[ARC5] Metal body T-17 disassembly question

[Richard Knoppow]

    Mine is a D. It has three screws in the front cover. They were 
filled with hard wax. When they are removed the front comes off exposing 
the mechanism. Mine had low output and was noisy, typical of carbon mics 
that have been exposed to moisture. I was unable to make it work better. 
Sometimes you can replace the carbon granules with those from an old 
telephone carbon transmitter. Its also possible sometimes to restore 
operation by baking the mic for a few days at a fairly low temperature, 
say 130F. The construction of the T-17 seems to vary among manufacturers 
so some undoubtedly are less vulnerable to humidity than others.
     Another problem common to all type of carbon microphones is burning 
of the carbon granules by excessive current. They should really be run 
at the lowest current that will give you output. If the current is too 
high it will burn the points where the granules contact each other 
resulting in either very low output or nothing. The only fix for this is 
to replace the carbon. The granules can also settle and pack. This is 
very dependent on the specific construction of the mic. This results in 
low output and noise. It can often be cured by vigorous shaking or 
tapping the mic against something. Some mics are very position 
sensitive. In fact, Bell Labs did a lot of research on how to make 
telephone transmitters that were relatively insensitive to position (and 
also other common problems).

On 4/14/2017 10:48 AM, J Mcvey via ARC5 wrote:
> The paint has it blurred, but it looks like T-17-E.(the top and bottom
> of the last letter are horizontal lines)
> This one also has large seven 1/8" holes in the mouthpiece ( 6 in a
> circle and the 7th in the center.)
> The same configuration of 6 filled holes as well.
> It has a Shure SW-109 PTT.
>
>
> On Friday, April 14, 2017 12:56 PM, WA5CAB--- via ARC5
> <arc5 at mailman.qth.net> wrote:
>
>
> OK.  What suffix letter and Order Number does your particular unit
> actually have?  The three that I described are all just T-17 (no suffix
> -A, -B, etc.) and on 6490-CHI-42 or 1545-PHILA-42 Orders.  The first one
> is unusual in that it has 7 approx. 1/8" diameter holes in the center of
> the mouthpiece.  And it is also unusual in that it has 6 filled holes, 4
> @ 90 deg. with screws and 2 more in the upper quadrants that appear to
> be through holes.  The other one is typical of many I have seen with
> just the common 4 screws and the three small holes in the center.  And 3
> screws holding the back on.
>
> In a message dated 04/14/2017 10:09:16 AM Central Daylight Time,
> ac2eu at yahoo.com writes:
>> I just need that assurance that there were indeed screws under those
>> filled holes before I proceeded. There are 6 holes, but only 4 have
>> screws ( ones that are 90 degrees apart) .
>>
>>
>> On this one, the screw on the backside of the handle is for the hanger
>> loop keeper bar that holds the loop fast. The screw was missing, but
>> fortunately, the loop was stuck and didn't fall out. The thread is
>> 4-40 or at least it worked well with 4-40.
>> The mouthpiece and mike look like they were intended to be replaced as
>> a unit because the element almost fell in two pieces when I removed
>> the retainer clip and dug it out.  luckily that didn't happen or I
>> would have had a carbon mess to clean up.
>>
>>
>>
>> The switch comes out easily by removing the sub-assembly's retaining
>> screw on the handle.
>
>
> Robert & Susan Downs - Houston
> wa5cab dot com (Web Store)
> MVPA 9480
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-- 
Richard Knoppow
1oldlens1 at ix.netcom.com
WB6KBL