3
( )
Insert Molex receptacle J4 into the PC board making sure to orient it
as shown in the component layout drawing. The notches on the connector
must point toward the edge of the PC board as shown in the component
layout drawing. Solder.
NOTE: MOS integrated circuits are susceptible to damage by static
electricity. Although some degree of protection is provided internally within the
integrated circuits, their cost demands the utmost in care. Before opening and/or
installing any MOS integrated circuits you should ground your body and all
metallic tools coming into contact with the leads, thru a 1 M ohm 1/4 watt
resistor (supplied with the kit). The ground must be an "earth" ground such as a
water pipe, and not the circuit board ground. As for the connection to your body,
attach a clip lead to your watch or metal ID bracelet. Make absolutely sure you
have the 1 Meg ohm resistor connected between you and the "earth" ground,
otherwise you will be creating a dangerous shock hazard. Avoid touching the leads
of the integrated circuits any more than necessary when installing them, even if
you are grounded. On those MOS IC's being soldered in place the tip of the
soldering iron should be grounded as well (separately from your body ground)
either with or without a 1 Meg ohm resistor. Most soldering irons having a three
prong line cord plug already have a grounded tip. Static electricity should be an
important consideration in cold, dry environments. It is less of a problem when
it is warm and humid.
( )
Install MOS integrated circuits ICI and IC2 following the precautions
given in the preceding section. As each is installed, make sure it is
down firmly against the board before soldering all of its leads. Be
very careful to install each in its correct position. Do not bend the
leads on the back side of the board. Doing so makes it very difficult
to remove the integrated circuits should replacement ever be necessary.
The "dot" on the end of the package is used for orientation purposes
and must match with that shown on the component layout drawing for each
of the IC's.
( )
Working from the "TOP" side of the circuit board, fill in all of the
feedthru's with molten solder. The feed-thru's are those unused holes
on the board whose internal plating connects the "TOP" and "BOTTOM"
circuit connections. Filling these feed-thru's with molten solder
guarantees the integrity of the connections and increases the current
handling capability.
( )
Now that all of the components have been installed on the board, double
check to make sure all have been installed correctly in their proper
location.
( )
Check very carefully to make sure that all connections have been
soldered. It is very easy to miss some connections when soldering which
can really cause some hard to find problems later during check out.
Also look for solder "bridges" and "cold" solder joints which are
another common problem.
This completes the assembly of the PR-40A circuit board.