[Collins] 75A-3

[Carl]

Collins never made a decent AGC in any of the 75A series and it wasnt until 
the 75S3B/C they got it near perfect for SSB/CW.

I installed a SS hang AGC in my A4 in the 60's and it became like a new 
radio especially in contests and DX pileups.

All the earlier A's pump on AM and the cures have been published in ER and 
elsewhere. My A3 is now enjoyable to use along with the V2.

Carl
KM1H



Carl
KM1H


----- Original Message ----- 
From: "Jim" <jbrannig at verizon.net>
To: "Joe Walden" <w5jdy at cox.net>; <collins at mailman.qth.net>
Sent: Monday, January 16, 2012 9:32 AM
Subject: Re: [Collins] 75A-3


>I had a 75A3 and tried every modification possible to make it into a
> "modern" SSB/CW receiver.
>
> I installed the Collins Bulletins, changed mixers, added a product
> detector........
> ....none of these made it into a "silk purse" SSB receiver.
>
> Collins must have realized the same thing.  The 75A4 was a new design.
>
> The 75A3 is a nice 50's AM radio.
>
> Jim
>
>
>
>
>> Hello again from Joe w5jdy in Okla...   Thanks to the members for good
>> advice concerning the problems I had with the PTO unit and the low and
>> high
>> tunable IF's in the 75A-3 that I have been working on...  I got it from a
>> friend and it did not work..  I removed some mods that were different 
>> than
>> the manual and schematic showed and wired it according to the 
>> schematic...
>> I now have it working on all bands with good sensitivity,selectivity and
>> plenty of volume..  The PTO still won't zero on either end but is within
>> the
>> range of the error indicator..  (I adjusted it for zero in the middle of
>> the
>> band as I was told to do here on this reflector)..  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???   Joe
>> Thanks for your patience.......
>>
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