Specifications

Introduction
Assembly of your signal tracer will prove to be an exciting project and give
much satisfaction and personal achievement. If you have experience in
soldering and wiring techniques, you should have no problems. For the
beginner, care must be given to identifying the proper components and
good soldering habits. Above all, take your time and follow the easy step-
by-step instructions. Remember, an ounce of prevention is worth a pound
of cure. Avoid making mistakes and no problems will occur.
Parts Verification
Before beginning the assembly process, familiarize yourself with the
components and this instruction book. Verify that all parts are present.
This is best done by checking off each item against the parts list.
Resistors are identified by their color code as shown in the assembly
instructions.
Soldering
The most important factor in assembling your signal tracer is good
soldering techniques. Using the proper soldering iron is of prime
importance. A small pencil type iron of 25-40 watts is recommended. The
tip of the iron should be the flipplet point type and at all times kept clean
and well tinned. Many areas on the main 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 simultaneously
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 blob the solder over the lead because this could
result in a cold solder joint.
Assemble Components
In all of the following assembly steps, the components must be installed
on the top side of the 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. Clip excessive leads with diagonal cutters. Then, place a
check mark in the box next to the step indicating that the step is complete.
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Troubleshooting Guide
The following guide should help in solving any problems encountered with
your signal tracer. First, check your unit for soldering or wiring errors.
Next, check the voltage at the emitter of transistor Q1. It should measure
between 4.5 to 5.5 volts. If you still have a problem, refer to the following
sections for help.
I. LED does not light:
A) Be sure the red clip is connected to a positive voltage between 5 to
40 volts, and the black clip is connected to ground.
B) Check the LED, it may be in backwards or open.
C) If 4.5 to 5.5 volts is present at the emitter of transistor Q1, proceed
to II.
D) Check the zener diode D1, transistor Q1, and capacitors C5 and C6
for backwards installation.
E) Make sure R9 and R10 are not interchanged.
II. Weak or no sound in earphones with green clip connected
to probe tip, and the LED is on:
A) Check to see if the IC is in backwards.
B) Must determine if the oscillator or amplifier is at fault. If an
oscilloscope is available, look at the output of the op-amp (pin 1).
There should be 3 to 5V of a 1kHz squarewave.
If no scope is available, put the switch to tip receive position and
remove the green alligator clip from the tip. Touch the tip with your
finger. The earphone will buzz with 60Hz response when the gain
control is fully clockwise and the amplifier is operational.
C) If the oscillator is at fault:
Check the LM-358 op-amp (pins 1, 2, 3, 4, and 8), resistors R1 to
R6 and capacitors C1 and C2 for soldering or wiring errors.
Replace the LM-358 op-amp if there are no solder or wiring errors.
D) If the amplifier is at fault:
Check the LM-358 (pins 4 to 8), trim pot R11, resistors R7, R8, and
capacitors C3 and C4, for soldering or wiring errors.
Replace the LM-358 op-amp if there are no solder or wiring errors.
E) Check switch S1.