a few of the power supply capacitors and resistors due to the lower voltage, but if you've already built it and it works to your satisfaction, leave it be.

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

Postby Harry Dalek » Thu May 25, 2017 5:27 pm

Steve Anderson wrote:Well done Harry. It could be simplified to eliminate a few of the power supply capacitors and resistors due to the lower voltage, but if you've already built it and it works to your satisfaction, leave it be.

Steve A.


Hi Steve

It was a bit of a toss up as to what voltage works best theres a bit of a range in the oscilloscopes power supplies i have looked at so just gone with data working voltage or its close enough as a tv raster it will have to be brighter than a scope trace .

I was thinking better have to much than not enough adjust it if its to high so went with your circuit.

I recalled you mentioned its best to run at the data operating voltages even if it will work on a lower voltage as it seems this one will ..

Its funny this circuit as left original was giving better results than the first try at it for the 3bp1 ..same AC supply and batch of caps even the resistors pretty much from the same batch ...i recall we had to add another stage last time ...OH well one of those things .

Keeping my self safe here these voltages are still nasty .

I was skipping ahead just thinking about the modulation side in my head i suppose the opto coupler would still be fine for 120 line its data says it has a maximum operating frequency of 500khz ,i have noticed some that have used transistor via a high voltage capacitor to the control grid mainly for 625 line so this method must have a much wider operating bandwidth 6 MHZ...since i have not noticed you using this i would think your not keen on it ?

Just trying to retrace my steps here on what i think will perhaps work still on this one as i know it can't be the same i would like it to do 60 120 line at least ...standards are of cause a problem to as to horizontal scan vertical scan differences .
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 » Thu May 25, 2017 5:50 pm

In general you should be able to adapt all of the 3BP1 circuits to the VCR139A, it's much the same as any CRT from that era. You just need to adjust some voltages here and there, I'm confident you can do that, but if you get stuck...well, you know where others and I are...

Yes, the opto-isolator should be good for up to a few hundred kHz, beyond that, say 405/525/625, a faster device would be required. Though on a 3" screen it's doubtful if you would see any difference. !20/128 lines (SSTV) is about the limit on a 3" screen. Even at 72 lines as I did a few years back, the lines are starting to merge with each other.

Capacitor coupling to the CRT grid (or sometimes cathode) means you lose your black level, it works but it's a 'cheap charlie' way of doing it.

Remember, DO NOT apply power to the CRT, or as a minimum power the heater, until you have confirmed all voltages and waveforms on the CRT socket are correct...you only have one example of this tube. It's not a BC547...

Steve A.
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