Elenco Electronics AM-550TK Instruction Manual download pdf (Page 30)

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DC Voltages

The voltage readings below should be used in troubleshooting the AM radio.

Q1 B 1.5V Q5 B 8.3V

E 1.0V E 9.0V

C 8.9V C 5.8V

Q2 B 1.4V Q6 B 5.8V

E 0.7V E 5.2V

C 8.9V C 9.0V

Q3 B 1.7V Q7 B 4.6V

E 1.0V E 5.2V

C 9.0V C 0.0V

Q4 B 5.7V

E 5.2V

C 8.3V

Test Conditions

1. Volume control set to minimum.

2. Connect a jumper wire between capacitor C2 (side

that goes to red lead of coil L1) to negative battery.

3. Battery voltage - 9.0V

4. All voltages are referenced to circuit common.

5. Voltage reading can vary +

10%.

AM ALIGNMENT WITH NO TEST EQUIPMENT

It is best to use an earphone for this alignment

procedure. Rotate the tuning knob fully counter-

clockwise and place the label on the knob with the

white arrow pointing at the 540kHz marking.

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 J 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 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 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 24).

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Elenco Electronics AM-550TK Instruction Manual Page 30

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