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6-1 2
Soldering techniques
solder and a
Ordinary
soldering. I f a higher wattage-rating soldering iron is used on the etched circuit boards, excessive heat can cause
the etched circuit wiring t o separate from the base material.
6.3.
After any electrical component has been replaced the calibration of that particular circuit should be checked,
as well as the calibration of other closely related circuits.
Since the power supply affects all circuits, calibration o f the entire instrument should be checked i f work has
been done on the power supply.
For more detailed information see the interaction table (section 5.6).
6.4.
I NSTR U M E N T R EPAC K I NG
I f the instrument
i s
to be shipped to a Service Centre for service or repair, attach a tag showing owner (with
address) and the name of an individual a t your firm who can be contacted. The Service Centre needs the complete
Save and re-use the packing in which your instrument was shipped. If the original packing i s unfit for use or not
available, repack the instrument in such a way that no danger occurs during transport.
6.5.
TROUBLE-SHOOTING
6.5.1.
Introduction
The following information is provided to facilitate trouble-shooting. Information contained in other sections
of this manual should be used along with the following information t o aid in locating the defective.komponent.
An understanding of the circuit operation is helpful in locating troubles, particularly where integrated circuits
are used. Refer t o the Circuit Description section for this information.
6.5.2.
Trouble-shooting hints
If a fault appears, the following t e s t sequence can be used t o find the defective circuit part:
- Check if the settings of the controls of the oscilloscope are correct. Consult the operating instructions in
the operating manual.
- Check the equipment t o which the oscilloscope i s connected and the interconnection cables.
Check if the oscilloscope i s well-calibrated. I f not refer t o section 5 (checking and adjusting).
-
- Visually check the part of the oscilloscope in which the fault i s suspected. In this way, it is possible to find
faults such as bad soldering connections, bad interconnection plugs and wires, damaged components or
transistors and IC's that are not correctly plugged into their sockets.
- Location of the circuit part in which the fault is suspected: the symptom often indicates this part of the
circuit. I f the power supply i s defective the symptom will appear in several circuit parts.
After having carried out the previous steps, individual components in the suspected circuit parts must be
examined:
-
Transistors and diodes. Check the voltage between base and emitter (0.7 Volt approx. in conductive state)
and the voltage between collector and emitter (0,2 Volt approx. in saturation) with a voltmeter or oscilloscope.
When removed from the p.c.b. it is possible t o t e s t the transistor with an ohmmeter since the base/emitter
and base/collector junctions can be regarded as diodes. Like a normal diode, the resistance is very high in
one direction and low in the other direction. When measuring take care that the current from the ohmmeter
does not damage the component under test.
Replace the suspected component by a new one if you are sure that the circuit is not in such a condition
that the new one will be damaged.
Integrated circuits. In circuit testing cab be done with an oscilloscope or voltmeter. A good knowlegde of
-
the circuit par under test is essential. Therefore first read the circuit discription in section 2.
...
35
40
Watt pencil type soldering iron can be used for the majority of the
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