[Collins] 75A-3

[Jim]

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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