-28-
DC Voltages
The voltage readings below should be used in troubleshooting the AM radio.
Q1 B 1.5V
U1 1 - 1.3V
E 1.0V
2 - 0
C 8.9V
3 - 0
4 - 0
Q2 B 1.4V
5 - 4.5V
E 0.7V
6 - 9V
C 8.9V
7 - 4.6V
8 - 1.3V
Q3 B 1.7V
E 1.0V
C 9.0V
Test Conditions
1. Volume control set to minimum.
2. Connect a jumper wire between capacitor C2 (side
that goes to the lead of the antenna coil L1) to
negative battery.
3. Battery voltage - 9.0V
4. All voltages are referenced to circuit common.
5. Voltage reading can vary +10%.
FINAL ALIGNMENT WITH NO TEST EQUIPMENT
It is best to use an earphone for this alignment
procedure.
With an alignment tool or screwdriver, turn coils L2,
T1, T2 and T3 fully counter-clockwise until they stop.
DO NOT FORCE THE COILS ANY FURTHER. Turn
each coil in about 1 1/4 to 1 1/2 turns. Set the
antenna coil about 1/8” from the end of its ferrite rod.
Refer to Figure K on page 24.
Turn the power ON and adjust the volume to a
comfortable level. Tune the dial until a weak station
is heard. If no stations are present, carefully slide the
antenna back and forth on its ferrite rod and retune
the dial if necessary. With an alignment tool or
screwdriver, adjust T1 until the station is at its
loudest. Reduce the volume control if necessary.
Adjust T2 until the station is at its loudest and reduce
the volume control if necessary. Adjust T3 until the
station is at its loudest and reduce the volume if
necessary. Retune the radio for another weak station
and repeat this procedure until there is no more
improvement noticed on the weakest possible
station. This procedure peaked the IF amplifiers to
their maximum gain.
Tune the radio until a known station around 600kHz
is found. It may be necessary to listen to the station
until their broadcast frequency is announced. If no
stations are present at the low side of the AM band,
adjust L2 until a station is heard. Once a station is
found and its broadcast frequency is known, rotate
the dial until the white pointer is aligned with that
station’s frequency marking on the dial. Adjust L2
until the station is heard. Tune the radio until a
station around 1400kHz is heard. It may be
necessary to listen to the station until their broadcast
frequency is announced. If no stations are present at
the high end of the AM band, adjust the oscillator
trimmer on the back of the gang. Once a station is
found and its broadcast frequency is known, rotate
the dial until the white pointer is aligned with that
station’s frequency marking on the dial. Adjust the
oscillator trimmer located on the back of the gang
until a station is heard. Repeat these steps until the
oscillator alignment is optimized. This procedure set
the oscillator range at 995kHz to 2055kHz.
Tune the radio for a station around 600kHz. Carefully
slide the antenna coil back and forth until the station
is at its loudest. Tune the radio for a station around
1400kHz. Adjust the antenna trimmer located on the
back of the gang (as shown in Figure 25) until the
station is at its loudest. Repeat these steps until the
antenna alignment is optimized. This procedure set
the antenna to “track” the oscillator. Once the
antenna is properly aligned, carefully apply candle
wax or glue the antenna coil to the ferrite rod to
prevent it from moving (as shown in Figure 27).
