[Elecraft] KPA100 Tool question

[Mark J. Dulcey]

Glenn Maclean wrote:
> On Tuesday Aug 13 I will have orbited the sun 50 times. In celebration for
> being 50 my family is giving me the KP100A. I have down loaded and read the
> manual in preparation of building the amp. I noticed the manual recommends a
> soldering gun to solder the power transistors. I have a good temperature
> controlled soldering station. What kind of solder gun is require? I need to
> purchase a soldering gun for other shack projects. I noticed Sears has
> 150/230, 100/140, and 100 watt solder guns. Which one would be a good all
> around gun to have and would work well for soldering the power transistors?
> Does it really matter?

You don't need a soldering gun for the power transistors. A 
temperature-controlled soldering station with an appropriate tip will do 
the job quite nicely, and is a lot easier to handle than a large, clunky 
gun. About the only common shack project I can think of that might call 
for a soldering gun is soldering PL-259 connectors; a big old soldering 
iron is even better for that, but requires more patience (they take a 
while to warm up).

What you want is a large tip - one that has lots of surface area to 
transfer heat to the transistors. On my Weller WTCPT, I used a PTB8, 
which is a fairly wide 800 degree tip; it made quick work of the big 
soldering jobs. (It did make me wish I has a second soldering station, 
though; as it was, I lost a few minutes every time I had to switch from 
the narrow 700 degree tip to the wide 800 degree tip.) I tried an even 
wider 700 degree tip first (a PTC7), but couldn't get quite enough heat 
with that. Your mileage may vary, depending on manufacturing variation 
in the irons and tips, and the solder you use. Other hams have reported 
success with a 700 degree tip.

If I were buying a soldering station now, I'd probably go for a WES50 
(which allows you to control temperature with a dial, rather than by 
changing tips) rather than the WTCPT. (They're around the same price.) 
But I already had the station from another round of building I did in 
the early 90s; at the time, it was the best available tool I could 
afford (that is to say, in the $100 class rather than the $300 and up 
class), and it is certainly Good Enough even now.

Buying the right tips can make other soldering jobs a lot easier, too. I 
find the standard Weller tip too large for some of the more crowded 
Elecraft options such as the KSB2; a narrow screwdriver tip (PTR7) or a 
long conical tip (PTS7) makes it easier to get into the narrow spaces. 
And the conical tip is really the ticket for soldering the narrowly 
spaced leads of all those SMD ICs that Elecraft kits don't have. But you 
don't want these really small tips for less crowded boards; it's hard to 
transfer enough heat with them to solder larger components or tin toroid 
leads. Weller tips are only about $5 each, so most of us can afford to 
indulge in a couple of special purpose tips.