Universum FT-81012, Service Manual

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17
AK28 CHASSIS MANUAL ADJUSTMENTS PROCEDURE
A) PRELIMINARY
Before starting with the alignment procedure, make sure that all the potentiometers on the chassis and also screen and
focus pots are in the medium position.
B) SYSTEM VOLTAGE ADJUSTMENT
Inputs - AC power (220V 50 Hz).
- PAL B/G test pattern via RF
(PAL I test pattern for PAL I TV’s, SECAM D/K pattern, SECAM L/L´/K´ TV’s).
Outputs - Digital voltmeter to anode of D110.
Display - System voltage
Action - Apply power. Check that The stand-by led lights.
- Select TV mode and tune to the applied test pattern via local test keyboard.
Chassis should start normally.
- Adjust all analogue controls (volume, bass, treble, brightness, contrast, colour) to minimum settings.
- Adjust VR127 according to the following different types of CRT’s
SYSTEM VOLTAGE TYPE OF CRT
135V±0.5V PHILIPS A66EAK552X54
135V±0.5V PHILIPS A66EAK071X54
135V±0.5V VIDEOCOLOR A66ECY13X12
135V±0.5V PHILIPS W66ESF002X44
C) AFC ADJUSTMENT
Inputs - AC power.
- 38.9 MHz test pattern for PAL B/G, PAL-SECAM B/G or 39.5 MHz test pattern for PAL I model
(90dBmV) to Z403 SAW filter input terminals 1 and 2.
Outputs - Digital Voltmeter to AFC point (pin22 of IC401)
Display - AFC Voltage.
Action - Adjust VL401 for 2.5±0.1 Volts. TV should automatically tune to a station when
search tuning is activated.
D) FOCUS ADJUSTMENT
Inputs - AC power
- PAL B/G test pattern via RF input.
Outputs - Picture tube drive.
Display - Picture
Action - Select TV mode and tune to the signal.
- Adjust focus potentiometer (the upper pot on the rear side of the FBT transformer) for optimum
focusing.drive.
E) SCREEN ADJUSTMENT
Inputs - AC power
- PAL B/G Colour Bar test pattern via RF
Outputs - 1/100 Oscilloscope probe to RGB cathodes on CRT baseboard.
NOTE:Ground pin of probe will be connected to 1st pin (GND) of the CRT socket.
Display - RGB ratio
Action - Select PAL B/G Colour Bar pattern using the local test keyboard and the user remote control unit.
- Adjust all control functions (brightness, colour and contrast) to minimum settings.
- Measure the most sensitive cathode
- Adjust the screen potentiometer (lower pot on the rear side of FBT transformer) until cathode voltage
becomes 150V.
F) IF ADJUSTMENT FOR L’ MODE
Inputs - AC power.
- 38.9 MHz test pattern for PAL B/G, PAL-SECAM B/G or 39.5 MHz test pattern for PAL I model.
(90dBmV) to Z403 SAW filter input terminals 1 and 2.
Outputs - Digital Voltmeter to AFC point. (pin22 of IC401)
- Digital Voltmeter to AFC_L point. (pin14 of IC401)
Display - AFC Voltage.
Action - Firstly adjust VL401 for 2.5 ± 0.1 Volts. TV should automatically tune to a station.
when search tuning is activated.
- Adjust VR401 for 2.5±0.1 Volts at the AFC_L point.