Daewoo DTQ-26S1FC Service Manual page 8

10. PICTURE IF/AFT ADJUSTMENTS
NOTE
: THIS RECEIVER IS TRANSISTORIZED AND SPECIAL CARE MUST BE TAKEN WHEN SERVICING. READ
THE FOLLOWING (NOTES BEFORE ATTEMPTING ALIGNMENT)
Alignment requires an exacting procedure and should be undertaken only when necessary.
Isolation transformer must be used to prevent shock hazard.
The test equipment specified or its equivalent is required to perform the alignment properly. Use of equipment which
does not meet these requirements may result in improper alignment.
Accurate equipment is essential to obtain proper alignment of this receiver.
Use of excessive signal from a sweep generator can cause overloading of receiver circuit Overloading should be
avoided to obtain a true response curve. Insertion of markers from the marker generator should not cause distortion of
the response curve.
The AC Power line voltage should be kept 120 volts while alignment is being performed.
Do not attempt to disconnect any components while the receiver is in operation.
Make sure the power cord is disconnected before replacing any parts in the receiver.
TEST EQUIPMENT
Digital voltmeter
Oscilloscope
Direct/Low-capacity probe
Color-Bar/Dot/Crosshatch generator
PIF sweep marker generator
Power supply
Isolation transformer
BLOCK DIAGRAM
B+
BIAS
POWER
SUPPLY
A
(12V)
AGC
BIAS
POWER
SUPPLY
B
(4-5V)
Fig. 5 Picture IF Sweep Alignment
1) Disconnect the TUNER IF output from TP6 and connect equipment as shown above.
2) Set the sweep/marker generator for 30 Vrms.
3) Observe 1 Vp-p on scope by adjusting power supply B (4~5V).
4) Adjust PIF coil L505 for according beat signal with 45.75 MHz marker on scope (See Fig. 6).
5) Connect the DET IN to TP7.
6) Adjust AFT coil L504 for center display at 45.75 MHz on scope (See Fig. 7).
7) After completing the above steps, disconnect equipment and adjust the AGC delay circuit as explained in the General
Adjustments section of this manual.
MAIN BOARD
TP3
TP7
TP6
TP5
PIF SWEEP/MARKER GEN.
OUT
V H DETIN
National Model VP-2600A or equivalent
Tektronix Model 2215A or equivalent.
Tektronix Model P6120 or equivalent
(Accessory of oscilloscope)
Tektronix Model 146 or equivalent.
Nihon Tsushinki Model 4723 or equivalent
Academy Model 150A or equivalent
Voltage adjustable type having capacity of
at least 150 watts
OSCILLOSCOPE
Y
X
11
45.75MHz
Fig. 6 PIF Response
P
45.75MHz
Fig. 7 AFT Response Curve