Re: {Collins} 75A3

["Phil LaMarche" <plamarc1@xxxxxxxxxxx>]

Thank you and everyone, again.  I'm perhaps confused because my 75A1 sounded
so good on AM.  I upgraded to the A3 and V3.  I'll do some playing around
with headsets and another speaker I have.  You guys are wonderful.

Phil 


Philip LaMarche 
LaMarche Enterprises, Inc.
www.instantgourmetspices.com

www.w9dvm.com 
800-395-7795 pin 02 
727-944-3226 
FAX 727-937-8834 
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W9DVM 



-----Original Message-----
From: Colin Lamb [mailto:k7fm@xxxxxxxxxxxx] 
Sent: Thursday, June 25, 2009 5:51 PM
To: Phil LaMarche
Subject: RE: {Collins} 75A3

Hi Philip:

Try the Sherlock Holmes approach.  If you suspect the speaker, grab a pair
of earphones and plug in. My 75A-3 book is buried at the moment and I do not
remember if the earphone output is 4 or 600 ohms, so you will need to check
the right impedance.  Or you can connect an old stereo speaker.  It is
possible the cone on your speaker has hardened, but that usually only
happens if it has been in the sun.  Or, it could have become decentered,
which would cause a tinny sound.  But, if tuning off to the side helps, that
may be the nature of the filter in the radio.  

If the earphones and speaker sound the same, then it is coming from the
radio.  It is possible the electrolytic bypass for the cathode is dry, which
would reduce bass response - but again that would not be solved by tuning
off frequency.  

Old mechanical filters fail, which can give you a tinny sound, so that
cannot be discounted.  Some hams have gone to a wider filter.  You might do
a Google search, after removing other possibilities, and see what others
have done to enhance the audio.  You will not get high fidelity with the 6
kc filter, listening to am.  

73,  Colin  K7FM