Fw: [Hallicrafters] SX-71 drift

[Lee Bahr]

My two SX-71s don't drift like that but I never listen on 6 meters.  They
drift for a half hour or so slowly but calm down after that.  You have
something wrong.  Could be a bad mica or silver mica, loose or bad  ground
screw or ground rivit.  (Check ground rivit resistance, if not good, drill
out the rivit and insatall a bolt, lock washer, and nut).  Maybe Deoxit
spray on tube sockets and in and around the tuning caps is in order. (Bad
tuning cap ground, or bad tuning cap rotor bearing ground, or bad tuning cap
shock grommit)?   Maybe a bad tube, maybe Deoxit is needed on band switch?
Who knows. Spray some "Circuit Chiller" on some of these items and see if
you find a critical areas that is very temperature sensitive and narrow down
the problem area.  (Of course all of the above has to do with frequency
sensitive areas of the receiver).

I purchased a new SX-96 that jumped frequency for years from time to time.
Years later when I had had enough, I  found a tubular mica cap near the
tuning cap that was making a contact with the tuning cap and caused this
jumping as it would short from time to time.  I bent the tubular cap's lead
and moved the cap slightly and I never had the problem again. (The jumping
was more like drift then a frequency jump as the shorting was very slight
and changed resistance value as it shorted).
Lee, w0vt
Houston



----- Original Message ----- 
From: "Philip B Atchley" <ko6bb at juno.com>
To: <hallicrafters at mailman.qth.net>
Sent: Sunday, August 01, 2004 11:15 AM
Subject: [Hallicrafters] SX-71 drift


> couple years back, and to all appearances is working properly in all
> aspects EXCEPT stability.
>
> For the most part, after a warm-warmupis fine for AM on all bands up
> through 10 Meters, though it needs a slight occasional tweak on 21 MHz
> up.  6 Meters tends to wander a lot when I'm listening to those
> telephones <G>.
>
> HOWEVER!  This is NOT a set one wants to use for CW or SSB work.  The
> and then switched back to receive the station had drifted right off