D-104 microphones with the amplifier in the base work just fine with
modern rigs. Look at the bottom of the microphone - if it has a hole
with an adjustable potentiometer below the hole, it has the amplifier.
The Heil rebuild kit is not needed unless the mic element is bad. The
frequency shaping of the Astatic mic element is very similar to the Heil
HC-5 mic element, but the Astatic element needs to work into a high
impedance (100k to 1 megohm) to preserve that shaping. In an all-tube
transmitter, that high impedance was presented by the grid of the
microphone amplifier.
Those D-104 mics with an amplifier will work into a much lower impedance
mic input without any change.
The old crystal elements could go bad if exposed to temperature extremes
or rough handling, but the more common ceramic elements are practically
indestructible. Astatic made these microphones over a long period of
time dating back to the 1950s or before, and there were changes from
time to time.
73,
Don W3FPR
On 1/28/2014 8:40 AM, John Fritze wrote:
I am currently in the middle of converting a D-104 Eagle into a usable mic
and have had a bit of experience in the past with them. I am trying to
recapture a bit of the nostalgia from my early ham days. I paid too much
for it, but not only is the chrome flawless, but it came with the original
box which surprisingly is in really good condition.
Anyway what Don says is true, there were several models and until you
dismantle it you will not know what one you have. BUT on the plus side,
when I removed the bottom plate, "looky-looky" there was a schematic
diagram pasted to the inside with the wire colors for my model listed. My
mic had a large element (probably carbon) and an amplifier circuit with 9V
battery (still in there---yuck) in the base. So remove the bottom, and if
there is no schematic, but your mic sounds like it is the same model I
described, let me know and I will try to send you a picture of the
schematic.
I ordered a Heil 5.1 rebuild kit from: * http://www.dxstore.com/heil_parts.html
<http://www.dxstore.com/heil_parts.html> * for $50. I needed some small
parts for several of my older head sets like foam pads and so forth, so
perfect timing.
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