[Milsurplus] BC-347-A Interphone question

[Michael Hanz]

That's actually a pretty good guess, except that in the case of the 
holes in the BC-347-*, they are not always in the corners and the 
construction is die cast, with two opposite corners having an integral 
boss that is threaded for the two assembly screws.  See attached photo 
of back.  With four holes in the back and two in the lower front, you 
can mount the amplifier either vertically or horizontally and always 
have four holes available to drain water.  I took a few minutes to look 
for an example of one of the weephole advisories, and the first one of 
several that popped out was this one from The Airborne Radio Maintenance 
Notes dated November 1945, in this case for the associated BC-366 jack box.
73,  Mike  KC4TOS





On 2/9/2019 11:52 AM, John Hutchins wrote:
>
> I am shooting for bending holes when forming rectangle boxes SOP for 
> metal work
>
> On 2/8/2019 9:12 PM, Michael Hanz wrote:
>> Moisture relief.  In a closed box that is not hermetically sealed, 
>> one that experiences external temperature and humidity changes over a 
>> 24 hour period, you need to have some way to "level" the humidity 
>> inside the box.  Failure to do so means that condensed water inside 
>> the box keeps increasing over time.  There are numerous tech 
>> bulletins issued about drilling such holes for aircraft control boxes 
>> and the like.
>>
>>         73,
>> -Mike KC4TOS
>>
>>     ----- Original Message -----
>>     *From:* Hubert Miller <mailto:kargo_cult at msn.com>
>>     *To:* milsurplus at qth.net <mailto:milsurplus at qth.net>
>>     *Sent:* Friday, February 08, 2019 17:03
>>     *Subject:* [Milsurplus] BC-347-A Interphone question
>>
>>     I was looking at a new unissued, in original packing BC-347-A
>>     interphone amplifier.
>>     Looking at the back side, I see in each of four corners, but not
>>     rigorously in the same exact position for each corner, a
>>     wire-sized hole.
>>
>>     The first time I noted this, on a used BC-347-A, I thought, aha,
>>     someone wanted to run wires into it, for a ham hack.
>>
>>     But this new one has the same.
>>
>>     What are these holes about ? They are ungrommeted, so any wire
>>     transiting would be abraded.
>>
>>     thanks-
>>
>>     Hue
>>
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-- 
Michael Hanz - KC4TOS

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