Viera 42 inch LCD,not firing up Looking for a bit of help ..

[ceedy]

Re: Viera 42 inch LCD,not firing up Looking for a bit of help ..

Can you use diode test?

Open diode is rare, most common is shorted.

-----------------------


Diode test selected on fluke ..red to Centre lead black on outer leads
reads 300ohms initially then value rapidly increases til Open circuit .then stays there
til ,
reverse the leads and the opposite happens OC down to 185ohms ish .

this doesn't happen on the other 2 en220a's .
does this make sense ?

Chris

[tom66]

Re: Viera 42 inch LCD,not firing up Looking for a bit of help ..

Can you try on the diode test mode?

[ceedy]

Re: Viera 42 inch LCD,not firing up Looking for a bit of help ..

Can you try on the diode test mode?

can I go .. doh! and double treble doh!!!

and go back a few messages .

Just forget all my references to ohm .. and read .. v in diode test

..

blame it on xmas stress or ongoing senility

C

[tom66]

Re: Viera 42 inch LCD,not firing up Looking for a bit of help ..

OK, 300mV is fine, but open is not. What is the part # on the device?

[ceedy]

Re: Viera 42 inch LCD,not firing up Looking for a bit of help ..

OK, 300mV is fine, but open is not. What is the part # on the device?

EN220a

[tom66]

Re: Viera 42 inch LCD,not firing up Looking for a bit of help ..

OK, probably this part:


Across pins 1-2 and 3-2 you should have about 300~500; but you are saying on both you see nothing?

[ceedy]

Re: Viera 42 inch LCD,not firing up Looking for a bit of help ..

OK, probably this part:


Across pins 1-2 and 3-2 you should have about 300~500; but you are saying on both you see nothing?

it starts at 450 ish then rises to over 2v then goes oc

its got completely differing results to the other 2 En220a diodes on the same heatsink.

is it ok to test on the board or better to remove and test ?

[tom66]

Re: Viera 42 inch LCD,not firing up Looking for a bit of help ..

It is better to remove in this instance.

[ceedy]

Re: Viera 42 inch LCD,not firing up Looking for a bit of help ..

It is better to remove in this instance.

its out .

in diode test . pos to pin 2 neg to 1 or 3 = OC

neg to pin 2 pos to 1 or 3 = .190-.210

Also taken out the other two , and these give almost identical readings


C.

[tom66]

Re: Viera 42 inch LCD,not firing up Looking for a bit of help ..

Diode is good... time to look elsewhere.
Without a pin out of that connector it's pretty hard to figure out the on/off (pson) pin.

[ceedy]

Re: Viera 42 inch LCD,not firing up Looking for a bit of help ..

Diode is good... time to look elsewhere.
Without a pin out of that connector it's pretty hard to figure out the on/off (pson) pin.

well at least they've been out to stretch their legs ..groan!!

The Power switch/power led/Remote IR wires all connect at this point on the main board.

[ceedy]

Re: Viera 42 inch LCD,not firing up Looking for a bit of help ..

Found this ..manual .. its uses the same Mainboard and the Wiring and connectors are the same numbers and positions.. but the power board has a different layout , but it may give some connection info .?
http://elektrotanya.com/panasonic_tx.../download.html

C.

Will be happy to pay for a manual if I can find exactly the right one . lots I've come across are just similar !

[tom66]

Re: Viera 42 inch LCD,not firing up Looking for a bit of help ..

I will have a look at that.

[ceedy]

Re: Viera 42 inch LCD,not firing up Looking for a bit of help ..

even better this one ... seems very close..

http://elektrotanya.com/panasonic_tx-l42u10e.pdf
/download.html

has the right boards !!

Chris

[tom66]

Re: Viera 42 inch LCD,not firing up Looking for a bit of help ..

Ah, well, 4 blinks on this model means A Board fault: SUB_F_12V

See page 56 of SM. I've copied it over to my site for easier access (ET is a pain):
http://www.tgohome.com/ServiceManual...&Search=Submit

Although it says "A Board" I am not sure, as it appears to come directly from the PSU.

Does the relay click when the TV turns on?

Check pins 4 and 5. They should change when TV attempts to power up.

[ceedy]

Re: Viera 42 inch LCD,not firing up Looking for a bit of help ..

Ah, well, 4 blinks on this model means A Board fault: SUB_F_12V

See page 56 of SM. I've copied it over to my site for easier access (ET is a pain):
http://www.tgohome.com/ServiceManual...&Search=Submit

Although it says "A Board" I am not sure, as it appears to come directly from the PSU.

Does the relay click when the TV turns on?

Check pins 4 and 5. They should change when TV attempts to power up.

---------------------------------------------

Relay clicks when power B pressed and clicks (off?) after the green LED blinking. and just before the 4 x blinking..

Pin 5 ( tv_sub_on ?) shows 0 v all the time . no change when P but pressed.

Off to take grandson to Doctors so will vanish for a wee while !

Chris

[ceedy]

Re: Viera 42 inch LCD,not firing up Looking for a bit of help ..

[QUOTE=ceedy;295108]---------------------------------------------

Oops typo ..

Relay clicks when power B pressed and clicks (off?) after the green LED blinking. and just before the 4 x blinking..

Pin 4 ( tv_main_on ) shows 0 v all the time . no change when P but pressed.

Pin 5 ( tv_Sub_on) jumps to 2.53 v when P-But pressed then drops to 0v after relay clicks off.

[tom66]

Re: Viera 42 inch LCD,not firing up Looking for a bit of help ..

OK, so when the 2.5V comes up, you should see 12V, 17V and 24V come up. Do you?

TV_MAIN_ON controls the PFC.
TV_SUB_ON controls the 12V/17V/24V.

If not, locate capacitor C835 near IC802. I think it will measure around 21V if it is working because the circuit near it is a 21V regulator (formed using an NPN transistor and zener diode.)

If that measures 0V, check C843, which should measure a bit higher than 21V. IIf that's good, suspect the zener diode D823 or transistor Q804/Q805.

The IC802 is sold as a spare part: http://richtechparts.com/i-4099-MCZ5203D.html
in case that turns out to be the problem.

[ceedy]

Re: Viera 42 inch LCD,not firing up Looking for a bit of help ..

[QUOTE=tom66;295128]OK, so when the 2.5V comes up, you should see 12V, 17V and 24V come up. Do you?

TV_MAIN_ON controls the PFC.
TV_SUB_ON controls the 12V/17V/24V.

If not, locate capacitor C835 near IC802. I think it will measure around 21V if it is working because the circuit near it is a 21V regulator (formed using an NPN transistor and zener diode.)

If that measures 0V, check C843, which should measure a bit higher than 21V. IIf that's good, suspect the zener diode D823 or transistor Q804/Q805.

----------------
Press p-But and Cap C843 goes to 18.7v then to 0v after relay clicks off.

[tom66]

Re: Viera 42 inch LCD,not firing up Looking for a bit of help ..

OK C843 looks good (that circuit may be used as a limiter, not necessarily a regulator.) But you are saying you get nothing on the C835 output? Check the resistance between the leads of C835. I suspect the IC has a short across Vcc and GND (which it is in parallel with.) The IC may therefore need replacement.