Hafler DH-200, Assembly And Operating Instructions Manual

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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 con­
nections are more likely. Pencil irons are much lighter and
easier to use, and there is no waiting time when solder con­
nections 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 making 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 iug, or eyelet, with the
bright, shiny tip of the iron.
3. After heating for a couple 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 connec­
tions, 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" partially
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 are hot enough. The iron must have a
bright, shiny tip to transfer heat easily 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 con­
ductors, any movement must be avoided for a few seconds to
allow a good bond. When cool, check the connection by wig­
gling the wire. If ir. doubt, or if the connection is not shiny,
re-heat the joint. Excess solder may be removed from a con­
nection by heating it and allowing the solder to flow onto the
iron, which is then wiped on the sponge.
A L L SOLDER USED MUST BE ROSIN CORE.
Never use acid core solder or any separate flux in
electronic work. Silver solder is also not suitable. If in doubt
about unmarked solder, always obtain a fresh supply of rosin
core solder. We recommend 60/40 for easiest use. Do not
confuse it with 40/60, which is harder to melt.
The general procedure is to use a hot iron for a short time
to heat a connection, then add solder with the iron still in
contact. Remove the solder once it flows, and then remove
the iron. A cooler iron applied for a longer time is more
likely to damage components, or lift the copper circuit pat­
tern from the boards. A break in the etched circuit can be
mended by simply soldering a small piece of wire across it.
Do not allow much build-up of solder on the tip of the iron,
or it may fall into adjacent circuitry.
When soldering to an eyelet on the board, insert the wire
from the components side, and apply the iron to the bottom,
leaving some bare wire exposed so that you can see that the
eyelet is then filled with solder for a secure bond. A round
wooden toothpick is suggested so that you can heat and clear
an eyelet of solder if it hinders your inserting the wire. Some
builders prefer to clear every eyelet first with a touch of the
iron and toothpick. Others connect the lead by bringing it up
to the center of the eyelet on top of the board, applying the
iron from the bottom of the board, and pushing the lead in as
the solder in the eyelet melts. If the wire has first been "tin­
ned," usually no additional solder is necessary, but it is a
good practice to push the wire through, and then back it up a
bit, to be sure solder fills the eyelet from both sides. On the
bottom of the board, make certain a bright, shiny flow is evi­
dent from the wire, across the eyelet, onto the circuit pattern
on the board. It is essential that the eyelet be fully soldered to
the .circuitry, too.
"Tinning" refers to the process of applying a light coating
of solder to the bared wire end. This keeps all the strands
secured, and also makes a good connection easier. Simply
touch the wire with the iron for a couple seconds, and apply
solder. Allow the excess to flow away onto the iron. When
properly done, the wire is uniformly bright, and no larger
than before. The hookup wire supplied with this kit does not
normally need tinning, for it is pre-tinned.
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