Question about Panasonic TH-42PA20U/P 42 in. Plasma EDTV

3 Answers

Blinking power light. same even after unplugging and plugging ac power. relays click as if unit trying to come on, but at 2nd relay click, power light flashes.

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  • 12 more comments 
  • jesunkel Oct 09, 2010

    please send the link to service manual.

    Also, BTW, this model does not support HDMI connex.

    Thanx...

  • jesunkel Oct 09, 2010

    The light blinks 11 times, then is on for about 2 seconds, then blinks 11 times again.

  • jesunkel Oct 09, 2010

    No fan in this unit. P10 has no cable connected. FAN SOS appears to be a pass-thru to D PCB and into IC 9709.

    Also surprisingly little dust inside unit; vent ports not congested.

  • jesunkel Oct 09, 2010

    Additionally, the manual I downloaded states that a fan problem would be 6 flashes and only gives data for up to 9 flashes. It does not have an entry in the "flash" table for 11 flashes.

  • jesunkel Oct 10, 2010

    No visible defects on the caps.

    Measured P2 and Vsus = 5.4v
    Measured P7 and 12v = 0
    measured P23 and DR15V = 0

  • jesunkel Oct 14, 2010

    Sent readings, what next?

  • jesunkel Oct 16, 2010

    They guy I was working with no longer replies, I have been charged, and problem did not get fixed.

    What gives?

  • jesunkel Oct 16, 2010

    Hmmmmm, as I explained to the previous chap, there is no fan in this unit. The connector on the P board (P10) has nothing connected to it.

    I downloaded a Panasonic manual from a site recommended previously and in its error blink table, it indicates that 6 blinks would be the fan, and it does not have any entries in the error table greater than 9 blinks.

    Upon measuring some of the voltages at the output connectors for the P board there is for instance no 5v or 12v or 15v out.

  • jesunkel Oct 20, 2010

    Number of blinks depends on whether you are count the "off" period or the "on" period. If you count the off period, 11 blinks. If you count the "on" period, 12 blinks.


    There is, btw no fan in this unit.

  • jesunkel Oct 21, 2010

    Looks like 12.

  • jesunkel Oct 21, 2010

    No physical defects to any caps that I can see.

  • jesunkel Oct 22, 2010

    Sorry, no capacitance measurement capabilities on DMM.

  • jesunkel Nov 17, 2010

    Replaced PS board, still same symptom. What now?

  • jesunkel Nov 19, 2010

    Yes, that's what prompted the PS replacement.

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3 Answers

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  • Master
  • 4,889 Answers

Looks like some kind of protection fault, the source of which can be determined if you can tell me how many times the power light blinks in between each pause.

Posted on Oct 16, 2010

  • 3 more comments 
  • eagle338
    eagle338 Oct 20, 2010

    No I am not talking about the period here. The power light is flashing right? It flashes a certain non of times followed by a pause then flashes again and so on.. I want to know how many times does the it flash between each pause. I can pin-point you to the location of the problem if you can tell me this.

    Sai.

  • eagle338
    eagle338 Oct 21, 2010

    12 blinks is a very familiar issue. It is related to the power supply board. The usual cause of this problem are faulty caps of high capacitance rating(>1000uF) . Look to see if you can find any of them bulging or cracked at the top or have tiny holes. If you find any replace them and that will most likely resolve your issue.

  • eagle338
    eagle338 Oct 21, 2010

    Does your multimeter have capacitance measurement capability? If yes then please set it to capacitance mode and range 10mF. See if it reads an over load. Sometimes the defects are too minute to be identified by visual observation. So multimeter would be the way to go. I am confident coz I have seen this before.

  • eagle338
    eagle338 Oct 22, 2010

    If so then please get me high res image of the board so that I can have a look.

  • eagle338
    eagle338 Nov 17, 2010

    Did you see page 42 of the Service manual given to you by Ginko before replacing? It has a flowchart that summarizes your problem

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  • Panasonic Master
  • 19,396 Answers

Hi.

This TV (TH-42PA20U) has internal fan, that is reported in service manual. The 11 blinks is indeed P or PA board fan.

As probably explained the TV is in protect mode. Protect mode starts when a fault is detected. The second click that you hear is the protection switch turning off the PSU higher voltages to prevent further damage. Only the low standby +5v or +3.3V is allowed. As a result the TV will be forced to stand by.

As probably already mentioned, the 11 blinks means a problem with fan or fan control. Fan is tested energizing it and reading volts at connector.Fan control is located on PA board (DC/DC secondary PSU). This is a DC 15V circuit. A diode (D574) and the +15V transformer must be tested, along with the fan. +15 V coming from power board must be OK and steady.
The fan itself is rarely the problem, most of the time you have to test at component level to find the fault.

