[ARC5] ARC-5 Transmitter questions

[Mike Hanz]

The shrunken windows on command transmitters fall into two 
categories, conventional engraving with a white filler (SCR-274N and ATA 
windows) and the ARC-5 transmitters, which have a white 0-50 
scale applied to the back along the bottom edge.  The latter scale has a 
definite thickness - about a mil or two, but I haven't bothered to 
research the fabrication method because there seem to be enough parts 
units around to make reproduction unnecessary.  Sometime in 1944 
they appear to have changed the material from a celluloid or cellulose 
acetate based plastic to acrylic, and that change solved the problem for 
both the 274N and ARC-5 transmitters still in production.  I've sheared 
out a stack of the .062" thick windows from acrylic for later engraving 
someday, but have never gotten around to setting up the engraver.  It 
would be a snap with clear film and a laser printer that had white 
toner.  :-)

The aluminum manufacturer dye markings on the bottom of receiver and 
transmitter covers are quite common, and I've seen them on NOS units 
straight out of the box.  In fact, the only ones I can think of that 
don't have them are pretty rare examples of low volume prototypes like 
the R-112, R-113, T-89, and T-90/ARC-5, and the small production run 
T-15, T-16, and T-17 MF transmitters.  The RAT and RAV receivers I've 
looked at don't seem to have them either.  The markings come off with 
little effort, so even those may be suspect, but at least that finishing 
touch would be consistent with low volume or essentially hand-built sets 
whose purpose includes evaluation.

Best wishes,
Mike

> Does anyone know if there is a supplier of replacement plastic windows for the
> roll-a-ductor in the ARC-5 Tx's? Mine has shrunk with age. It would seem to be a
> pretty straight forward thing to make, since it's a piece of clear plastic (
> probably acetate)  with the white markings screened on.
> 
> Also, the bottom cover of my Tx has mill markings "ALCOA" and "3S-1/2H". Does
> anyone know if this is an original cover, or if it's someone's home brew
> replacement? It's nicely made with the original type screw posts. I would be
> surprised if the red ink mill marking would have survived the factory finishing
> process.