Transistors; Coils; Oscillators/Quartz - Casio PRT-40C Repair Manual

3-2 Transistors

In watches, transistors are mainly used to perform signal
amplification in the alarm (BD) and EL (LD) drive circuits.
Evaluation of their quality is performed as described below.
1) Remove the transistor to be inspected from the P.C.B.
2) Set the multimeter to the 1 KΩ or 10 KΩ range.
3) Measure the resistance between the base (B) and emit-
ter (E), and between the base (B) and collector (C). If
the transistor is acceptable, the respective resistance val-
ues will be in the range of 50-200

3-3 Coils

Coils are used to increase voltage and so forth for generat-
ing the driving voltages for the alarm and EL. Evaluation of
their quality is performed as described below.
1) Remove the coil to be inspected from the P.C.B.
2) Set the multimeter to the 1 KΩ or 10 KΩ range.
3) Measure the resistance value. If the coil is acceptable, the resistance value will be in the range of
Ω
80-150 .

3-4 Oscillators/Quartz

Oscillators/quartz produce a stable 32,768 Hz signal with
the oscillation circuit in the LSI. The most effective way
to evaluate the quality of a oscillator/quartz is to use a
dummy watch for checking oscillators/quartz. The proce-
dure for making a dummy watch is described below.
1) Have available a digital watch (preferably of the solar
battery type that does not require AC operation).
2) Disassemble the module and remove the oscillator/
quartz from the PCB ass'y.
3) Solder lead wires to the terminals to which the oscilla-
tor/quartz was soldered (XT, XTB), and reassemble
the watch with the wires extending outside the watch.
4) Attach IC clips, etc. to the terminals of the lead wires. (This completes the dummy watch.)
5) When desiring to check a oscillator/quartz, first remove that oscillator/quartz from the PCB ass'y,
and attach the IC clips of the dummy watch to its legs. If the dummy watch starts to run normally,
it means that the oscillator/quartz being checked is not defective.
Ω
. (Fig. 3-4)
— 9 —
E
C
B
NPN
E
C
C
B
Fig. 3-4
Clip
Dummy module
Fig. 3-5
E
B