Panasonic PT-47WX49 47" Rear Projection Television Logo

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Question about Panasonic PT-47WX49 47" Rear Projection Television

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No power I have no power from Hot side. The power supply board is taken off from tv.When plug into a variac, power up, white wire(goes to fuse) measure normal. The black wire measured low(0.6v). TPD6 w.r.t. hot ground measured nothing.The only thing I've done is to de-solder Q801 becuase it diode tested abnormal in circuit.But tested correct out of circuit so I solder it back.What can be wrong? Thanks in advance.

Posted by peter wong on

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  • peter wong Jul 04, 2007

    Thanks for the reply.I just borrowed a service manual this afternoon so thanks for the offer.Is Q551 the horizontal output transistor? The one attached on the heatsink by the flyback?

  • peter wong Jul 09, 2007

    I reinstalled the SMPS to the tv.Checked the output transistor,it seemed ok. Did not check the rest of the components you mentioned as yet. But no B+ anywhere.Including TPD14 which should read 140v. I am thinking ,correct me if you will, that the problem might be in the hot side of the circuit.TPD6 should read 140 or so but nothing in there.

  • peter wong Jul 17, 2007

    When you say horizontal output transistor might be shorted I want to know what you mean by that and how do you test for that. I recalled that I loosed the screw on the heatsink and did a diode test on the transistor previously.I might have put it back incorrectly. "shorted"?

    I did checked the rest of the components as mentioned but find no readings.This is expected as pin14 of T801 reads no power.TPD6 is where power should goes into T801 but it reads no power.I can not check C830 as it is too big for my meter.


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Ypu will first have to check the horizontal output transistor and make sure it is not shorted. The voltage for the horizontal output transistor comes from pin14 of the SMPS transformer. Then it goes through the coil,L815, then to the diode for B+,D825. Then the B+ goes through coil L816. Be sure after D825 you check the capacitor, C830, as this is a very common fault with this set. Then the B+ flows through L817, then through two One ohm resistors, R857 and R858 to pin8 on the flyback transformer. If you get B+ on pin 8 of the Fly, and none on the horizontal output transistor, the fly is open and is bad. I have a schematic that is very close to this set but not an exact one, but most of these sets are about the same, and if you know anything about Panasonic TV sets, you should be able to repair them with a schematic from another set. BTW, this Horizontal and fly circuit is on the D board. If you wish to have a copy of the service manual for a set close to yours, I will send you a copy. If you follow these instructions, you should be able to find the fault with this TV set. If the SMPS is not working, you will not get any voltage also on the HOT. Good Luck

Posted on Jul 03, 2007

  • 5 more comments 
  • Anonymous Jul 05, 2007

    Yes it is.

  • Anonymous Jul 09, 2007

    Did you follow the directions or did you fix it , amd what was the problem?
    I bet you found something I mentioned?

  • Anonymous Jul 09, 2007

    Follow the trouble shooting to the leter, and you should find where you lose the voltage. If you do not, you will not fix the set.

  • Anonymous Jul 15, 2007

    If you do not have the 140 volts, you have an open trace or the power supply is not working.

  • Anonymous Jul 17, 2007

    Do you get any voltage on pin 8 of the flyback? No check R857, and R858, no voltage there? Check L817 and L816, no voltage there? Check for voltage on D825, no voltage there?, your power supply is not running, check all components in SMPS.

  • Anonymous Sep 07, 2007

    Check for voltage on D825 like I said before.

  • Anonymous Sep 10, 2007

    Take out the horizontal output transistor and see if the 140 volts returns. If not, replace the regulator IC in the main SMPS, and check all the small diodes as well as the zener diodes on a high scale for leakage.


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