Service Manuals, User Guides, Schematic Diagrams or docs for : panasonic LCD TX-26LMD70 TX-26LMD70

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TX-26LMD70


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                     For Authorised Service Agents Only
                                                                               Ref No:     122923101365258BR

                                                                              Date:            01/10/09
   TECHNICAL INFORMATION                                                                Created by
                                                                                Panasonic UK - Service Group

Document Category:           Knowledge Base


Subject:                     TV switches on with green led blinking then goes off.

Model(s) Affected:           TX-26LMD70       TX-32LMD70

Problem / Issue              TV switches on with green led blinking , picture appears for split second then set
                             turns off and the cycle repeats.

Solution:                    This is caused by a faulty P pcb. Due to R850 (820K Ohm) gone high in value




      Hints:

   When faulty: - the 24V line dips when the backlights come on and at this moment the TV will
   switch off and on again!

   This 24 v goes to the AP pcb and produces a reset signal> 24vDET> which resets the DG pcb.

   The drop in 24v rail was causing continuous DG pcb resets at power up and hence the
   Continuous power up/down cycle
   The regulation pin 11 if ic802 is being driven abnormally by a faulty R850 (820K)

   R850 provides bias to turn on Q807 and hold off Q808




            Confidential                             Page 1                  122923101365258BRREV1
If Q808 is not off it can corrupt the regulation line to ic802
=====================================

SERVICE HINTS:

The PSU reverse side can be worked on by using the lead: RFKZ0171

to connect P5 > AP2 and leaving the inverter leads connected as attached
=====================================

BOOT UP PROCESS OF THESE SETS:

At switch on > the DG pcb gets 5v stby (FROM ic3805 on AP PCB), boots up and produces
the TUNER SUB control line (3v) > pin 14, P5 connector to turn on psu IC802, and also to turn
on the AP pcb sub supplies below>

 SUB9v (from Q3810)
Q3813 > switched 24V
sub5v from Q3803

after above rails come up from Ap pcb the TUNER MAIN ON line goes high (from DG pcb > AP4
pin 18) to turn on remaining rails for set operation>

16v > ic3802 (ap pcb)
MAIN9V > q3811 (AP PCB)


Finally the DG pcb sends out PANEL ON control signal (AP 4 pin 9) to turn on panel 12v from
IC3801 > used for LCD video drive pcb
failure of the above DG pcb control signals to come up indicate a possible Dg pcb fault

Check AP pcb operation as per above boot up process.

Sometimes AP pcb may have failed regulators causing boot up problems




       Confidential                           Page 2             122923101365258BRREV1



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