On Dec 27, 6:24*pm, "Richard Knoppow" wrote:
* * *Today I bought an S-20-R which appeared to be in very
good condition. However, someone replaced the original
speaker. The problem is that the original is a field coil
type where the coil is also the power supply filter choke. I
can probably find a suitable choke but would prefer, if
possible, to find an original speaker. One in working
condition is, of course, ideal, but one with a working field
coil and matching transformer is acceptable because I can
almost certainly get it re-coned locally. Other than that
the thing seems to be in good condition and sort of works.
* * *Please respond via personal e-mail. The address below
is on a spam-blocker but I will unblock you. I can also be
reached through the ARRL forwarder in the usual way (my call
@ ARRL.org).
* * *This is an example of total impulse buying:-(

--
Well, as I sometimes do, I yelled for help too soon. A bit of
research shows that the later S-40A is nearly identical to the S-20R
and later versions of the S-40 are not much different. All use a
straight RC filter in the power supply with a 1500 ohm resistor in
place of the speaker field (which is also 1500 ohms DC resistance).
That is exactly the way this RX is modified so there does not appear
to be any advantage in trying to find an original speaker assembly.
While I still need to do some detailing on this little guy it seems to
work very well and is surprisingly good sounding.