[Collins] Collins Serial Numbers.

[Dr. Gerald N. Johnson, electrical engineer]

In my Collins experience, engineering models started with serial number
1, but production started with sn 101. That might mean the sn 23 and sn
36 were the earliest found, though its likely the earliest spent much
time in management hamshacks being proven and eventually snuck out to
some developer's hamshack or was donated to a school like Iowa State.
Very early radios, especially early engineering models probably used
paint on rubber stamps for part identification, not silk screens, but
later engineering models would be using silk screens just like
production radios. The corners of the rubber stamps were probably
sharper than the apertures on the silk screens, though the silk screen
labels should be more parallel to each other and the sides of the
chassis. Stamped paint will vary in letter/number spacing and paint
density, while silk screened component identification will be more
consistent in weight of paint.

The 75S-1 and 75S-2 are IDENTICAL except for the added crystal board,
its switch, and the escutcheon. Some were built that way, some were
converted in the factory, some were converted in the field. There was a
kit made for the purpose. The same thing applied to the KWM-2 to KWM-2A
(different kits only for the different escutcheon engraving),
32SS-1/32S-2, 75S-3/75S-3A 75S-3B/75S-3C. Radios converted in the field
probably won't have the inspection dots on the solder connections.
Radios built or converted in the factory will and only the production
log, if it still exists, can tell which radio was built or converted in
the factory or service department. There are some example escutcheons
found where the A was engraved in an existing escutcheon when the
replacement escutcheon wasn't handy making the model number off
centered.

I'm sure sometimes there were groups made with the extra crystal board
for large orders and those serial numbers (before the randomization of
serial numbers) would be grouped together. Otherwise probably normal
sales requested a few to be built with the extended coverage per week
and the kits were mixed in with regular production. When a huge order
for extended coverage came in, probably all on the production line were
built with extended coverage as well as a collection from finished stock
were unwrapped and converted. At best there might be a subtle hint of
the difference. Factory built probably have an ink stamped or stamped
serial number tag, its possible that converted radios will have the
serial number written into the tag by hand rather than stamped.

Sometime during S-line production for sure before 1963, Art decreed that
serial numbers had to be randomized. He was upset that the 75A4 value
varied even at the dealers according to serial number (and thus circuit
revisions). It wasn't a tale, I looked up the Collins component
specification for the serial number tags for the S-line and it
definitely specified the tags to be in random order. But with the model
changes and then the change from winged to round logo, Art's other
decrees set some age markers anyway.

Production rates may have been limited by plant capacity more than by
sales. I've used both KWM-2A and S-line in military post MARS stations.
I'd suspect that while the KWM-2A was easier to set up and use, the
S-line was a little more reliable needing fewer repairs because the two
cabinets could run cooler than all packed into one. But then the gaggle
of interconnect cables used with the S-line was probably its Achilles
heel when used in the tropics.

73, Jerry, K0CQ, Technical Advisor to the CRA
-- 
Entire content copyright Dr. Gerald N. Johnson, electrical engineer.
Reproduction by permission only.