In article ,
David Brodbeck wrote:

Good thought! No such luck, though. Looking at the schematic, if there
were such a jumper it also would null at 200 ohms when the "range
expander" switch is on, and it doesn't.

I think when I get time I'm going to check the transformer windings for
continuity...maybe someone transmitted into it and blew a winding. It
looks from the schematic like this little toroidal transformer would be
"first in line" to get zapped.

Yup. Not an uncommon way for these devices to go to Tumbolia. The
pot might also have gotten cooked.

http://www.qsl.net/wq1rp/noisebrg.htm has a nice article on construction
of a homebrew bridge, including instructions for winding the
transformer. If yours is smoked, it ought to be relatively easy to
replace.

I built a fancier derivative of the above-mentioned circuit a couple
of years ago - one with some amount of protection built in, and a
periodic chopping oscillator which turns the output from a simple hiss
into a chuff-chuff-chuff sound (slightly easier to null out under
noisy-band conditions). The schematic and a writeup are available
in the following newsletter:

http://www.fars.k6ya.org/relay/Relay0710.pdf


--
Dave Platt AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
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