Panasonic TX-P50STW50 Power Supply no 5V (was clicking)

[Ierwin]

Re: Panasonic TX-P50STW50 Power Supply no 5V (was clicking)

Thank you very much for looking into this.
I hope I can provide some more measurements later when I am at the board, but for now I can at least give an update from memory.
Since the 2
2Ohm resistor was replaced ic200 seems to perform well. It's getting 310Volts on the HV input and if I remember correctly is outputting 15V.
What I have done since my last post:
I disconnected the output leg of the 5v voltage regulator from the rest of the circuit.
With this connection open the regulator has 7.2V on the input and 4.6 on the output.

I suspected the regulator to be faulty and used a 78S05cv as a temporary replacement just to see what it does. This also causes the voltage on the input line of the regulator to drop and the output of this regulator is about 3,5Volts.

I suspect that either the input of the regulator is lacking Power so the voltage drops under load or a short on the output side of the 5v regulator.
Actually I think it is the first because I connected an external power supply to the 5V circuit and the circuit was pulling about 250mA (not connected to mains),which seems reasonable an not like a short.

Maybe the error is on the primary side of T200. If I remember correctly Q110 is involved there as an amplifier of the driver output of ic200. Oh by the way ic200 is a 34A65.
I had previously checked Q110 for shorts bit it seemed ok.
If you need more measurements or Pictures let me know

[dskall]

Re: Panasonic TX-P50STW50 Power Supply no 5V (was clicking)

So what voltage are you getting on pin 8 of ic200? If no voltage and 2.2ohm is burnt again check Q110 for shorts.

[dskall]

Re: Panasonic TX-P50STW50 Power Supply no 5V (was clicking)

So RL100 makes no sense. Appears to short input. 5.5v into regulator is not a good voltage. Need pictures. Also # off ic200

[Ierwin]

Re: Panasonic TX-P50STW50 Power Supply no 5V (was clicking)

I made some progress yesterday so I want to give an update.
A little breakthrough was made when I finally flipped to page 2 of the datasheet of the IC 34A65 (IC200 "STBY Control").
When I saw the example circuit I finally realized why I had been tracing in circles all across the noard for hours and hours.
The Standby Cotrol IC is driven by high voltage!
So basically the rectified main goes right into this IC over some resistors.
Once I understoof that I quickly found that one of the Resistors (R224, 2.2Ohm 2W) had failed. I have no Idea how since it shows no sign of burn or whatsoever, but it has unlimited resistance so its definetly gone.

I replaced the Resistor and suddenly everything came to live.
5V on the mainboard connector as well (YEAH!)

I was at my parents place and only had the Powerboard with me, so I once again connected 5V to Panel_Main_On, STB5V_ON and F_STB_ON using 1KOhm Resistors. After some initial Clicking and Clacking the relay just made a single "Click" when I connected main.
I think at that point the Powerboard was actually fully working and hat it been inside the TV I think it would have started.

But I had to get the board back home first. And back here its stupid thing doesnt want to play along anymore.
No 5V on the connector.
IC501 (linear voltage regulator) is getting 5.5V on the input side but does not output anything.
Could it be gone? Could it have been slowly failing all this time? Or maybe there is a short that pulls down the output voltage? Is 5.5V even enough for the voltage regulator to properly work or should I be looking in front of it?

[Ierwin]

Hello everyone,

Ive been a member of this forum since 2017 and always found so much useful informaiton that I never even had to ask questions myself. Now I have a TX-P50STW50 Panasonic Plasma TV on my desk that I just can not make sense of.
As a little disclaimer: English is not my first language so please bear with me in case I do not always use the correct technical terms.

So the previous owner of this set told me that the TV started clicking and restarting every now and then. These events got more frequent until it became completely dead. No reaction whatsoever.

When I first got it suspected some of the caps that are close to the heatsinks to have leaked. They were not buldged or anything but they had black spots on the top that in retrospect may have just been black marker. But since I had them in the drawer I replaced them.

After refitting the Power Board and about one minute after I had plugged everything in, the relay started clicking, but the tv wouldnt start up. I unplugged all other boards from the power supply and started to look for the voltages (there is very good documation in the service manual: ).

So on the Plug P6 (see Manual Page 48) there was 5V on Pin 6 (STBY). I disconnected all boards from the PSU and connected these 5V to Panel_Main_On, STB5V_ON and F_STB_ON using 1000Ohm Resistors each.
This resulted in exactly the same continous clicking.

I then went ahead and looked for teared soldering connections and found a couple that looked suspicious. I resoldered some when I made a (probably) big mistake.
Of course I had discharged all the bigger capicators before I started to work in the PSU with a soldering gun. But I must have missed one of the smaller ones that still had a charge.
So I was trying to resolder the central Pin of Q110 and I was working from the top of the board as it is exposed there. When I applied the solder I accidently touched the heatsink and caused a little spark. I am almost certain that the short must have been between the central pin of Q110 and the Heatsink.

So this is where I am now. Ever since this incident the clocking is gone. The PSU seems completely dead, no 5 Volts no nothing.
Ive been trying to understand the 5 Volts generation circuit all day but just can't make sense of it. I am pretty sure that whatever is causing the 5V to fail atm is just caused by my dumb mistake and not even the root cause of the tv breakdown, but thats the first step that needs fixing.

So I traced all over the place. To my understanding IC501 is some kind of linear voltage regulator that I think is one of the most important part of the 5v generation. Pin 1 should be VDD and is simply connected to Pin 9 of the Transformator T200 over a Diode.
However there is no Voltage on this Pin, so whatever the problem is, must be on the primary side of T200.
Im having a hard time understanding in which order these components are supposed to come up. For example the IC200 "STBY CONTROL" does not have Vcc either.
I think I must have killed something in the part that generates the primary current on T200. There are several SMD transistors involved here and the only one I think I have confirmed working is Q200. This has 5V on one pin and apparently is switching to Gnd and I think this is what it is supposed to do.

I would really appreciate if someone whith more knowledge could take a look at the shematics and help me trace this error.

Best regards

Kolja