[ARC5] T-17 Metal 1942 or Plastic 1944 for 1949 GRC-9?

[Richard Knoppow]

    I was thinking of that. I am not sure I have a decent telephone 
element to sacrifice.  In the past I was able to repair a couple of 
antique double-button broadcast type microphones this way.  I am not 
sure what happens to the carbon. I've seen some technical papers on it, 
I think in the BSTJ. Certainly they can absorb moisture and also get 
burned by excessive current. Sometimes you can fix the former by baking 
them but I think once burned they must be replaced.
     Bell System recycled everything they could so I can believe they 
refurbished microphone elements.
     BTW, an old friend, long SK, who was a sound engineer at NBC made a 
recording of the Tonight Show orchestra using a Western Electric 
double-button carbon mic. It was quite astonishingly good sounding, much 
like a big condenser mic although of course noisier.  I think I may have 
a cassette of that still.

On 9/15/2016 8:47 PM, hwhall at compuserve.com wrote:
> Since you know now how to open up the granules cup, you might try
> cannibalizing a phone element for its granules and try swapping them.
> I've heard of at least one person that replaced old carbon mike granules
> that way with some success. I know there was an old WE (I think)
> advertisment showing they refurbished elements with new carbon.
>
> Wayne
> WB4OGM
>
> -----Original Message-----
> From: Richard Knoppow <1oldlens1 at ix.netcom.com>
> To: hwhall <hwhall at compuserve.com>; arc5 <arc5 at mailman.qth.net>
> Sent: Thu, Sep 15, 2016 9:19 pm
> Subject: Re: [ARC5] T-17 Metal 1942 or Plastic 1944 for 1949 GRC-9?
>
> That is possible. I used a -hp- digital meter, it probably has
> pretty low current on the ohms range. I will try it again with a Triplet
> 630A should put more current through the mic. I can also try it with a
> couple of flashlight batteries. It never worked very well. I would not
> have tried opening it if it had.
>
> On 9/15/2016 7:35 PM, hwhall at compuserve.com
> <mailto:hwhall at compuserve.com> wrote:
>>> Mine reads very high resistance, about 12K where a good carbon element
>>>should read perhaps a couple of hundred ohms.
>>
>> I think I recall that Dave discovered, on a useable T-17 button, that
>> the ohmmeter measured resistance varied a lot depending on the meter
>> used. His theory was that the newer meters passed less current thru the
>> carbon than older analog meters and since the carbon is not a fixed
>> resistance, it varied with the applied current.
>>
>> Wayne
>> WB4OGM
>
> --
> Richard Knoppow
> 1oldlens1 at ix.netcom.com <mailto:1oldlens1 at ix.netcom.com>
> WB6KBL

-- 
Richard Knoppow
1oldlens1 at ix.netcom.com
WB6KBL