Instruction manual

3. Make sure that all of the parts are placed in
their correct positions. Check if the IC, diode
and lytic orientations are correct.
4.
Use a 2” wire to short capacitor C2 (see Figure M).
Turn the volume control up halfway:
a)
Short by wire, the speaker terminals several
times. If you don’t hear tapping from the
speaker, check the speaker, battery, battery
holder, capacitor C6 and the switch.
b) Short by wire, pins 4 and 5 of IC2 several
times. If you don’t hear tapping from the
speaker, check the wires from the PC board to
the speaker and capacitor C7.
c) Short pins 2 and 3 of IC2 several times. If
you don’t hear tapping from the speaker,
check IC2 and capacitor C8.
d)
Short pins 1 and 3 of IC1 several times. If you
don’t hear tapping from the speaker, check
capacitors C3, C4 and C5 and resistor R3.
e) Short pins 2 and 3 of IC1 several times. If
you don’t hear tapping from the speaker,
check IC1, R1, R2, R4, R5, D1, D2 and C1.
Turn OFF power. Remove the short wire
from C2.
f)
Check the antenna coils L1 and L2 and
capacitor C2. If you have an ohmmeter,
measure the resistance on the pads of
capacitor C2 (see Figure N). The
resistance should be approximately 11Ω. If
the resistance is infinity, check the antenna
coils L1 and L2. If the resistance is around
“0”, check capacitor C2.
5. The DC voltage readings below should be used
for test conditions: Volume set to minimum,
battery voltage = 9V; all voltages are referenced
to the circuit common. Voltage readings can
vary +
10%.
Note: C2 should be shorted.
(IC2) 1 - 1.32V (IC1) 1 (output) - .830V
2 - 8mV 2 (input) - .810V
3 - 0 3 (GND) - 0
4 - 0
5 - 4.35V
6 - 9V Anode of D1 - 1.33V
7 - 4.55V Anode of D2 - .720
8 - 1.33V
-9-
Figure M
C2
Ω
Figure N