[Elecraft] K3: PTT IN problem - cause found...Joe picked it...

[Ron D'Eau Claire]

A two-terminal SMD is very easy to replace. Find a small, thin tool (e.g.
tiny screwdriver, tip of a knife blade or even a toothpick) and place it
where the SMD body touches the board and lift up on the SMD while heating
one end with your soldering iron. It will tilt up, held by the solder at the
other end. Now touch the other end with your iron while holding the part
with small needle nose pliers or tweezers to free it. 

Clean any excess solder off of the pads and leave a small drop of fresh
solder on each pad. 

Set the new part in place and hold it in place with the little tool you used
to pry the old part off with earlier. Touch one end, then the other with
your soldering iron to "sweat-solder" the part in place. Optionally, you can
clean off the pads entirely and have a tiny drop of solder on the tip of
your iron that will flow onto the solder pad when you touch each end. That's
a little trickier to do at first. Most people tend to have too big of a drop
of solder on the iron. If your first just make a "bump" of fresh solder on
each pad and wipe your iron before touching it to the joint, you won't have
excess solder. 

All done!

The biggest mistake most O.T.s make is trying to solder the new part in
place by putting the iron on the joint and feeding in rosin-core solder like
we did when mounting big leaded parts on tube sockets or terminal strips!
That is not necessary. The "sweat-soldered" joint is perfect. 

Another mistake is to hold the iron in mid-air the way we wielded the
100-watt soldering behemoths of old. Even if you are a rock-solid
20-something who does brain surgery on the side, arrange your work to brace
your arms or hands against something solid so you can easily hold the tools
exactly where you want them. 

73,

Ron AC7AC   

-----Original Message-----
From: elecraft-bounces at mailman.qth.net
[mailto:elecraft-bounces at mailman.qth.net] On Behalf Of VK7JB
Sent: Thursday, April 12, 2012 5:29 AM
To: elecraft at mailman.qth.net
Subject: Re: [Elecraft] K3: PTT IN problem - cause found...Joe picked it...

Thanks Joe - you picked it in one!   No voltage on PTT IN.  RFC1 on the RF
board has failed open (9 M Ohm on my meter) and bypassing it restores the
PTT IN 5V line voltage and function, as you'd expect.

It's a surface mount component on the bottom of the RF board, for those who
might need to know in the future.

Next challenge is to replace it - I'm not very experience with SMC building,
but I'll give it a go.  Or, would there be any problem replacing it with a
standard RFC of the same value if I can configure it to fit?

73,

John
VK7B