Panasonic TX-P50VT50E completely dead!

[tom66]

Re: Panasonic TX-P50VT50E completely dead!

Can you link your service manual file?

[tom66]

Re: Panasonic TX-P50VT50E completely dead!

To me, it looks like Panasonic generate 15V main, and buck convert low power 5V from that (or use linear regulator)
The 15V is switched out when the set is in standby.

So maybe best to check 15V... there is no seperate standby...

Check voltage on the exposed pin of that diode near the small transformer, marked in blue on attachment. Near all the little caps, bottom of board. Power must be connected.

I'm expecting something like 12-16V.

Check test points in re d too.

[Moreno83]

Re: Panasonic TX-P50VT50E completely dead!

Hi Tom ,

Thx for the help , learning a lot!
This is the service manual that I'm using. Will put the PS back in the tv and measure the voltages. The highest voltage i have measured on the PS is 75V......

[Moreno83]

Re: Panasonic TX-P50VT50E completely dead!

Hmmz , i uploaded it but its not visible.

[Moreno83]

Re: Panasonic TX-P50VT50E completely dead!

Im measuring 15.9V.
The red box on the righthand side is measuring 4.48V.
Other 2 boxes are 0V.

[tom66]

Re: Panasonic TX-P50VT50E completely dead!

So you -do- have standby. How sure are you about your testing of the voltage? Maybe try soldering a wire to the pin on the bottom of the board. Also check the wire is crimped correctly (in the connector) and that there are no breaks in that cable. I've seen someone try to wall mount a set badly with bolts that were far too long. He put a screw through one of the power cables.

[Moreno83]

Re: Panasonic TX-P50VT50E completely dead!

Well i measured on connector P6 and i don't have that voltage there , so thats why i thought i don't have standby voltage. ( thats going to mainboard )

Also in the service manual it says STBY5V , i also don't measure it on P6. So yes i can measure but i didn't measure the voltage around that area!
You want me to solder a wire from that pin to pin 5 on P6?

[Moreno83]

Re: Panasonic TX-P50VT50E completely dead!

Also , I'm measuring 15.9v on the blue box but not 15.9v on connector P6? ( Wich also says 15v ).
This means that there is a short on the power supply somewhere right? Cables are all fine! Im not good with schematics yet but I'm also not that stupid

[tom66]

Re: Panasonic TX-P50VT50E completely dead!

Also , I'm measuring 15.9v on the blue box but not 15.9v on connector P6? ( Wich also says 15v ).
This means that there is a short on the power supply somewhere right? Cables are all fine! Im not good with schematics yet but I'm also not that stupid

No.

The power board generates two 15V rails, FSTBY15V and 15Vc. The root source is the same 15.9V source you measure, but both use high-side MOSFETs to turn them on and off. The 5V rail is regulated from this somehow and is always active when the main power button is engaged.

The FSTBY15V is switched on/off for Active Standby (outputting recording via SCART, updating TV guide etc.) Power consumption ~20W. (If in normal standby, only 0.1W or so.)

The 15Vc is switched on (along with FSTBY15V) for RUN - i.e. displaying a picture. 15Vc is used by SC/SS and (probably) A board for audio.

No 15V at the connector simply means the power board is not in RUN or ACTIVE STBY states. No 5V indicates a fault of some kind that needs to be tracked down. I want you to solder directly to the pin to measure the voltage on a wire directly, and eliminate a possible testing error.

[Moreno83]

Re: Panasonic TX-P50VT50E completely dead!

I understand what you mean with FSTBY15V etc.
Last question , you want me to solder the 15V to 15V/P6? Or 5v stby to pin5/P6.

( my guess is 15v )

[tom66]

Re: Panasonic TX-P50VT50E completely dead!

STBY5V...
The active standby shouldn't be available yet - only the 5V STBY.

[Moreno83]

Re: Panasonic TX-P50VT50E completely dead!

I soldered a wire from STBY5v to pin5 of P6 and nothing happens. STB5V is 4.6v , little low ?

[tom66]

Re: Panasonic TX-P50VT50E completely dead!

Don't do that, you could break things!
All I wanted you to do was measure STBY5V on the pin directly, using a wire soldered to it to eliminate a measurement problem.
Don't jumper anything directly. Just one wire, connected at one end.

[Moreno83]

Re: Panasonic TX-P50VT50E completely dead!

Sorry , my bad! Cant read....

I soldered the wire to pin5 / P6 only and i read 0V

[Moreno83]

Re: Panasonic TX-P50VT50E completely dead!

Ok i feel stupid now. Measured the optocouplers in the middle of the board , input is 30V and output is 4.8 and 15.9v.
Could have saved me and you guys a lot of time!

[tom66]

Re: Panasonic TX-P50VT50E completely dead!

I am confused.
Do you get ~5V on that wire or not?
Please stop jumping around the board. I have no idea why you are measuring the optocouplers.

[Moreno83]

Re: Panasonic TX-P50VT50E completely dead!

No i don't get 5v on that wire.

[tom66]

Re: Panasonic TX-P50VT50E completely dead!

Right. So that's the area to focus on.
Since the photos are not clear enough for me to trace, you will have to trace back the circuit for the 5V STBY on pin 5 and show it on a diagram for me.

[Moreno83]

Re: Panasonic TX-P50VT50E completely dead!

Hi Tom ,

Did my best to check the 5v line. I started repairing tv's a year ago so my knowledge is not that good as yours. Im still learning and bought a plasma repair ebook today with has a lot of information about plasma tv's. ( how they work etc ). So please forgive my ignorance if i make a mistake. Took a screenshot from the service manual and measured the STBY5V voltage on the parts shown in the diagram.

From T301 i get 4.48v to pin6 on P6. This is now the ONLY voltage i have on connector P6.
From the Power Micom to pin 5 on P6 is 0V , thats the only line thats not working on the 5V line. ( I think... ) It either detects a problem or does not get a signal or IC is dead?

Pin5 from P6 ( STBY5V ) trace goes to "JA17" and from there to "R489" to pin 6 from "I552" , this is the trace looking on the back of the power supply. I think I552 is the power micom IC.

[tom66]

Re: Panasonic TX-P50VT50E completely dead!

Maybe worth checking STB5V_SW_ON.
I'm asking for a trace on the bottom of the board - follow the trace back.
Right now,this fault has nothing to do with a plasma - if this was an LCD the diagnosis would be exactly the same.
If you had a blink code or blown SN/SC board yea... but it's not... it's just power supply/main board troubleshooting.