[Boatanchors] When You Can't Get an IF Can
Bill Cromwell
wrcromwell at gmail.com
Tue Sep 29 08:24:23 EDT 2020
Hi Dave,
I have a radio that uses those tubes (but not quite the same) and it has
an open primary in one of the IF cans. It's 455 kc like yours. That is a
lot of fine wire. I have tried rewinding a couple of them (long, long
ago). It didn't turn out well. I have found a couple of them that were
burned off/broken at the terminal lead and I was able to repair those. I
have doubts about the Q of the ceramic resonators (I played with some)
and the unyielding center frequency. You can't align them with your
golden screwdriver or diddle stick.
I have considered using an IF can from a transistor radio and inserting
the primary (or secondary - reversed) in the cathode lead instead of the
plate supply. I see the DC blocking cap(s) and rf choke. That might also
work with the Transistor IF can. You might also try an IF can from an
AA5 if there is room. That would allow you to try to align it. The
transistor version is for lower impedance circuits on the secondaries
and the output circuits of cathode followers are low impedance.
Reversing the windings might accommodate that. The can will also not be
exposed The tube B+. The transistor radio IF cans probably won't
tolerate being in the plate circuit. But maybe. May or may not work anyway.
I think I have a tube IF can for 455 kc here if I didn't already donate
it to somebody. If you have room for one of those I will look for it.
73,
Bill KU8H
bark less - wag more
On 9/29/20 7:26 AM, David Stinson wrote:
> Good Morning.
> Theoretical situation-
> You have an IF transformer with an open primary.
> For whatever reason, you cannot get a replacement
> or suitable substitute. Some of you will recognize
> this diagram:
>
> https://photos.app.goo.gl/qtLG7oEEP73Lg7Yt6
>
> Possible solution:
> Use a 455 KC Ceramic Resonator-
>
> https://photos.app.goo.gl/SbYwxAEzubXCkGU27
>
> The 10 Ohm resistor is because that was the DC
> resistance of the secondary winding.
>
> Thoughts?
>
> 73 DE Dave AB5S
>
>
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