TOSHIBA - 26HL83 _ 32HL83 _ LCD TV _ POWER SUPPLY SHUTDOWN PROBLEMS

     The Power supply used in the 26HL83 LCD (Liquid Crystal Display) television is contained on two PCB assemblies. They are the Main Switching Power and Low B (DD Power module) power boards. Figure 1 points these and all other boards out, along with their physical locations in the LCD unit.

     These two supply boards are serviceable to board level only. For that reason, our service approach will address the supply voltage routing, operational levels and DC resistances to cold ground exhibited by the various sources. Using that information, troubleshooting to board level should be successful with an acceptable degree of accuracy.

PCB LAYOUT

     Shutdown on the LCD monitor/television receiver will, in most cases, be related to a thermal cause, one of the supply lines, or power supply panels themselves. It will be indicated by a blinking power LED.

• When the blinking LED symptom is observed, check the fans for rotation first. If there is no or only partial rotation of either fan, check the voltage sources for them, then change the fan if necessary. If the fan voltage sources are incorrect, suspect a problem with the Low B power supply panel.
• If nothing related to the fans or thermal shutdown is detected, since the unit is serviced to modular level, use the voltage and resistance values located in the provided charts to detect other possible modular problems.

P810 [P820B] VOLTAGES.

Contains a total of 12 pins, with the 9 and 5V2 sources occupying 8 of these pins (including source grounds). Resistance measurements to cold ground should measure in excess of 400 ohms for both sources.

P-805 is a 7-pin plug that supplies power to the scaler module. The 5V3 volt source can be found at pins 1, 2, and 3. DC resistance to cold ground should measure 1500 ohms. Pins 4, 5, 6, and 7 are ground.

P 811:  The power supply sources found here are 5.1 volts at pin 1, 32 volts at pin 6, 12 volts at pin 7, and 3.3 volts at pins 9 and 10.  Resistance to cold ground at pin 1 should measure in excess of 3K ohms, pin 6 greater than 1 Meg ohm, pin 7 greater than 20K ohms, and pin 9 greater than 5K Ohms.

P 809: is routed to the audio output PCB and contains only one source, 26 volts to operate the audio output system. Figure 9 is a detailed drawing of P809. DC resistance to cold ground should measure approximately 12K ohms.

P 816:  This plug connects the Low B sources to the scaler module. These sources consist of two 3.3 volt, one 9 volt source, and a 5 volt source. Both 3.3-volt sources should measure in excess of 700 ohms to cold ground. The 5-volt source (pin 11) should measure about 3400 ohms and the 9-volt source (pin 13) will measure about 15K ohms to cold ground.

P 818 & P819:  these plugs are used to monitor rotation and operate the fans in this unit. The 9-volt sources at pin 1 of these plugs will measure in excess of 10K ohms to cold ground.

P 817 includes the fan power source and a 5-volt source. (Figure 17) The 5-volt source should measure in excess of 3K ohms to cold ground and the fan power source should measure in excess of 87K ohms.

P 823: supplies 9, 5, and 3.3-volt sources used by the HDMI module assembley.  The 9-volt source at pin 1 and the 5-volt source at pin 3 of P823 should both measure about 450 ohms to cold ground. The 3.3-volt source will measure in excess of 7000 ohms.

PE01 is present on the Low B PCB but it is not used on this model. This plug is only used if the unit is ATSC or HD ready.