[Date Prev][Date Next][Thread Prev][Thread Next] - [Date Index][Thread Index][Author Index]

Re: 5400B Intermittant control

----- Original Message -----
From: "Robert Bruninga" <bruninga@usna.edu>
To: <amsat-bb@amsat.org>
Sent: Wednesday, June 07, 2006 2:33 AM
Subject: [amsat-bb] 5400B Intermittant control

> Over the years my Yeasu 5400B rotator has been occasionally
> flakey.  Then it works again.  Today in the middle of a pass again,
> it wouldnt go left.
> After 12 years, I finally had enough and opened it up.  It appeared
> to be the relay contacts.  I cleaned them and still no go.
> Finally found the problem.  Where the relay contacts are soldered
> to the board, the relay contact pins appear to be un-tinned
> and even using the best flux I have, I could not get a good
> wet solder joint.  So I blobbed on a lot of solder and it works
> again, but if they had a run of these, I'm sure others have
> had this same problem...
> At least now I know where to kick it next time...
> Bob, WB4APR

Hi Bob, WB4APR

If you only blobbed on a lot of tin it is possible that you will
experience the same problem very soon.

The contact pins of many type of relays to be soldered on PCB's
including those used by KLM for switching polarization on 2M-22C
and 2M-14C antennas are made of a very hard alloy that is difficult
to bond with tin when using a soldering iron at a high temperature.

If you clean and polish the contact pins but the temperature of the
soldering iron is too much high you will see that immediately the
surface of the contact pin changes color from bright to blue because
of reaction with the oxigen in the air.

In this condition a good bond between the contacts pins and tin is
impossible because no alloy layer develops between metal and tin
even using a good flux cored solder wire.

The above oxidation can be prevented using the minimum possible
soldering iron temperature and a good  rosin-cored solder wire
62 Sn, 36Pb, 2 Ag wich melt at 354°F available for example from

Reading The ARRL HANDBOOK 1991 Chapter 24 page 24-6 is

73" de

i8CVS Domenico
Sent via amsat-bb@amsat.org. Opinions expressed are those of the author.
Not an AMSAT member? Join now to support the amateur satellite program!
To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org