[Collins] Help: Collins 75A1 Wiring don't Match Schematic

[Glen Zook]

Methinks you mean the 75A-4, not the 75A-1.  It was the 75A-4 serial number valuation that got Art riled up and had the S-Line, and KWM-2- series, serial numbers scrambled.


Just like all of the Collins amateur radio equipment, there were definitely changes made during the production life of the 75A-1.  There are a couple of different versions of the manual on the CCA website.  One of the different schematics is at 

http://www.collinsradio.org/wp-content/uploads/2012/04/75A-1-Schematc.pdf



Another is contained in the complete manual available at:


http://www.collinsradio.org/wp-content/uploads/2012/04/75A-13rd-ed-10-48.pdf



There were also several Service Bulletins for the 75A-1 and these can be downloaded at:


http://collinsradio.org/archives/manuals/75A-1_SB_2.pdf



http://collinsradio.org/archives/manuals/75A-1_SB_3.pdf



http://collinsradio.org/archives/manuals/75A-1_SB_4.pdf



 Glen, K9STH 
Website: http://k9sth.net

      From: Dr. Gerald N. Johnson <geraldj at netins.net>
 To: collins at mailman.qth.net 
 Sent: Thursday, July 19, 2018 8:44 PM
 Subject: Re: [Collins] Help: Collins 75A1 Wiring don't Match Schematic
   
There were a number of changes in the first thousand or so 75A-1. So 
many that made the revised receiver work better and that made the 
dealers charge a lower price for low serial numbers and a higher price 
for later factory revised radios. I don't know how well the revisions 
have been documented and whether the first edition of the manual matched 
the earliest radios. There might actually be some service letters about 
the changes so sellrs and owners of early radios could have made the 
modifications. I'd go look at the data collection on the Collins 
Collector's Association data site.

The pricing annoyed Art so after a year or two of S-line production he 
decreed that S-line serial numbers shall be issued in random order which 
they were. However model changes and trim changes showed differences but 
the S-line radios didn't have the history of so many effective revisions 
as the 75A-1.