{Collins} Re: 75A2



FYI, Collins engineers published a series of design changes to the 75A2 in
QST in the 50's, I don't remember the issue, that outlined many changes to
the circuit and tube count, like changing the mixers to 6ab7's.... The
changes were later shipped in the new production models of the A2.  Looks
like you might have a newer A2 with the older manual.

Ciao, k0eoo 

-----Original Message-----
From: collins-bounce@xxxxxxxxxxxxxxxxxxxxx
[mailto:collins-bounce@xxxxxxxxxxxxxxxxxxxxx]On Behalf Of GARY ELLIOT
Sent: Wednesday, July 21, 2004 9:28 PM
To: collins@xxxxxxxxxxxxx
Subject: {Collins} 75A2


As I continue with my restoration of a 75A2 I have run into some
discrepancies, namely the reproduction manual that came with the receiver
has the 1St & 2ND mixers listed as 6BA7's.  Yet the chassis is stamped V2 &
V4 as 6BE6's.  The schematic shows the output of the 70E12 PTO to pin 2 of
the 6BA7.  Yet my radio has the output of the PTO connected to Pin 1.  Also
there are some different resistor values associated with this scoket then is
shown on the schematic.
Was there a service bulletin or any mods that may have appeared in Ham
Magazines changing the mixers in the 75A2 ?  The schematic I am working off
is dated April 1954.

Couple other questions regarding the 75A2, does any one make the Kilocycles
(round dial) reproductions ?

I also need the PTO coupling which is apparently .25 inch on one end and
3/16 or some other close dia on the PTO shaft, not having a micrometer I
can't measure the actual shaft size on the 70E-12 PTO.

The difference in the mixers has me rather confused and appreciate any
comments from anyone familiar with this receiver, Thanks

73 Gary


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Nets: Tues: 3.805 Mc-2000 Central / Thur: 3.875 Mc-2000 Central
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1st Wed (of the month) AM Net 3.880 Mc-2000 local (ET, CT, MT, PT)
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