[Hallicrafters] SX-101 Mk III Overload / Desense

[Andrew, Jim - BD]

Hi Mike, 

Thanks much for the note and the thought on this. 

My signal generator - surprise - doesn't go that low, hence the ear tune after the earlier stages were done by the book. I note the BFO generates a signal near 50.5 kHz and presumably could be tuned there. Wonder if folks have had luck taking the BFO output and using that to align the 50.5 IF. 

Jim


-----Original Message-----
From: hallicrafters-bounces at mailman.qth.net [mailto:hallicrafters-bounces at mailman.qth.net] On Behalf Of Mike Everette
Sent: Thursday, December 02, 2010 9:52 PM
To: Andrew, Jim - BD; hallicrafters at mailman.qth.net
Subject: Re: [Hallicrafters] SX-101 Mk III Overload / Desense

Jim,

I think the operative phrase -- the key to the issue is "I have peaked the 50.5 
kc IF by ear."

Unfortunately that is a No-No.  You have probably screwed things up royally, 
such that you have "lost a sideband" by getting the passband out of whack.  


When working on the Halli "selectable sideband" receivers, or the Hammarlund 
HQ-170/180 as well, one keeps one's hands off the low IF adjustments unless one 
has the test gear -- and the skill -- to do the job right.

These circuits typically do not require realignment unless there have been 
really major issues with them.  Normal recapping generally does not result in 
major issues.

Your best bet is to find someone with a signal generator, and a frequency 
counter, capable of giving an accurate signal to align the IF.  Either get the 
person to help you, or borrow the equipment and follow the procedure in the 
manual, exactly.  It really does require precision.  If you haven't done this 
before it would definitely be best to get some help in so doing.

I have learned this from experience.  Experience is a harsh taskmaster.

73

Mike
W4DSE


      
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