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Old 19th Oct 2020, 2:01 am   #1
radiograham
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Default VCR517 base repair ideas.

Hi all, I have a VCR517 which was found to have a open circuit heater, removing the plate on the back I found that the leadout wires had broken about an inch short and when I tried to clean them to solder a wire to them they broke even shorter to about an inch long, I then removed the base to try and get at them, even then they are right up inside the glass base and I think nigh on impossible to get at, I think it is a lost cause unless anybody has any ideas? Graham.
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Old 19th Oct 2020, 8:07 am   #2
M0FYA Andy
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Default Re: Vcr517 base repair ideas.

I understand the problem, they are made of a hard springy metal. Would it be possible to extend them using the inserts from a 'chocolate block', then insulate with heatshrink?

Andy
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Old 19th Oct 2020, 9:17 am   #3
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Default Re: Vcr517 base repair ideas.

Or cut down a multiway pin-header type of connector as used on PC motherboards etc. Depends on the plating on the wire I guess.
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Old 19th Oct 2020, 9:24 am   #4
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Default Re: Vcr517 base repair ideas.

The wires will be an alloy chosen to match the thermal expansion of glass, to keep the seals hermetic. Kovar, perhaps. Not easy to solder to, and after 75 years of tarnishing, even harder.

If Richard's suggestion of a crimp out of a header connector doesn't work, then I think it's had it as it'll just keep breaking off right back to the seal if the wire has gone brittle.

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Old 19th Oct 2020, 9:58 am   #5
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Default Re: Vcr517 base repair ideas.

I seem to recall oldticktock making a repair to a CRT by grinding back the glass making a mechanical joint using thin wire then covering it in silver loaded rear windscreen repair paint.

I will see if I can find the thread it may have been here or VRAT.

OK I found it here

https://www.vintage-radio.net/forum/...ad.php?t=70110

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Old 19th Oct 2020, 10:09 am   #6
M0FYA Andy
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Default Re: Vcr517 base repair ideas.

That's why I suggested a screw-down fitting, to avoid the forces of crimping (and getting a crimp-tool in there) and the difficulty of soldering.

Andy
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Old 19th Oct 2020, 11:54 am   #7
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Default Re: VCR517 base repair ideas.

There shouldn't be any crimping involved. Use a spare ready made assembly complete with flexible wire attached and just cut it down to one way. Push the one-way connector onto the exposed wire and hope the friction is enough to remove any tarnishing and make contact.
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Old 19th Oct 2020, 12:07 pm   #8
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Default Re: VCR517 base repair ideas.

I just re-read the post and I see the problem the wire is up inside the base toward the pinch.

A push-fit as suggested by Dickie is what I think I would try.

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Old 20th Oct 2020, 1:11 am   #9
radiograham
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Default Re: Vcr517 base repair ideas.

Quote:
Originally Posted by M0FYA Andy View Post
I understand the problem, they are made of a hard springy metal. Would it be possible to extend them using the inserts from a 'chocolate block', then insulate with heatshrink?

Andy
Hi,thats what i was hoping to do when i got the base off but there is no room to get anything like that in im afraid.
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Old 20th Oct 2020, 1:33 am   #10
radiograham
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Default Re: VCR517 base repair ideas.

Thanks for the ideas,i think the only possibility is the push on connector idea as there is no room to get in there,even that will be difficult the leadout wires are very brittle and will probably break off again,will have to see.
Graham.
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Old 23rd Oct 2020, 4:09 pm   #11
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Default Re: VCR517 base repair ideas.

Kovar and Fernico seem to be Iron, Nickel and Cobalt alloys.

Can this alloy be softened by heating or quenching?
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Old 23rd Oct 2020, 10:23 pm   #12
radiograham
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Default Re: VCR517 base repair ideas.

Quote:
Originally Posted by Silicon View Post
Kovar and Fernico seem to be Iron, Nickel and Cobalt alloys.

Can this alloy be softened by heating or quenching?
Hi,maybe but the problem is the very small space to work in,i presume you mean to heat and then quench with water?the quenching part would be easy but the heating would be very difficult. Graham.
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Old 23rd Oct 2020, 10:46 pm   #13
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Default Re: VCR517 base repair ideas.

Risky close to the glass seal.

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