[Hallicrafters] RE: GB> SX-101A

[Carpenter, Robert E CIV]

I would suspect filter capacitors first then the by-pass caps next.  The
best way to troubleshoot motor-boating problems is to have on hand a few
caps of various values used to bridge, (parallel) suspected caps.  Pick
a bridge cap value that is near to the value of the suspected cap.  I
can say that I've used a 0.1 ufd at 600 volts to bridge the filter caps
and even though it didn't clear the motor-boating completely, it made
enough change to determine which cap was bad.   Good luck and let us
know how you make out.

73 de Bob, N3LKL 

-----Original Message-----
From: owner-glowbugs at piobaire.mines.uidaho.edu
[mailto:owner-glowbugs at piobaire.mines.uidaho.edu] On Behalf Of Langston,
Mike
Sent: Wednesday, May 30, 2007 4:36 PM
To: Hallicrafters at mailman.qth.net
Cc: glowbugs at piobaire.mines.uidaho.edu
Subject: GB> SX-101A

Mine was working just fine. It had been a couple of months since I last
used it so I fired it up over the Memorial weekend. Now it has this
"problem". 

 

It's going to be hard to describe. It is like a steady pulsing
interruption to the signal, barely discernable on SSB except with very
slow talkers. But with a steady carrier or by turning on the calibrator
it is very noticeable. The interruption is very short (much shorter than
a "dit") and the rate is about 3-4 per second. 

 

The sensitivity, selectivity, AVC, calibrator, and noise limiter are all
normal.

 

I've heard the term "motor-boating" used before but I'm not sure what
circuit is susceptible to it or what it sounds like. The reason I
mention it is that with a steady carrier, it sounds like an outboard
motor idling. There is no noticeable effect on s-meter action.

 

I'm looking for suggestions before I jerk it out of the case to begin
troubleshooting.

 

Thanks for any help.

 

Mike KL7CD

Dallas-Ft. Worth