Monday, January 05, 2015

PHILIPS 55P9271 SERVICE MODE AND POWER SUPPLY CIRCUIT

         


  SERVICE MODE AND POWER SUPPLY CIRCUIT


Service Mode Entry and Exit

Using the remote control transmitter, enter the following seven-button sequence to activate the service mode:
1. Digit 0
2. Digit 6
3. Digit 2
4. Digit 5
5. Digit 9
6. Digit 6
7. Menu

Depressing the power button on the front of the PTV will exit the service mode, save the current modification, and turn the set off. Important There are 95 registers within this system. Some of data held in these registers should not be altered and some of the other registers are factory set and unique to the unit under test. This procedure could save a significant amount of time should a mistake occur which causes an undesirable condition to the unit under test.

Description of Service Mode

The service mode is used for changing service control register values from their default values to new values; this includes all factory-preset conditions.
When entering the service mode, the tuning system will attempt to retrieve the current register values stored in the EEPROM (7304). If the EEPROM has never been programmed, default data values will be stored.
Pressing the power button on the front of the PTV while in this service mode, or setting the value of Register 00 to "00" will cause the tuning system to write all modified values to the EEPROM IC before chassis power is turned off.


SERVICE ADJUSTMENTS

PTV 830-865 Chassis GR9D Chassis
The Large Signal Panel incorporates a "hot" ground system. Always use a separate isolation transformer
when applying power to the exposed chassis.

Service Adjustment Notes

Unless otherwise specified:
1. All service adjustments are "hot" voltagewise. For maximum safety, ensure the use of properly insulated tools.
2. Many of the following adjustments are made through software intervention. The user remote control transmitter is required in order to modify register values stored within the EEPROM IC on the Main Chassis Board Assembly.
3. Grid locations (e.g., D-2) next to control reference numbers refer to PC board zone locations.

On-screen Oscillator Setup

1. Turn the set on and tune to a broadcast television signal.
2. Connect a digital voltmeter to F041 (Positive side of capacitor 2387) on the Small Signal Panel.
3. Adjust 2341 (zone E-6) to obtain a reading of 2.5Vdc (0.1V) on the meter.

Note: This adjustment may affect onscreen menu positioning or other graphics generated by the set. Refer to ”Modifying Factory Default Values“ and the contents of DAC registers 22 and 23 for vertical and horizontal positioning of the onscreen display (OSD).

RF AGC Delay (Small Signal Panels ASG059, ASG060, ASG061, ASG062, ASG063)

Tuner 1

Note: This control (3202) is located on the Small Signal Panel in zone area J-2.
1. Tune to a weak station, or loosely couple the antenna to observe a snowy picture.
2. Set the RF AGC Delay Control (3202) to its fully counterclockwise (CCW) position.
3. Slowly advance 3202 clockwise (CW) to a point slightly beyond the point of minimum snow.
Note: Do not advance the control beyond this point, as it may result in an overloaded picture on the face of the CRTs (caused by a strong signal from local station). The range of the AGC voltage supplied to pin 1 of 1900 (see F003) of the Varactor Tuner will vary from approximately 4.2Vdc (without signal) to about 1.87Vdc (RF signal of 10mV).

Tuner 2

Note: This control (3256) is located on the Small Signal Panel in zone area K-5.
1. Tune to a weak station, or loosely couple the antenna to observe a snowy picture.
2. Set the RF AGC Delay Control (3256) to its fully counterclockwise (CCW) position.
3. Slowly advance 3256 clockwise (CW) to a point slightly beyond the point of minimum snow.
Note: Do not advance the control beyond this point, as it may result in an overloaded picture on the face of the CRTs (caused by a strong signal from local station). The range of the AGC voltage supplied to pin 1 of 1900 (see F005) of the Varactor Tuner will vary from approximately 4.2Vdc (without signal) to about 1.87Vdc (RF signal of 10mV)

