Plasma TV Panasonic th-46pz81fv don't want to power on (2 blinks code)

[frankie31]

Hello everybody !

I have a problem with my plasma TV (Panasonic th-46pz81fv).

When I plug in the AC cord, when I hit the power button, I hear the two relays clicking and the led near the button is blinking green quickly, and after 1 or 2 seconds, the relays click again and the blinking led becomes red.

I add that the 3 fans never start.

This is the two blinks code that the service manual calls "SOS 15V" detected by the D-board...


So I made some measurements :

1. I tryed to determine a short between the pin 1 (+15V) of P7 connector (P-Board) and ground : when I do my measurement the test-diode function displays 0 (like a short) but increases quickly like a cap charge...
I can not conclude if a short exists... or not.

2. The stand-by +5V on pin 5 of the same P7 connector is ok (it appears as soon as I plug in the AC cord) and stay stable when I hit the power button.

3. What is really surprising for me is that I can see the +15V on the pin 1 of P7 connector : I connect the probe of my voltmeter between the ground (chassis) and the pin 1 and I push the power button : I can see briefly the +15V on my voltmeter and it disappears quickly as the relays click off...


My analysis is : maybe a +15V detection circuit is out of service...
Or maybe an over-load on this +15V supply is detected so the protection circuit is activated not to damage this supply ?

As you can see, I can't isolate the faulty board... and I ask for your help.

Please could someone give me and advice ?


Thank you very much, François.

[tom66]

Re: Plasma TV Panasonic th-46pz81fv don't want to power on (2 blinks code)

This is a quite common mis-diagnosis fault by P board causing 2 blinks. Usually it is caused by VSUS failure. Check ALL of the fuses on the power board after it has discharged (give it 30 minutes unplugged.) You will probably find one blown for the VSUS switchers.

If not, it can sometimes be caused by MC201/MC301 cap failure, but usually this symptom is intermittent and set will work most of the time, slowly getting worse and worse.

[frankie31]

Re: Plasma TV Panasonic th-46pz81fv don't want to power on (2 blinks code)

Hello tom66 and thank you for your answer !

When you say "ALL of the fuses" it sounds like there are many fuses ; but I just can find 2 "normal" fuses (F201 and F301) that are good + one 145°C RF601 fuse (near the 2 relays) that I can not check without take the board apart (pins are on the foil side).

So F201 and F301 are good.

When I plug the probes of my voltmeter between Test_Point_5 (VSUS) and Test_Point_6 (GND) I find nothing (0V) when I plug the AC cord and when I hit the power button.


So this could be probably what you told me... Do you think checking photocouplers could answer some questions ?

[CHOOKY]

Re: Plasma LG 50PG20D

Hi my name is chooky,
Am hoping you will give me some advice to fix my plasma 50" lg.
A few have tried to fix it but not successful. I love this tv

Tv when switched on goes grey for a few seconds no picture/ no sound. Goes from green light to red light 3 times making a clicking sound
the problem got worse over time till it won't come on at all anymore.

LG repairer said can't fix no spare parts for this.
Expert electronics guy said z sus and fixed 2 bits on board and made it worse, so i said to put my bits back on z sus, then said y sus and buffers and not worth fixing.
Would be very grateful for any help...Thanx in advance

[tom66]

Re: Plasma TV Panasonic th-46pz81fv don't want to power on (2 blinks code)

@CHOOKY, please create your own thread and post there.

If both fuses are OK, try this procedure:
http://www.youtube.com/watch?v=LjpGKaBt8hg

[frankie31]

Re: Plasma TV Panasonic th-46pz81fv don't want to power on (2 blinks code)

Ok I will try what you tell me.

Just one thing about Q301 and Q302 : is it normal that the source of Q302 is shorted with its heatsink whereas the source of Q301 isn't with its heatsink (Q301 and Q302 share the same heatsink) ?


If it is not normal, which one do you think is ok ?


Thank you again, François.

[tom66]

Re: Plasma TV Panasonic th-46pz81fv don't want to power on (2 blinks code)

No, that's abnormal, and you may have found the fault. Replacing that device (Q302) ought to fix the fault; though, I'd also replace Q301 at the same time. They are difficult to replace, glued to a metal plate, but hot air will make them budge.

[frankie31]

Re: Plasma TV Panasonic th-46pz81fv don't want to power on (2 blinks code)

The more I think, the more I don't find this is logical...

How would Q302's source be shorted to its heatsink (the 16N55G is a TO220F -isolated package-) ?

I unstuck Q302 from its heatsink and the short is still present so, if there is a short, it comes from elsewhere, and it could be normal... don't you think it's true ?

... but I can not find this short on the service manual (page 43, upper right for Q301 and Q302)...

[tom66]

Re: Plasma TV Panasonic th-46pz81fv don't want to power on (2 blinks code)

The heatsink on these is earthed I think. A short from source to earth is not good, but I'd expect that to blow the fuse, or in the very least, trip the RCD/GFCI.

But before you dive in and check VSUS faults, check that the VSUS is definitely dead (it should come up before 2 blinks occurs.)

[frankie31]

Re: Plasma TV Panasonic th-46pz81fv don't want to power on (2 blinks code)

I checked the heatsink and it is not earthed ! You are right : if it was earthed, the fuses of my house would have blown !

Vsus that I measure between TP5 (Test Point 5) and TP6 (ground) is definitely dead (0.6V) ... what is funny is that if I do some on/off cycles with the power button in front of my TV, the voltmeter indicates a voltage that increases by 0.1 to 0.3V each time I hit the power button...

Now, I am looking towards MC203... (same as Q301 and Q302 but for Vsus instead of Vda and +15V).

[CHOOKY]

Re: Plasma TV Panasonic th-46pz81fv don't want to power on (2 blinks code)

Thanx tom66, much appreciated will start new thread have to work out how xxxxchooky

[newtothis]

Re: Plasma TV Panasonic th-46pz81fv don't want to power on (2 blinks code)

Thanx tom66, much appreciated will start new thread have to work out how xxxxchooky

go here https://www.badcaps.net/forum/forumdisplay.php?f=31

Click new thread at top left

[frankie31]

Re: Plasma TV Panasonic th-46pz81fv don't want to power on (2 blinks code)

Hello everybody !

I've just finished to change the TEA1611T chips + caps on my power supply board (norcal715 method) and the TV works now !!!

I really want to thank you for your help, regards, François.

[tom66]

Re: Plasma TV Panasonic th-46pz81fv don't want to power on (2 blinks code)

Nice one. Thanks for feedback.