[Collins] 75A-2 question

[Gary]

Dont let the bathtub types fool you. Just got done doing up an E.H. Scott 
Navy receiver and half of the multi section bathtubs had one section that 
was no good.
My two cents.
Gary...WZ1M
----- Original Message ----- 
From: "Glen Zook" <gzook at yahoo.com>
To: <collins at mailman.qth.net>
Sent: Thursday, August 23, 2007 12:56 PM
Subject: Re: [Collins] 75A-2 question


You are thinking of the 75A-1, not the 75A-2 or 75A-3.
 The 75A-1 has all sorts of oil filled capacitors but
the later receivers have "brown beauty" paper
capacitors and not the oil filled "bathtub"
capacitors.  The "brown beauty" capacitors are just as
bad as the "black beauty" capacitors in the 75A-4 but
have brown colored bodies and not black.

All of the "brown beauty" capacitors need to be
changed out, replaced by orange drops or similar
"modern" capacitors.  It has been my experience that
none of them can even "think" of passing a "leak"
test.

While replacing the capacitors one also needs to
tighten all of the machine screws, nuts, etc., in the
radio.  All of the grounds in the receiver are made
through these and over the years these definitely work
loose.  After doing that the receiver will definitely
operate better.

When using the 75A-1, 75A-2, or 75A-3 receivers on CW
or SSB one needs to run the audio gain "wide open" and
then use the r.f. gain as the "volume control".  This
is the way to operate all superheterodyne receivers
that do not have a product detector.  The "S" meter is
not going to work but the receiver will receive the
signals MUCH better.

Glen, K9STH


--- "Dr. Gerald N. Johnson"
<geraldj at storm.weather.net> wrote:

Have the molded oil filled capacitors been replaced?
Those performing AVC bypass and time constant can
cause the AVC to be less effective leading to
distortion, but here I think its audio varying the -50
and so varying the AVC voltage.









Glen, K9STH

Website:  http://k9sth.com



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