Heathkit IT-5283 - In Case of Difficulty

Page 34
LOGIC TRACER
When you place the prohe switch in the DC position
and the FUNCTION switch in the AUDIBLE V/ posi-
tion, an “audihle valimater” is created. This circuit
could also be called an “audible ohmmeter,” since it
will respond to either changing voltage or resistance.
When you touch the probe tip to the black test lead
alligator clip (ground), an audible tone is produced in
the speaker. As you increase the voltage or decrease
the resistance, the frequency of the tone increases. As
you
decrease
the
voltage
or
increase
the
resistance,
frequency of the tone decreases. The Signal
‘Tracer's circuitry will respond to voltages from ap-
proximately 3 volts ta +20 volts DC, and to resis-
tance from 0 1 to 5 MO.
ess
When you signal trace a logic circuit, apply a slow
square wave of 4 or 5 Hz. NOTE: Apply the probe
directly to tho gonerator's autpul to become famili
with the tone produced. Mave to each succeeding
stage throughout the logic circuitry until you no
longer hear the familiar pattern, or until you detect a
change in the frequency of the tone. While you be
come familiar with the Logic Tracer, frequent refer-
ences to ground and the supply voltage will help you
remember what to listen for with regard to “logic 1”
and “logic 0" tones.
IN CASE OF DIFFICULTY
This part of the Manual provides you with informa-
tion that will help you locate and correct difficulties
which may vccur in your Signal Tracer. This informa-
tion is divided into two sections. The first section,
“General.” contains suggestions of a general nature in
the following areas:
© Visual check and inspection.
© Precautions to observe when bench testing.
The second secti ‘roubleshooting Chart”
which contains a series of “Conditions” and “Passi
ble Causes.” Start your troubleshooting procedure by
first reading the following “General” section, Then
proceed to the appropriate “Condition” and “Possi-
ble Cause
GENERAL,
Visual Checks
1. About 90% of thekits that are returned for repair
do not function properly due to poor soldering.
Therefore, you can eliminate many troubles by a
careful inspection of connections to make sure
they are soldered as described in the “Solder-
ing” section of the “Assombly Notes." Reheat
any doubtful connections and be sure all the
wires are soldered at places where several wires
are connected. Check carefully for solder
bridges between circuit board foils.
2. Check to be sure that all transistors are in their
proper locations, and are installed correctly.
3. Check the value of each part. Be sure that the
proper part has been wired into the circuit, as
shown in the Pictorial diagrams and as called
out in the wiring instructians. It wauld he easy,
for example, to install a 2200 0 (red-rod-red)
resistor in a step that calls far a 1200 2. (brown-
red-red) resistor,
4. Recheck the wiring. Trace each lead in colored
pencil on the Pictorial as you check it. It is fre-
quently helpful to have a friend check your
work. Someone who is not familiar with the unit,
may notice something you have consistently
overlaoked.
5. Check all component lends connected to the cir-
cuit boards. Make sure the leads do not extend
too far through the circuit board and make can-
tact with other connections or parts.
6. Check all of the wires that are connected to the
circuit boord to be sure the wires do not touch
the chassis. Make sure all wires are properly
soldered.
7. Ifthe difficulty still is not cured, read the “Pre-
cautions for Hench Testing,” then refer to the
“Troubleshooting Chart.”