Here layout:

blinking power light.  same even after unplugging - c8daa64.gif

Here a suppletive service manual including circuit diagrams.


If you repute my solution helpful, then please take some times to accept the solution. Providing good repair tips requires time and skills, and your feedback is important for us.

Regards.

Ginko.

Posted on Oct 16, 2010

  • Ginko
    Ginko Oct 27, 2010

    Hi.

    The service manuals clearly say that there are 4 fans in this model! Fans are +5 and +15V.

    From

    TITLE:

    Panasonic Services Company
    National Training for
    TH-42PX20U/TH-50PX20U
    TH-42PA20U/TH-37PA20U
    Plasma Display Panel


    I quote from manual:

    1) this must be tested, there are 4 fans (pg38):

    "Under normal conditions, the voltage drop derived from the voltage divider
    circuits at the base of Q9714 or Q9716 is enough to turn the transistor on.
    However should the voltage drop decrease, Q9716 or Q9714 respectively, turn
    off, allowing the 5 volts at their collectors to forward bias transistor Q9715. This
    effectively grounds pin 3 of the CPU triggering the shutdown condition.
    The four ventilation fans are monitored to be sure they are operating properly. If
    one of the fans opens or increases resistance, the resulting current change is
    applied to pin 37 of the main CPU.
    The Scan and Sustain voltages on the SC and SS boards are monitored in a
    similar manner. The +15V Line on the SS board is fed to a voltage divider and
    the result is compared to a reference voltage."

    2) this must be tested (pg36):

    "The DR15V source
    The diode D574 converts the AC output of the secondary windings of the
    transformer T502 to DR15V. This voltage source is applied to the SC and SS
    boards for Scan and Sustain operations. The PA board and fan control circuit
    also uses the DR15 voltage source. "


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  • Master
  • 10,515 Answers

Hi,

As you have tried unplugging the TV for few minutes without any success, this would confirm that this is an internal fault and repair is needed for the same. If the set is under warranty, get it replaced or repaired at no cost. However, if it is out of warranty, either you could call a tech on site to get it repaired or you could go for DIY ( do it yourself ).You need to open the TV, might need to use multimeter or soldering iron. I would also send you the link where you could purchase the service manual as you need schematics to know the exact value of each and every component.If you want to fix it yourself, kindly provide few more details :-

1. When you press power button, do you get 2 blink pause 2 blink error?
2. Do you have anything hooked with TV with HDMI cables?


If you have HDMI cables attached, you need to remove and then unplug the TV for few minutes, say 15 minutes and then turn it on. If the problem persists, we need to move further and try to fix this problem.

Let me know,so that we could proceed.

Hope i helped you.

Thanks for using ' Fixya ' and have a nice day!!

Posted on Oct 09, 2010

  • 1 more comment 
  • taran_2005
    taran_2005 Oct 09, 2010

    Thanks for your response!!

    You could buy the service manual from :-

    http://www.tradebit.com/filedetail.php/4...

    Kindly revert with more details :-

    1. When you press power button, do you get 2 blink pause 2 blink error?

    Kindly revert, so that we could proceed and fix this problem.

    Let me know,so that we could proceed.

    Hope i helped you.

    Thanks for using ' Fixya ' and have a nice day!!

  • taran_2005
    taran_2005 Oct 09, 2010

    Thanks for your response!!

    11 blinks indicate a problem with Fan SOS PB Board.

    Closer to a $150 repair if just the fan, you may even be able to change yourself for less.

    I
    would advice ringing around your local repair places and detail the
    fault light indicator and your interpretation and get them to price a
    fan replacement.There are thermal sensors throughout the TV, when a section starts to
    overheat it indicates a thermal problem in that section (in your case
    the PB board). It could be due to a failed fan, but it also can be due
    to a build up of dust in the vents and through the TV. You would have
    nothing to loose by unplugging from the wall and vacuuming the vents and
    ideally taking the back off and vacuuming in there as well.

    Let me know,if needed further assistance.

    Hope i helped you.

    Thanks for using ' Fixya ' and have a nice day!!

  • taran_2005
    taran_2005 Oct 10, 2010

    Thanks for your response!!

    I have a generic guide for all Panasonic EDTV plasma's. So, as you hear a relay click sound, i would like you to check the power supply board. Visually check for any bad / leaked / swelled caps. They might have ammonia kind of odor. Check the voltage across different points and let me know the result so that we may proceed.

    Let me know,so that we could proceed.

    Hope i helped you.

    Thanks for using ' Fixya ' and have a nice day!!

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