Hafler DH-110 Instructions For Assembly And Operation Manual page 7

There are three basic rules for success in electronic kit
building:
1: Read the instructions carefully, and follow them in or-
der.
2. Make secure solder connections which are bright and
smooth.
3. Check your work carefully after each step.
The DH-110 preamplifier is a versatile component with
sophisticated circuitry which has been made remarkably
easy to build by individuals with many years of experience
in the design and engineering of the finest performing
audio kits, and in the preparation of their manuals.
Kit building should be fun, and we am certain you will
find this to be so. Fatigue increases the risk of error, so
take a break rather than push to early completion. There
are relatively few separate components in this design, to
make it easy to pack everything away, if need be.
Your work area should have good lighting and the proper
tools. The tools should include:
1. A 40 to 60 watt pencil soldering iron with a 3/16" or smal-
ler tip which reaches 700°F
2. 60/40 (60% tin) ROSIN CORE solder, l/16" diameter or
smaller.
3. A damp sponge or cloth to wipe the hot tip of the iron.
4. A wire stripping tool for removing insulation. This can
be a single-edge razor blade, but inexpensive stripping
tools are safer, faster and easier.
5. A medium-blade screwdriver (about l/4" wide).
6. Needle-nose pliers (a long, narrow tip).
7. Diagonal or side-cutting small pliers.
8. Large "gas" or "slip-joint" pliers.
9. A l/4" "Spin-tite" nut driver may be helpful, but is not
necessary.
A soldering "gun" is not recommended. The unfamiliar
user is more likely to damage the etched circuit boards
with its higher heat potential and unbalanced weight. Also,
because he may not wait long enough for it to reach operat-
ing temperature each time it is switched on, poor solder
connections are more likely. Pencil irons are much lighter
and easier to use, and there is no waiting time when solder
connections follow in sequence, as in kit building. Make
sure you have a holder for it, though, and always unplug it
when you take a break.
Proper Soldering
There are four steps to make a good solder connection:
1. Make a good mechanical connection to hold the wire in
position while heat and solder is applied.
2 . Heat the junction of the wire and lug, or eyelet, with the
bright, shiny tip of the iron.
3. After heating for a couple of seconds, apply solder to
the junction. It should melt immediately and flow
smoothly around both surfaces.
4. Allow the connection to cool undisturbed.
Remember that the connection is made by the solder,
not by mechanically attaching the wire to the terminal.
Usually the wire is looped through the lug and crimped in
place, but some prefer to just place it through the hole and
rely on the stiffness of the wire to hold it while soldering.
Eyelet connections, of course, are handled this way.
Good solder connections are essential for trouble-free,
noise-free operation. A good solder joint does not require
much solder around the conductors. Never "butter" par-
tially melted solder on the joint, as it is useless. A good
connection looks smooth and bright because the solder
flows into every crevice when the parts am hot enough.
The iron must have a bright, shiny tip to transfer heat eas-
ily to the junction. That's why the damp sponge should be
used frequently to wipe the tip, and occasionally you must
add a small amount of solder to the tip, too. If a connection
is difficult to heat, "wet" the tip with a small blob of solder
to provide a bigger contact surface to the joint. Once the
solder flows around the conductors, any movement must
be avoided for a few seconds to allow a good bond. When
cool, check the connection by wiggling the wire. If in
doubt, or if the connection is not shiny, m-heat the joint.