panasonic tx-p50s10b

[paulstef]

Re: panasonic tx-p50s10b

GOOD!

The uCs need 3.3V. If they don't have it they won't do anything.

Checking the schematic....

In the meantime you could power off everything and see if you have a short from this 3.3V line to GND.

[paulstef]

Re: panasonic tx-p50s10b

Mmh, ok, THIS 3.3V is switched. The signal to turn it on comes from another uC.

We need to check first IC5480 input and output voltage.

[ronhayes]

Re: panasonic tx-p50s10b

It is not shorting to GND.

[paulstef]

Re: panasonic tx-p50s10b

It is not shorting to GND.

Nevermind. This 3.3V signal depends on another signal. See previous post.

[ronhayes]

Re: panasonic tx-p50s10b

Sorry Paul
This IC was on the other side of the board.
I am getting 4.25v on pin 7 and 0.24v on pin 8 of IC 5408.

[paulstef]

Re: panasonic tx-p50s10b

Measure resistance from pin 8 to gnd (turn off power before).

This chip, according to the block diagram on page 30, should create 3.3V from the 5V standby voltage. It doesn't so it's possibly either defective or there is too much load on the 3.3V output.
It also does some other stuff and I don't know if any wrong signal or shorts or anything on the other pins could affect the 3.3V regulator.

[ronhayes]

Re: panasonic tx-p50s10b

It is 03.3 in the 200 range checked with two different meters both reading the same.

[paulstef]

Re: panasonic tx-p50s10b

You mean 3.3Ohm on the 3.3V output pin 8 to ground? That's too low. Ideally we would now try to isolate the pin. :-D

You see that from pin 8 there is one trace going underneath the chip and goes then to a via to the other side of the board (unless it's a multilayer board, I don't hope so). Obviously you cannot cut a trace on this side. So you need to find the same via on the other side and then there is hopefully only one trace going from that via. That trace you would need to cut. Pin 8 is then isolated and you can you determine if the 3.3Ohm comes from the chip itself or from somewhere else.

Actually not difficult.

[tom66]

Re: panasonic tx-p50s10b

I have had that Panasonic multi-voltage IC fail on a PZ80 before. It generates some reset signals too, plus has over-voltage comparators... It's difficult to get hold of as it's a custom Panasonic IC. One supplier in Italy @ £10 each incl postage.

In my case the IC was bad because of a power surge through the HDMI ports, it had damaged one port and I guess the surge current had propagated through to other parts probably through the ESD protection networks, other damage made the board unrepairable (I replaced the IC but it failed immediately due to a shorted load, no current limiting...)

[ronhayes]

Re: panasonic tx-p50s10b

I see what you mean Tom.
I will have closer look at the ports tomorrow Tom.
I think my best way to go with this one is maybe a replacement board, depending on cost.
The problem with these sets is of course are they worth the cost of the repair due to the age and cost of new TT'S these days.But If I can locate a replacement board for the right price then maybe I will carry on maybe.

[ronhayes]

Re: panasonic tx-p50s10b

Hi Paul/Tom
Having a close look at this board i cannot see any visible damage near any of the ports although that doesn't mean there isn't any, and checking to see where the track goes underneath the IC is very difficult and most of the tracks are so close together on both sides of the board and and going by the poor state of my eyes these days, I think it would be better to see if i could source either a replacement IC or complete board which ever would work out the cheapest. The only problem with changing the IC is would this bring it back to life or not would be a gamble?

[tom66]

Re: panasonic tx-p50s10b

Well, the picture performance of a good Panasonic plasma is very good, so I would say yes, they are worth saving, but it obviously depends on what you want to do. If it's a customer's TV, they probably won't bother with the repair... 6-7 year old plasma TV, even if it's better than 99% of the other TVs out there...

[paulstef]

Re: panasonic tx-p50s10b

We could at least try to find out if it's this chip or not. Because if it's not than online troubleshooting will be become so difficult you are really better of buying a new board.

I've seen that IC for just a few dollars somewhere, have to find the link.

I'll try to find that trace on the other side for you...

[paulstef]

Re: panasonic tx-p50s10b

Bad news. It's definitely a multi-layer board. The trace goes from pin 8 of IC5480 underneath the chip and to a via. The same via is connected to C5513 on the other side nowhere else. That means ST3.3V must be distributed on an inner layer.


Since you said your eyes aren't that good anymore I assume you don't want to try slightly lifting pin 8 from the board, right. :-)

There are some other things we could try but I think it's getting more complicated now.

[ronhayes]

Re: panasonic tx-p50s10b

Paul
Just out of curiosity i thought i would have a go at lifting that leg using a needle and fine tip soldering iron and i managed to lift it ?

[paulstef]

Re: panasonic tx-p50s10b

Paul
Just out of curiosity i thought i would have a go at lifting that leg using a needle and fine tip soldering iron and i managed to lift it ?

First I would remove the solder from that pin with solder wick. Then yes you could use a needle and slightly forcing it up while heating the pin/pad.

Don't lift it up too much otherwise you may break the pin when pulling it down again.

You should then be able to measure resistance again and determine where the 3.3Ohm come from.

[ronhayes]

Re: panasonic tx-p50s10b

Paul
I have checked it and the it appears the 3,30 ohm is from the track and not the 8 leg but it is a slight difference now it is reading 3.10 ohm as apposed to 3.30 ohm.

[ronhayes]

Re: panasonic tx-p50s10b

Was just wandering could you install a A board from a 42" panasonic with the same model number and go into service setup and change it for a 50" or must the Aboard be from a 50" only ? As the only ones i have seen so far are for a 42".

[tom66]

Re: panasonic tx-p50s10b

You can but you would have to swap over the panel data flash or the panel might not work properly (maldischarge) this will involve surface mount soldering

[paulstef]

Re: panasonic tx-p50s10b

3.3V goes to several places from there.
Does the short on the trace still exist when you remove the cable that goes to the power button,IR sensor assembly?
That's supposed to be connector A1 on the A board.

See page 31 of the SM.