[Collins] Mech filters in 75A3 - mechanical Filters

[Al Parker]

Hi all,
    I discovered today that I have an original Collins mod that shows this
2-tube plug-in.  I think it's titled "Filter for 75A1" or similar (don't hv
it in front of me now).
    If there's interest, I'll scan & send to anyone, or get it on my
website if too many requests.
73,
Al, W8UT
New Bern, NC
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----- Original Message -----
From: "Rodney Bunt" <rodney_bunt@yahoo.com>
> The 75A-3 was a 75A-2 with mechanical filters, it came out in abouot
1954, there was a retrofit to  the 75A-2 called the 75A-2a it was the same
performance as the 75A-3.
>
> There was story on how to add mechanical filters in QST in the 1954 year,
can't remember which one (I won a bunch of QST on eBay and am in the
process of reading them all, I haven't read Oct, Nov,  Dec 1954 so it is
earlier).
>
> It is an interesting mod, in that that it was a plug and play mod.
>
> The First IF tube was removed (unplugged) and a box with an Octal plug on
the bottom inserted, and it had two minature tubes and a crystal filter
installed.
> If you wanted to go back to 6kHz just plug in the Old Tube.

> > --- "Guy Olinger, K2AV" <k2av@contesting.com> wrote:
> > I note that some 75A3's have a pair of mechanical filters selectable
> > from a lever behind one of the front panel knobs.
> >
> > Where can I find out the filters that are used for this setup. Was
> > this a factory mod or what?
> > Guy, K2AV