VCO and AFT Adjustment (Small Signal Panels ASG059, ASG060, ASG061, ASG062, ASG063)

Tuner 1

1. Cut the shield breakpoints around 7200 and the IF circuitry (see zone K-2). Remove the top cover of the shield to gain access to the internal circuitry.
2. Short circuit test points F016 and F017 (pins 1 and 2 of 7200).
3. Short circuit test point F023 (pin 13 of 7200) to ground (the shield around 7200 is a convenient ground).
4. Connect a DC voltmeter to test point F007 (pin 18 of 7200).
5. Turn the set on and record the voltage reading from test point F007 (typically 4.5 to 5.0Vdc).
6. Turn the set off and remove the short circuits from test points F016, F017, and F023.
7. Connect coincidence line test point F047 (at resistor 3361, near pin 45 of 7300) to the +5Vdc line on 1900.
8. Turn the set on and tune to a local broadcast signal.
9. Select Cable Tuning from the menu system. Select channel 36 or another high band inactive cable channel.
10. While still in the cable mode, select a local VHF broadcast channel. The tuning system will attempt to tune three times, then lock on to the FCC-assigned frequency.
11. Adjust the AFT Coil (5202) to obtain a reading of 7.1Vdc (25mVdc) at test point F004.
12. Adjust the VCO Coil (5204) to obtain the same DC voltage reading at test point F007 that was noted in step 5 of this procedure.
13. Remove the jumper from the coincidence line (F047).
14. Verify this adjustment by changing between the high band inactive cable channel and a local VHF broadcast channel (ensure that the local broadcast channel locks in quickly).

Tuner 2

1. Cut the shield breakpoints around 7201 and the IF circuitry (see zone K-5). Remove the top cover of the shield to gain access to the internal circuitry.
2. Short circuit test points F009 and F010 (pins 1 and 2 of 1204).
3. Short circuit test point F025 (pin 13 of 7201) to ground (the shield around 7201 is a convenient ground).
4. Connect a DC voltmeter to test point F008 (pin 18 of 7201).
5. Turn the set on and record the voltage reading from test point F008 (typically 4.5 to 5.0Vdc).
6. Turn the set off and remove the short circuits from test points F009, F010, and F025.
7. Connect coincidence line test point F047 (at resistor 3361, near pin 45 of 7300) to the +5Vdc line on 1901.
8. Turn the set on and tune to a local broadcast signal.
9. Select Cable Tuning from the menu system. Select channel 36 or another high band inactive cable channel.
10. While still in the cable mode, select a local VHF broadcast channel. The tuning system will attempt to tune three times, then lock on to the FCC-assigned frequency.
11. Adjust the AFT Coil (5219) to obtain a reading of 6.6Vdc ( 25mVdc) at test point F002.
12. Adjust the VCO Coil (5220) to obtain the same DC voltage reading at test point F008 that was noted in step 5 of this procedure.
13. Remove the jumper from the coincidence line (F047).
14. Verify this adjustment by changing between the high band inactive cable channel and a local VHF broadcast channel (ensure that the local broadcast channel locks in quickly).

Sound Alignment (Small Signal Panels ASG059, ASG060, ASG061, ASG062, ASG063)

Tuner 1

Note: This control (5201) is located on the Small Signal Panel in zone area J-2.
1. Select an active channel and loosely couple the antenna until noise/distortion is apparent in the output.
2. While keeping input signal weak enough to produce noise, adjust the Sound Discriminator (5201) for maximum output and minimum distortion.

Tuner 2

Note: This control (5218) is located on the Small Signal Panel in zone area K-6.
1. Select an active channel and loosely couple the antenna until noise/distortion is apparent in the output.
2. While keeping input signal weak enough to produce noise, adjust the Sound Discriminator (5218) for maximum output and minimum distortion.
130Vdc B+ Adjustment

Note: This control (7402) is located on the Large Signal Panel.
Upon replacement of the Large Signal Panel, or if a problem with the 130Vdc source is suspected, check and adjust in the following manner.
1. Connect the positive lead from a 0.1% digital voltmeter to the 130Vdc source F004 (Resistor 3453).
2. Connect the negative lead to the isolated "cold" ground.
3. Adjust 3455 (also located in the top corner of the board) to obtain a reading of 130Vdc ± 0.5Vdc.

