Elenco Electronics XK-550K, Assembly And Instruction Manual

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CONSTRUCTION

Introduction

Assembly of your XK-550 Digital/Analog Trainer Kit will prove to be an exciting project and give you much satisfaction and personal
achievement. If you have experience in soldering and wiring techniques, then you should have no problem with the assembly of this kit.
Care must be given to identifying the proper components and in good soldering habits. Above all, take your time and follow these easy
step-by-step instructions. Remember, “An ounce of prevention is worth a pound of cure”. Avoid making mistakes and no problems will
occur.

CAUTION: WEAR SAFETY GLASSES WHEN ASSEMBLING THIS KIT.

Assemble Components

In all of the following assembly steps, the components must be installed on the top side of the PC board unless otherwise indicated. The
top legend shows where each component goes. The leads pass through the corresponding holes and the board is turned to solder the
component leads on the foil side. Solder immediately unless the pad is adjacent to another hole which will interfere with the placement
of the other component. Cut excessive leads with a diagonal cutter. Then, place a check mark in the box provided next to each step to
indicate that the step is completed. Be sure to save the extra leads for use as jumper wires if needed.

Soldering

The most important factor in assembling your digital / analog trainer is good soldering techniques. Using the proper soldering iron is of
prime importance. A small pencil type soldering iron of 25 - 40 watts is recommended. The tip of the iron must be kept clean at all
times and well tinned. Many areas on the PC board are close together and care must be given not to form solder shorts. Size and
care of the tip will eliminate problems.

For a good soldering job, the areas being soldered must be heated sufficiently so that the solder flows freely. Apply the solder simulta-
neously to the component lead and the component pad on the PC board so that good solder flow will occur. Be sure that the lead
extends through the solder smoothly indicating a good solder joint. Use only rosin core solder of 60/40 alloy.
DO NOT USE ACID CORE SOLDER! Do not blob the solder over the lead because this can result in a cold solder joint.

1.

Solder all components from
the copper foil side only.
Push the soldering iron tip
against both the lead and the
circuit board foil.

Component Lead

Soldering Iron

Circuit Board

Foil

2.

First apply a small amount of
solder to the iron tip. This
allows the heat to leave the
iron and onto the foil.
Immediately apply solder to
the opposite side of the con-
nection, away from the iron.
Allow the heated component
and the circuit foil to melt the
solder.

Solder

Soldering Iron

Foil

Example 1

Poor solder connections occur
when the lead is not heated
sufficiently. The solder will not
flow onto the lead as shown. To
correct. reheat the connection
and, if necessary, apply a small
amount of additional solder to
obtain a good connection.

Solder does not flow onto the
lead. A hard rosin bead sur-
rounds and insulates the con-
nection.

Poor solder
connection

Mount Part

Soldering iron posi-
tioned incorrectly.

Example 2

A solder bridge occurs when
solder runs between circuit
paths and creates a short cir-
cuit. This is usually caused by
using too much solder. To cor-
rect this, simply drag your sol-
dering iron across the solder
bridge as shown.

4.

Here is what a good solder
connection looks like. Cut
off excess leads.

3.

Allow the solder to flow
around the connection.
Then, remove the solder and
the iron and let the connec-
tion cool. The solder should
have flowed smoothly and
not lump around the wire
lead.

Solder

Soldering Iron

Foil

Bend Leads to Hold Part

Solder and Cut Off Leads

Foil Side

Rx - 100

Ω

5% 1/4W Resistor

(brown-black-brown-gold)

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