[Hallicrafters] Feedback problem with SX 99

[jeremy-ca]

Sounds like it may be a bad or missing ground connection on a component, 
especially if someone has been into it......(;

Tap as lightly as possible and see if you can localize to a section of the 
chassis.

You can also try removing the front end tubes to minimize the gain.

It might require getting into the bottom and repeating the tapping.

Carl
KM1H



----- Original Message ----- 
From: <jew123 at juno.com>
To: <hallicrafters at mailman.qth.net>
Sent: Saturday, May 31, 2008 5:05 PM
Subject: [Hallicrafters] Feedback problem with SX 99


Feedback problem with SX 99.

On bands two, three and four when I tune in a strong station the radio 
becomes micro phonic.  Since the radio sets on top of an eighteen-inch tall 
wooden speaker cabinet there is instant feedback with a low rumble.  I can 
lightly tap any of the tubes or the tuning capacitor and it is like tapping 
a microphone.

I have two sets of nos tubes except the 5Y3 and swapped out the tubes but 
that does not help.  Turning the volume or RF gain way down helps.  I can 
even tap the cabinet and it will pick it up.  Taking the radio off the 
speaker cabinet stops the feedback but the radio is still micro phonic.  I 
have recapped, put in new AC 3-wire line cord and filter caps.  I even 
repainted the cabinet restrung the dial cords.  All I have for test 
equipment is a DVM and 20k ohms per volt multi-meter.

I wonder if the radio is haunted?  Any help?

Jim Winkler
Dallas, TX


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