[WRL] Possible problem source

[john.brewer at us.schneider-electric.com]

Hi Glen,

This seems to be largely a problem with miniature tubes (or quite possibly, their
sockets). I've rarely seen this in older Octal - type tubes, but I do see this
quite often in Drake gear. I suspect it's a combination of inexpensive sockets
(phenolic in both Drake and Heath) and  the smaller pins with less contact
area, and different pin finish.

That's my guess anyway! I do know, many Drake pieces that cross my
bench, come back to life with wiggling the tubes in their sockets.

John K5MO




                                                                                               
             Glen Zook                                                                         
             <gzook at yahoo.com>                                                                 
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                                                                                       Subject 
             02/17/2005 12:25 AM               [WRL] Possible problem source                   
                                                                                               
                                                                                               
                                                                                               
                                                                                               
                                                                                               
                                                                                               




Tonight my Heath SB-110A 6-meter rig developed a
couple of problems.  First of all, I tightened all of
the screws that hold the printed circuit boards to the
chassis.  Then I took a paint brush and cleaned
everything on top of the chassis.  Finally, before
disconnecting the rig and taking it to the service
bench I started unplugging and then plugging in again
the tubes in the circuit "area" that the problem was
occurring (the push to talk circuit was "hanging" for
several seconds after releasing the microphone).

When I removed the 6AZ8 that controls the relay the
unit returned to receive.  Of course I had to return
the tube to its socket before the unit would operate
again.  I "wiggled" the tube, I removed and replaced
it, and so on.

Finally, I actually removed the tube, removed the tube
shield, and took a good look at it.  Frankly, the tube
pins had corroded over the years and just were not
making a good connection to the socket.

Since I keep a jar of Goddard's "Silver Dip" around to
clean various items (like coax connectors) I "dipped"
the tube pins in the solution.  After a good rinse at
the sink and a good dry with a towel I replaced the
tube.  Problem solved!

I then checked the other tubes and all of their pins
were showing various signs of corrosion.  Thus, I
cleaned them one-at-a-time.  Of course most of the
tubes in the SB-110A are actually original, and since
the unit works perfectly, I haven't replaced a tube in
years.

I now plan on cleaning the tube pins, along with
tightening all of the hardware that holds everything
in place on any boat anchor that I work on that had
intermittent problems.  In fact, I really think that
it would be a good idea to actually clean all of the
tube pins whenever I work on a unit for someone else.

Corrosion on tube pins is not something that you
immediately think about when troubleshooting a "boat
anchor".  But, it certainly can be a source of
problems.  Often we clean the sockets as well as
switches, potentiometers, and so forth.  However, how
often do we think of cleaning the pins on the tubes?!!

Glen, K9STH

=====
Glen, K9STH

Web sites

http://home.comcast.net/~k9sth
http://home.comcast.net/~zcomco



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