[Collins] 75A-3

[Dr. Gerald N. Johnson]

Consider that the factory probably changed the circuits at SN1300 so the 
mod for the later radios was different than the early radios and that 
the mod bulletins were issued well after SN1300 was shipped. They did 
such things with the A4 and caused the retail and street values to be 
different according to the serial number. Art  didn't like that and so 
he decreed that the S line serial numbers were to be issued in random 
order and they were. Though MCN (Manufacturing Change Numbers), model 
numbers, and logo styles (winged, meat ball, and after he lost control 
Rockwell) show some different vintages. Makes for difficult tracking of 
circuit changes which were considerable in the S line as well as the KWM-2.

73, Jerry, K0CQ, Technical Adviser to the Collins Radio Association

On 1/16/2012 1:59 PM, Ron Youvan wrote:
>     Joe Walden wrote:
> /*snip*/
>>    My question today is
>> about some mods that Collins sent out back in the 1950S...  I have these
>> three bulletins...  Bulletin #1 is a mod to reduce internal noise and
>> improve the signal to noise ratio under average operation conditions..
>> Bulletin #2 is for receivers serial #1300 and over.    Bulletin #3 is for
>> receivers serial #1299 and below..  My receiver is serial #391..  This
>> bulletin concerns a 2 to 1 improvement in the cross modulation and blocking
>> characteristics...  Should I make these modifications in bulletins #1 and
>> bulletin #3???
>
>     In my personal experience there is no such thing as a bulletin to be applied to a range of after
> a certain number, this sounds like a typo to me.  When a bulletin is published it would apply to
> units previously made, not future units, those they do at the factory.