Panasonic TX-P50XT50B blinks 4 times red LED

[Damtom]

Hi all.

New to forum.

A while ago I had few TVs to fix and information on this forum helped to solve problems and I noticed that people/ users or I would call them GURUs don't have attitude to less experienced user. That's why I decided to join this forum because I'm that less expierencied user.

My friend asked to look at Panasonic TX-p50xt50b. After power cut didn't want switch on, no reaction no led, funny enough after few hours comes back to life. From informations found online , IC U203 had to be changed and ordered this one :

http://www.chsinteractive.co.uk/elec...-spkit2012.htm

It came yesterday , I changed it , TV started as usual worked for 2 minutes then click noise like relay off sound and since then when I press ON button , red LED blinks 4 times then break and again 4 times.

Online info suggest power board SOS but on this forum it was proved few times that it doesn't have to be power board.

Can someone helped me with this issue and guide me what to check first, please ?

[Ltank]

Re: Panasonic TX-P50XT50B blinks 4 times red LED

With any problems, I always check P.S. Voltages 1st. Then check see if the main board sends command to P.S. to tell it to turn on. If not. Unplug power wait a few minutes. Unplug cable from P.S. to main. See if supply turns on. If not jumper (480 to
1k ohm resistor ) between the Std by voltage (3.3 or 5vdc depending on set) to PS_ON on P.S. board. If it still does not turn on check other pins that too may need jumping. Check for shorts on P.S. and boards attached to the output

[Damtom]

Re: Panasonic TX-P50XT50B blinks 4 times red LED

When I press ON button I can definitely hear all coils noises and then relay sound off after red Led blinks 4 times. I will check all voltages tomorrow as I will have more time.

Does anyone have a access to service manual for this TV?

Thanks

[tom66]

Re: Panasonic TX-P50XT50B blinks 4 times red LED

Worth checking if the SC board is shorted... that may cause 4 blinks on this set.

[Damtom]

Re: Panasonic TX-P50XT50B blinks 4 times red LED

hi i checked all voltages and only 5v stb is showing 4.88v otherwise all others showing 0.00v

also i had look for short on power board, there is proper short that even paths are a bit brown(see photo attached).

As I'm not experienced , can someone tell me if resistor 18 kohms suppose to be damaged, will it show 0.00 kohms or can show also different values, i does show now 5.4kohms.

i found 2 diodes with no resistance at all, also resistors next to MOSFET transistors are showing different values

I'm wondering if even is worth to fix or to get used power board from net.

https://picasaweb.google.com/lh/phot...eat=directlink


https://picasaweb.google.com/lh/phot...eat=directlink



https://picasaweb.google.com/lh/phot...eat=directlink

[tom66]

Re: Panasonic TX-P50XT50B blinks 4 times red LED

I have the board from the 42" and it has the same browning, I think it's normal.

[Damtom]

Re: Panasonic TX-P50XT50B blinks 4 times red LED

What number of your power board , is it Darfon board ??

But then why is this browning only in this part board ? If that would be due to temperature , it would have browning in other part of board.

And diodes are knackered too.

[tom66]

Re: Panasonic TX-P50XT50B blinks 4 times red LED

Well, shorts are bad. But it's normal because those resistors get hot in that part of the board.

[tw2005]

Re: Panasonic TX-P50XT50B blinks 4 times red LED

hi i checked all voltages and only 5v stb is showing 4.88v otherwise all others showing 0.00v

also i had look for short on power board, there is proper short that even paths are a bit brown(see photo attached).

As I'm not experienced , can someone tell me if resistor 18 kohms suppose to be damaged, will it show 0.00 kohms or can show also different values, i does show now 5.4kohms.

i found 2 diodes with no resistance at all, also resistors next to MOSFET transistors are showing different values

I'm wondering if even is worth to fix or to get used power board from net.

https://picasaweb.google.com/lh/phot...eat=directlink


https://picasaweb.google.com/lh/phot...eat=directlink



https://picasaweb.google.com/lh/phot...eat=directlink

R005,006,007 are in parallel so measured in cct expect 6k ohms

I would use diode mode to check diodes and even then you need to know what type of diode it is.

Resistors next to mosfets showing different values, means nothing without locations and a schematic. You would have to remove out of cct to be 100% sure if they measure correct.

I would say if you can find another PSS board used working cheap enough it may be a smarter option

[tom66]

Re: Panasonic TX-P50XT50B blinks 4 times red LED

Tw, isn't therea schematic for this board.

[tw2005]

Re: Panasonic TX-P50XT50B blinks 4 times red LED

Tw, isn't therea schematic for this board.

yep, a search B159-201 may dig it up. been uploaded a couple of times recently and I've uploaded it to elektotanya

[Damtom]

Re: Panasonic TX-P50XT50B blinks 4 times red LED

Thanks tw2005. I keep forgetting about parrell resistors.

I checked diodes in diode mode and shows 0.00 in both direction

There is one on eBay for £49.95.

[tw2005]

Re: Panasonic TX-P50XT50B blinks 4 times red LED

I checked diodes in diode mode and shows 0.00 in both direction

And it's possible they're sitting across a transformer winding which would show short if that's the case

[Damtom]

Re: Panasonic TX-P50XT50B blinks 4 times red LED

There is just that coil. U can see on first and second picture, otherwise there is nothing there.

[tom66]

Re: Panasonic TX-P50XT50B blinks 4 times red LED

Best to pull them out. Some diodes have the two outer leads electrically connected which is not necessarily a fault.

BTW, I remember now, those resistors are for the Ve supply, about 150V unregulated. 18kohm each, they'd dissipate 1.25W a piece. So that explains the board browning around them as that is fairly hot.

I guess they use them to give some minimum load to the Ve supply, because otherwise it might vary too much with Vsus/Vda load.

I do have the 42" board to make some checks on but it's at home, 300 miles away. Will be back in January if you need some checks done.

[Damtom]

Re: Panasonic TX-P50XT50B blinks 4 times red LED

The only worry I have with buying new power board is that I'm not sure for 100% that current power board is faulty. As I said before there is just 5vstb voltage and others show 0.00v. Shall I give voltages from connector to main board?



Fournd manual for b159-201

http://elektrotanya.com/panasonic_x5.../download.html

[nomoresonys]

Re: Panasonic TX-P50XT50B blinks 4 times red LED

if the only reading you get on power supply is 5 vstb, the problem is probably on your power supply.

[tom66]

Re: Panasonic TX-P50XT50B blinks 4 times red LED

if the only reading you get on power supply is 5 vstb, the problem is probably on your power supply.

Not always, can be that if the main board has not sent power on command that the power board is OK and the main board is bad. Needs to be checked first.

[nomoresonys]

Re: Panasonic TX-P50XT50B blinks 4 times red LED

Not always, can be that if the main board has not sent power on command that the power board is OK and the main board is bad. Needs to be checked first.

Indeed, was a quick judgement, needs more checking for sure.

[nomoresonys]

Re: Panasonic TX-P50XT50B blinks 4 times red LED

should he unplug the power on connector from the main board to the power supply and check for power on at the main board? not sure how that works.