AMSTRAD CB-901 SERVICE MANUAL
Contents
1. ponsa 58565 ect fies Hines og 256289 ou 2516080 1174 oT nis AYBS eos u tawo tatoo u3 taio D nene 5 11056705 PCMAQO2F AMSTRAD 621901 44 QD a0 are aw Powte VOLTS at TAGLI CAROLE 7 PORIA SUPPLE oF Mason 1082. AMSTRAD CB 901 SERVICE MANUAL www meetthebreakers co uk Transmitter Alignment CRYSTAL OSCILLATOR ALIGNMENT 10 240MHz Connect Frequency counter to Pin 11 of U1 through 100pF Ceramic Capacitor Adjust L2 for 10 240000MHz 50Hz VCO ALIGNMENT Set radio to channel 1 Measure voltage between R6 C9 junction and ground Adjust T1 to read 2 0V Set radio to Transmit Adjust CT1 to read 2 0V Set radio to channel 40 TX Check for voltage of 4 to 5V RF POWER ALIGNMENT Set radio to channel 20 Set 10dB attenuator switch at IN position Preset cores of T2 T3 and T4 3 turns inside from top Preset core of L4 1 turn counter clockwise from the bottom Preset L8 1 turn outside the top Set unit to Transmit Adjust T2 T3 T4 L4 and L8 for maximum output on oscilloscope and wattmeter RF POWER CHECK Set radio to channel 20 Set radio to transmit Check power output is between 3 7W and 4 0W Check that current drain is less than 1 6A Put attenuation switch to out position Check output power is between 0 2W and 0 4W Check that current drain is less than 0 7A Repeat the steps above for channel 1 and channel 40 FREQUENCY ALIGNMENT Set radio to channel 20 Set unit to Transmit Adjust L2 to obtain 27 79125MHz 300hz Check channel 1 for 27 60125MHz 300hz Check channel 40 for 27 99125Mhz 300hz MODULATION ALIGNMENT Set radio to channel 20 Set radio to Transmit Apply 3mV 1 25kHz audio input to mic
3. socket Adjust RV3 for deviation for between 0 8kHz and 1 0 2 RF METER ALIGNMENT Set 10dB switch out Set unit to Transmit Adjust RV1 to light red LED number 5 Set 10dB switch in All LEDS should now be lit Receiver Alignment RECEIVER SENSIVITY ALIGNMENT Set radio to channel 20 Connect voltmeter to RV2 Inject signal of 27 79125MHz with RF input signal of 4uV 1kHz 1 5kHz deviation Adjust T5 T6 T7 T8 T9 T10 for maximum voltage reading Reduce RF input signal to zero Adjust T11 for max noise output at speaker Apply 1 RF input signal re adjust T11 for max audio output and minimum distortion SQUELCH ALIGNMENT Set squelch control to maximum clockwise Set RF gain control to maximum clockwise Apply 7uV RF signal with 1kHz 1 5kHz deviation Adjust RV5 so that output from speaker just disappears S METER ALIGNMENT Set radio to channel 20 Apply 100uV from signal generator Adjust RV2 so that green LED lights PCLDOOZF 010 010 000 Ja PCMCOOIF par a aur rer ary e 2522 9 4 m e has How naom raw CB901 CIRCUIT DIAGRAM 92 Os t werommanion
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