[HomeBrew] Magic Eye/S-20R musings

[Phil T.]

Thanks for the link Cal.  Looks like a great project.

The only minor concern I see with the project is that the voltage doubler 
is likely to provide  16 to 18 volts DC for the 1629 filament - guaranteed 
to shorten the life of a 12.6V tube dramatically. Now that isn't going to 
matter much if the radio is only used for a few hours here and there. But 
we should be aware of it just the same.

Phil

At 03:55 PM 8/11/2002 -0700, you wrote:
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>
>All you BA enthusiasts out there:
>
>I just helped a good friend of mine, Bernie, another ham BA 
>enthusiast,  construct a magic eye (1629) based tuning indicator for his 
>S20R. You can find this project at http://antiqueradio.org/magiceye.htm
>
>Just ensure that when you start the project, you have ALL the parts. 
>Unfortunately, we didn't have everything that we should have and the 
>project was delayed by another couple of hour trying to located two 10 meg 
>resistors and anothe 1 meg we forgot to get during the parts run.
>
>One of the interesting parts about this project was the use of the voltage 
>doubler to get the 1629 magic eye tube to work. 6.3VAC doesn't cut it for 
>this tube (which is a variation of the 6E5/6U5). It is a 12.6 fil jobbie 
>that was used (I think) in military equipment.
>
>The initial construction (which began around  an octal socket) was 
>intented to be a little organized but by the time I was done, I ended up 
>"dead bug construction" placement of many of the last components. But, she 
>worked beautifully (after I had to troubleshoot the reason why we couldn't 
>get filament voltage from a loose wire!).
>
>We didn't have a five pin plug or tube to bust up so I ended up plugging 
>in the wires as is. So, as long as it works, that' s o.k. Per the article, 
>we had to tap the AVC line. The best spot to do this (and double check a 
>tube book and schematic) was to take pin 5 of the 6H6 socket and solder in 
>a wire and trace that to the unused pin at pin 3.
>
>FWIW for a nice weekend homebrew project,
>
>Cal, N6KYR
>
>
>
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