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Old 28th Feb 2015, 11:41 am   #1
Omegaman
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Default VCR139A Scope Tube

Hi All,

I'm looking for a VCR139A scope tube and tube base. A mumetal screen would also be handy if available.

I want to fulfil my childhood ambition of building a scope.

Anybody help, please?

Regards
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Old 28th Feb 2015, 12:17 pm   #2
gingpeakin
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Default Re: VCR139A Scope Tube

I've got a 5CP1 with base and mumetal screen you can have - it's a bit bigger but it's the same as a DG13-2.
I'm not sure about posting it though.

Ging
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Old 28th Feb 2015, 1:03 pm   #3
Ed_Dinning
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Default Re: VCR139A Scope Tube

Hi Howard, I have a variety of tubes up to 6" that would do for scopes as well as plenty of circuits both simple and complex, valve and transistor. You can e-mail me if you weant to discuss.
I can bring the tube to Golbourne in April if required as it will be much safer than post/ courier.

Ed
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Old 28th Feb 2015, 1:06 pm   #4
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Default Re: VCR139A Scope Tube

I've had an ACR10 stored away for a rainy day for decades, but that day probably would need to be a monsoon before I ever use it. It was reckoned to be equivalent to the VCR139A (but slightly lower anode voltages if you go by the data on the National Valve Museum site) see: http://www.r-type.org/addtext/add083.htm. It's got an unused socket as well and may be NOS (certainly looks good) but I can't test it. No mumetal shield though. Again posting could be iffy - what about FCS?

Mike
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Old 28th Feb 2015, 1:17 pm   #5
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Default Re: VCR139A Scope Tube

Howard,

There is one on Ebay at the moment, search for "WW2 ERA AIR MINISTRY STAMPED HUGE GLASS VALVE OR LIGHT BULB 13 INCHES!!"

Adrian
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Old 28th Feb 2015, 1:52 pm   #6
Ed_Dinning
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Default Re: VCR139A Scope Tube

Hi Howard, mu metal screens can be expensive and if they have been bashed may not have their full properties.
Provided you keep mains transformers well away or behind the tube you can use a steel screen fabricated from "tin" cans.

Ed
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Old 28th Feb 2015, 2:27 pm   #7
Omegaman
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Default Re: VCR139A Scope Tube

Hello,
Ging. Many thanks for the offer, but I'd like to stay to a 3" tube. The metalwork is already done.
Adrian. The one on Ebay is a VCR138, but thanks anyway.
Mike. The ACR10 looks promising, but will require modification of the circuit for the voltages.

The scope I intend to build is the PE 'Investigator', the one that Keith kindly uploaded the articles for recently.
This is the one I had my eye on since first seeing the article back in the day!
I want to build it as exactly as possible to the original design.

Ed. Thanks for that info on the mumetal screen. Points noted. I thought it may improve things by having one. I'll keep hoping something comes up for a short while before speaking with you about alternatives.

Cheers all,
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Old 28th Feb 2015, 2:37 pm   #8
Omegaman
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Default Re: VCR139A Scope Tube

I've just found a CV1588 one on Ebay.
It would appear that this is the correct one.
I still need a B12B tube base if anyone can help there.

I'll keep this post open for the moment. Just in case.....!

Cheers
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Old 28th Feb 2015, 6:48 pm   #9
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Default Re: VCR139A Scope Tube

ACR10 or VCR139A or ECR30 or CV1588, (CV279, CV964).
I think you will find that these are all exactly the same. See Wireless World Data on Ex Govt Cathode Ray tubes -Dec 1947 and August 1948, and Frank Philipse Tube data.
It just so happens that the working voltages quoted for the ACR10 in the usual tables happen to be lower. The maximum rated voltages are the same for all types. This sort of variation often happens between different manufacturers or applications.
CRT are amazingly flexible over working conditions. Set A1,A3 at the highest voltage you can produce easily within the ratings. Set Focus A2 to vary between 1/4 and 1/3 of A1,3 voltage, and adjust for smallest spot. So I would suggest build it with the voltages in the design. If it is uncontrollably bright or fuzzy, then lower the eht rail to A1/3 and focus in proportion.
A trick with the transformer is to leave it unfixed initially, and on first trials rotate it (on the mounting lugs) to minimise effects. Quoted in another of the Practical Wireless designs. wme_bill

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Old 28th Feb 2015, 6:57 pm   #10
pmmunro
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Default Re: VCR139A Scope Tube

Howard,

If a B12B base doesn't become available, have you considered making one using the contacts from more readily available valve bases - the type with two layers of SRBP?

For the insulation you could use some un-clad GRP sheet (PCB material) or another laminate such as Formica or Tufnol.

PMM
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Old 28th Feb 2015, 7:15 pm   #11
Anthony Thomas
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Default Re: VCR139A Scope Tube

For me the choice besides VCR139 would be either a 3BP1 or a 3WP1 because they both use 6.3V on the filament, the VCR139 etc use 4V 1 Amp and this I would think would be a disadvantage. Mumetal for the 3BP1 / 3WP1 are more readily available and I would be tempted to take up Eds Dinnings most generous offer of alternative CRT / base.

These days many scrapped scopes are offfered for next to nothing and the se could provide cabinett, mumetal and perhaps even power supply transformer.

Just a few thoughts to add confusion

Tony
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Old 28th Feb 2015, 7:20 pm   #12
Anthony Thomas
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Default Re: VCR139A Scope Tube

Another method of making a CRT base my dentist friend used to use was to take automotive cable connectors place them on the pins and use dental acrylic to fasten the connectors into a shape that suits the tube base. Worked for him

Tony
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Old 4th Mar 2015, 1:15 pm   #13
Omegaman
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Default Re: VCR139A Scope Tube

I have managed to obtain a tube.
I'll make a separate post for a tube base.
Thanks to all for their help and advice so far.

MODS. This thread can be closed. Thanks.
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