[ARC5] Strange box - Pictures

[WA5CAB at cs.com]

Actually, no.  As Gordon mentioned earlier, the well made parts inside the 
black box are the guts out of one of the VHF Command Set receivers, probably the 
R-28/ARC-5.  I finally got around to going into the attic and getting AN 
08-10-195 Volume 2 (VHF Components).  Everything in the upper photo except the 
trashy power supply related components, speaker, coax, 6V6GT and box matches 
Figure 19 and Figure 20 - VHF Receiver - Right Side.  Everything in the second 
photo except for the previously mentioned exceptions matches Figure 21 and 22 - 
VHF Receiver Left Side.

Someone gutted an R-28 (or maybe a BC-942).

The domed plugs in the top of the 6.9 MC IF transformers are just sheet metal 
hole plugs (with fingers in the holes).  Same function as the black plastic 
ones commonly seen today.  They were fitted to protect the tuning adjustments 
from casual tampering and dust or other contamination.  As were the aluminum or 
plastic caps on top of the IF transformers in the HF and MF receivers.

Incidentally, frost plugs, or freeze plugs as they are called up here, aren't 
really there to protect a cylinder block from freezing.  This is an almost 
universally accepted urban myth dating back to well before anyone on this list 
was born.  The holes being plugged were mostly vent holes during the casting 
process, required to successfully cast a cylinder block with integral water 
jacket.  The fact that they often pop out if the coolant in the block is allowed 
to freeze probably led to the myth.  But the block invariably cracks anyway.  
In other cases, the plugs cover holes required during internal machining of for 
example oil galleries, after which the holes need to be plugged to prevent 
lube oil from leaking out.  In better quality engines such as the 2-1/4 litre 
Land Rover, threaded aluminum plugs were used in most vent holes and threaded 
steel ones over the oil galleries.

In a message dated 10/23/2005 10:42:52 PM Central Daylight Time, 
neilba at clear.net.nz writes: 
> My guess:
> A very early (circa 1950) TV tuner connected
> to a rebuilt ARC-5 IF strip.  The latter possibly
> the 2830 KHz version from the 6-9.1 Mc unit.
> 
> What for?  To tune into the Police comms which
> were on about 40 MHz in the 1950's and 60's.
> 
> The domes on top of the IF cans appear to be
> vehicle frost plugs (not sure if that is the US term,
> they rupture if the water freezes in the engine
> block) , but why are they fitted?  To stop people
> from tampering with the alignment?
> 

Robert Downs - Houston
<http://www.wa5cab.com> (Web Store)
MVPA 9480
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