On Feb 2, 6:48*pm, "Richard Knoppow" wrote:
"K3HVG" wrote in message

...



Jim Haynes wrote:
Maybe we need to discuss what you really want to
accomplish.

My experience with T-17 microphones 50 years ago is that
they are
just not very sensitive. *I assumed this is deliberate -
to make
yourself heard over the noise in an airplane you have to
yell into
the mike.

Now if you want to preserve an authentic T-17 then I
guess something
like baking the transmitter is about your only hope, and
you can only
hope to make the mike as good as it was when originally
manufactured.

I remember lots of guys in the old days, who were not
interested in
historic preservation, simply took the carbon element out
of the
T-17 and attached the wires to a Western Electric F-1
element and taped
it in place. *F-1 was the element used in the 302
telephones, forerunner
of the later T-1 used in the 500 type sets.

If you want to preserve the appearance of the T-17 but
not the
authenticity, then maybe you could get the original
element out and
replace it with either a T-1 or an electret mike behind
the faceplate
and nobody will know the difference (except you will
sound a lot
better on the radio).

I was working with some military handsets a while back
that use the
equivalent of a T-1, and replaced the old transmitters
with new T-1s.
I also got an electret T-1 replacement from Mike
Sandman - it was
designed for use with a modular-corded handset, but with
a little
hacking I got it to fit into the older kind of handset.

Has anyone worked out the circuit to use an electret like
you get from
Radio Shack - they have 2 and 3 terminal models - to
replace a carbon
element?

Jim W6JVE

Jim, *I'm surprised you didn't need an amplifier with that
electret element? *That's what the carbon-compatible mics
use in 2-way and avionic installations to get the required
output level and the correct low-Z. *Also, the larger
telephone elements won't fit inside the T-17 housing and
would have to be mounted, up front, as you mentioned. *I
did a military mic article for the June 2007 issue of
Electric Radio, if anyone's interested. *DE K3HVG

* * Since T-1 elements are fairly plentiful one can get the
carbon granules out of one to repack the T-17. I did this a
long time ago to repack a Western Electric 375 double-button
broadcast mic. It worked fine but was, of course, tedious.
* * Where the original carbon granules have been fused due
to excessive current (too much voltage) simply drying them
out will not fix them, they must be replaced. I don't
remember how the T-17 element is constructed but most carbon
mics are made so that replacing the carbon can be done.

--

--
Richard Knoppow
Los Angeles
WB6KBL
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Yeah; doesn't 12 volts sound a bit high? While approx 100 ohms plus
1200 phms = 1300 ohms and therefore 12/13000 = about 9 mlliamps
current, just wondering if a combination of packing, moisture and
maybe a bit of carbon granule sparking at too high an energising
voltage could be contributing to the problem?
Energising voltage of around 3 volts was typical in many dry cell
telephones sets; or even on sets where 48 volts is/was fed out from
the telephone Central office .