High Voltage Adjustment

EXERCISE EXTREME CAUTION WHEN ADJUSTING HIGH VOLTAGE.
Note: The following test equipment must be used.
· High voltage probe
· Digital multimeter with 1% (or better) dc accuracy and an input impedance of 10 Megohms ± 10%

Initial settings:
· Turn the PTV on.
· Confirm that the 130V source (F004) is 130V ± 1.0V.
· Perform the 130Vdc B+ adjustment if the voltage is not within specified limits.
· Select a non-used AUX input for a black picture.
· Turn the PTV off.
With the PTV off and unplugged, connect a Fluke Model 80K-40 (or equivalent) high voltage probe as follows and adjust the high voltage.
1. Connect the ground lead to the chassis ground.
2. Connect the high voltage probe to the digital multimeter.
3. Set the digital multimeter to measure dc volts.
4. Remove one of the CRT anode connections from the high voltage splitter.

Note: Make sure that 3943 is turned fully clockwise.
5. Insert the probe tip into the open CRT anode connection of the high voltage splitter
6. Turn the set on.
7. Adjust 3943, High Voltage Adjust, on the Large Signal Panel (zone H-2) for a reading of 30kV ± 200V.
8. Turn the set off.
9. Remove the high voltage probe.
10. Reinstall the CRT anode connector.
11. Turn the set on and confirm proper operation.

High Voltage Frequency Adjustment

Note: This control (3901) is located on the Large Signal Panel in zone area H-3.
1. Turn the set off and disconnect the ac input power.
2. Disable the high voltage by shorting the collector of 7902 to ground.
3. Disable the sync input to 7950 by shorting the base of 7900 to ground.
4. Connect a frequency counter to pin 1 of 7950.
5. Turn the set on and adjust 3901 to obtain a reading of 15.75kHz on the frequency counter.
6. Turn the set off and remove the short circuits and the frequency counter.
Note: Some frequency counters may be too sensitive at one attenuation level and not sensitive enough at
another. In this case, an oscilloscope may be used. Adjust 3901 to obtain a 63.5S delay from the
leading edge of the first main pulse to the leading edge of the second main pulse.

Video Level Alignment (Small Signal Panels ASG059, ASG060, ASG061, ASG062, ASG063)

Tuner 1
Note: This control (3244) is located on the Small Signal Panel in zone area K-3.
1. Apply an NTSC color bar pattern signal to the antenna terminals.
2. Tune to the signal applied in step one.
3. Connect an oscilloscope to the emitter of 7207 (test point F001) and adjust the Video Level Control (3244)
so that the video signal observed on the oscilloscope is 2Vp-p ± 50mV.

Tuner 2
Note: This control (3265) is located on the Small Signal Panel in zone area K-5.
1. Apply an NTSC color bar pattern signal to the antenna terminals.
2. Tune to the signal applied in step one.
3. Connect an oscilloscope to the emitter of 7007 (test point F006) and adjust the Video Level Control (3265)
so that the video signal observed on the oscilloscope is 2Vp-p ± 50mV.

PROGRAMMING FACTORY DEFAULT VALUES

The chassis is controlled by an onboard microcomputer and peripheral parts which make up the tuning system. The customer picture and sound adjustments are made using either the on-set keyboard or the remote control transmitter to enter commands. There are onscreen graphics to show the menu list of adjustments. Service mode makes it possible to change the values of special memory registers in the EEPROM (7304). These registers control the customer adjustments, PIP setups, graphics intensity, and clock calibration. These
registers also make possible many other service adjustments which previously would have been controlled by conventional components mounted on the PC board.