[AMRadio] Re: D-104 hardware

[D. Chester]

> I'm trying to put my old D-104 back together.
> I've go everything except the screws that hold the front
> and back covers in place.
> Does anyone have a junker D-104 laying around
> that still has the screws.

One thing to consider is how "old" your D-104 is.  If it was made before 
1937,  the head was a full 1" thick.  Sometime that year they went to the 
familiar thinner head, that is 13/16" thick.  So the screws that held the 
older ones together will not fit the newer ones and vice versa.

Also make sure you have both ends of each screw assembly.  One end is a 
threaded hollow tube (female), and the other is a screw that fits inside 
(male).  Both male and female parts have a screw head that is seen 
externally on the assembled mic. I have seen some of these that appear to be 
identical, but some have fine threads and others coarse threads.  Make sure 
both pieces match, since you cannot mix thread sizes in the same screw 
assembly.

Another difference between the older microphone and the later version is 
that the knurling around the rim of the older version is more distinct than 
that of the newer version.  Also, the older version has screws in the back 
plate to hold a bracket that clamps down the shielded cable coming out of 
the mic, since the older version does not use the plug-in head assembly. 
The wire just comes out of the head of the older one through a brass sleeve. 
The very oldest ones also have a  large screw at the centre of the back 
plate on the head.  Evidently the earliest elements were held into place 
with a screw instead of the foam rubber and glue that hold together the more 
recent versions.  Those early versions were spring mounted inside a ring, 
just like the old double-button carbon microphones, so maybe they didn't 
think they needed to shock mount the element inside the head with foam 
rubber.  I'm not sure they even had foam rubber in 1933, when the mic first 
came out.  All the older versions I have even taken apart had a replaced 
element using foam rubber, and a nut was used to hold the large screw in 
place to stop up the hole.

For a photo of the early ring-mounted version, check out the PA0ASD web 
site.  Scroll down to the middle of the page to view the photos.  It looks 
like he was using a black lacing cord or elastic band material instead of 
metal spring to hold his.

http://www.xs4all.nl/~ort0asd/pa0asd.html

Don k4kyv