TOSHIBA - DLP PROJECTION TV_ 46HM84_52HM84_52HMX84_ System Control Troubleshooting [Contn]

Contn:

     A look at the actual interconnection between the two circuit boards, shows us that troubleshooting can be accomplished with less difficulty by checking the PA01 side.

     The I2C bus reaches beyond the power supply circuit board to connect with the Tuner IF/IMA circuit board through the BB11 to BB10 board-to-board connections. Clock (pin 12) and data (pin 11) information, used by the Tuner IF/IMA circuits to control tuning and audio processing, is also forwarded to the Rear A/V section over the BB71 to BB70 connections (pins 19 and 20) to accommodate the video and audio switching functions.

     Taking things a step further, Figure 13 shows us the connections to main tuner H001 (pins 4 & 5), IMA block H002 (20 & 21), and sub-picture tuner HY01 (pins 10 & 11).

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     From the connections to H002, the I2C lines continue through the BB71 to BB70 connector (pins 19 & 20) to the Rear A/V circuit board. Once on the Rear A/V circuit board, Figure 14 shows us that the lines are routed to:

 #  Video switching IC QV01 [pins 45&46]

 # Audio switching IC QS01 [pins 22 & 23]

SUB-PICTURE PROCESSING

     As shown in Figure above, the I2C bus is also directed from the power supply circuit board through PV13 (pins 1 & 2) to HDMI module P202 (pins 1 & 2). I2C control of the HDMI module establishes not only functionality of the module, but also the necessary permissions required for viewing copy protected content using this all digital input.

     As shown in Figure, the I2C bus is also directed from the power supply circuit board through PV13 (pins 1 & 2) to HDMI module P202 (pins 1 & 2). I2C control of the HDMI module establishes not only functionality of the module, but also the necessary permissions required for viewing copy protected content using this all digital input.

     There are two minor exceptions to the central hub troubleshooting theory.  Operations carried out by remote control (IR) or manual keypad are transmitted to the microprocessor via direct connections to the G-Hyper/DBEP/Signal circuit boards. The block diagram of Figure 16 shows us that keypad operations are carried over PB91 (pins 5 & 6-keypad side) and PJ18 (pins 5 & 6–Signal side).

     Both signals, Key 1 and Key 2, enter IC604 (pins 6 & 7) where they are mixed and output (pin 5) as C_KEY_AB_SW (Figure 17) before entering the microprocessor at pin 78.

KEYPAD

     The keypad used in the 2004 DLP television relies on touch controls, rather than mechanical switches. Additionally, control via keypad is accomplished digitally through IC’s QA91 and QA92.

Key 1 Signals – QA91                                      Key 2 Signals – QA92

POWER (pin 22)                                                 CHANNEL DOWN (pin 22)

MENU (pin 21)                                                    CHANNEL UP (pin 21)

VOLUME DOWN (pin 19)                                  EXIT (pin 19)

VOLUME UP (pin 18)                                         TV / VIDEO (pin 18)

     Measurements can be most conveniently taken at pins 5 and 6 of PJ18 when troubleshooting suspected keypad problems. Either an oscilloscope or VOM can be used to monitor changes on the Key 1 or Key 2 lines whenever one of the front panel keys is pressed.

IR RECEIVER

     The IR receiver, KB01, is powered by the 5V-1 (Standby) supply line to pin 4 of PB22. When KB01 receives a command from the hand unit, the signal, carried between PB22 and PJ17 (G-Hyper/DBEP/Signal circuit board), travels to the system microprocessor (pin 7) via the RMT IN line at pin 3.  The system microprocessor also outputs the RMT OUT signal (pin 26) to IR transmitter DB03 (pin 1 of PB22) for IR Blaster functions.

     In addition to issuing control commands from inputs received, the system microprocessor also monitors other circuit areas of the 2004 DLP television.  Either directly or indirectly, the system microprocessor keeps a watchful eye on certain areas (Figure 20), shutting the unit down if problems are sensed.  Technical Training module DLP-04-4 Power Supply and Shutdown took great pains to identify and explain the individual protection circuits, so there is no need to repeat that information here. For the sake of review, however, we will provide a list of those circuits in this text.

• Lamp door switch.
• Color wheel exhaust fan rotation.
• Color wheel temperature sensor.
• DMD fan rotation.
• DMD temperature sensor.

Of the five circuits listed, three are directly monitored by the system microprocessor.

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