Elekta CTR1498 Manual - Page 4
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Print PageThis receiver is transistorized and special care should be taken when servicing. Read the following matters that demand
special attention before attempting adjustment.
1.
Adjustment requires and exact procedure and should be under taken only when necessary.
2.
An isolation transformer should be used during any dynamic service to avoid possible shock hazard.
3.
The test equipment specified or its equvalent is required to perform the alignment property. Use of equipment which does
not meet these requirements may result in improper alignment.
4.
Correct matching of the equipment is essential. Failure to use proper matching will result in responses which can not
repressent the lure operation of receiver.
5.
The AC power line voltage should be kept 215 to 225 volts 50Hz during alignment
6.
Do not attempt to connect or disconnect any wire while the receiver is in operation. Make sure the power cord is
disconnected before replacing parts in the receiver.
7.
Unless otherwise noted, do not perform arty adjustment until the receiver has been turned on for at least 10 minutes.
Note: For safety sake, the following adjustment should be conducted with the low voltage DC supply to avoid shock hazard.
TEST EQUIPMENTS
1.
AM / FM signal generator ( 4.5MHz-6.5MHz )
2.
Sweep / Marker signal operator ( 30MHz~60MHz )
3.
Sync. oscilloscope
4.
Oscilloscope ( volt sensitivity over 10mV and input impedance having 1MO, below 10PF )
5.
Probe ( Low capacitance )
6.
High impedance electronic voltmeter on VTTM ( Input impedance having 100kO / V at leasti )
7.
DC power supply ( Source such as a battery or a well regulated and isolated DC bias supply )
8.
Frequency counter.
PICTURE AND SOUND I. F. ADJUSTMENT
1. Picture I. F. Alignment
(a) Connect the signal output of sweep / marker generator to the Test Point of tuner through 1 kO resistor and 1 OOOPF capaci-
tor ( See Fig. 1 ).
(b) Connect the vertical input terminal of an sync oscilloscope in series with a 100kO resistor to TP4.
(c) Apply a + 12V DC across C120 on Main Board.
(d) Apply a + 8V DC dummy AGC bias to Pin 5 of IC101.
(e) Tune L105 and L109 to obtain a waveform as show in Fig. 2.
2. AFC OVERALL RESPONSE ALIGNMENT
(a) Act the step (a), (c) and (d) of Picture I. F. Alignment.
(b) Reconnect oscilloscope to TP5 through a 1 MO resistor.
(c) Adjust coil L110 that 38.9MHz, Marker is set at the center position as shown in Fig. 3.
SIF ALIGNMENT ( 5.5MHz )
3.
(a) Set signal generator output to 5.5MHz with AF 1 kHz, 75kHz FM modulation output level 60dB. Apply the signal to TP6
through a 1kO resistor and a 1OOOPF capacitor. As show in Fig. 4.
(b) Connect the oscilloscope input in series with a 100kO resistor to TP7
(c) Apply a + 12V DC across C120.
(d) Fine adjust L108 to abtain a maximum amplitude signal output with minimum distortion.
Note: In case of the D / K system, sound carrier frequency should be at the point of 6.5MHz and video carrier frequency at the point of
38.0MHz.