Panasonic TH-P65ST60A no STBY light no backlight no power

[JohnML1975]

Hello All

Started working on this TV today
As I remove the back will share some photos and findings
The problem I am having is in the title of this thread
I still need to proceed my trouble shooting
Started a thread so that I can share with all

Any inputs are welcome

[JohnML1975]

Here are photos
There are no burn marks that I can see
The two fuses on the power board are serviceable

I need to check power on the PSU next

[JohnML1975]

Have 347 V at the main filter capacitors which have 450 V written on them
There is no power to the sustain boards even if I disconnect them
I am going to check power to the mainbaord next and leave the sustain boards disconnected

[JohnML1975]

Checked power from mainboard to PSU
there is zero voltage on all 14 pins

I used thermal camera on the PSU and could not see anything standing out

removed PSU and cleaned the dust off
looked around both sides of the PSU board

there are many cracked solder legs on the MOSFETS and transformer legs
these appear to be on the mainboard supply and the sustain board supply

so i am going to resolder every joint, except the SMD joints on the PSU
then shall refit and test

[JohnML1975]

Soldered the suspicious joints and soldered some others that did not look very good
refitted the PSU board
tried to turn on but the failure mode is the same

no power outout

going to remove the PSU again and check components with multimeter

[ivtv1]

Have you measured all the outlets for leaks with a multimeter?

[JohnML1975]

Hello and thank you ivtv1
I am not too sure what you mean
if you could clarify it would be appreciated

The PSU does not produce any power to the mainboard
the PSU does not produce any power to the two sustain boards
So I think there is a problem with the PSU

I completed checking the MOSFETS and the diodes which are through hole components
These are all serviceable

At the moment I am moving on to check the resistors

[ivtv1]

If there is a short circuit in any of the outputs of the power supply, it will not start. With a multimeter, check for a short circuit to ground.

[JohnML1975]

Thank you ivtv1

Today I placed red probe of multimeter on each of the two sustain plugs
I placed the black probe on ground
There was no shart circuit on the power side

next i powered up the board

connected to the two filter capacitors are two resistors
there is 340 V to one side of the 2.2 ohm resistor
there is no power on the other side of the 2.2 ohm resistor
when i check OHMS across the resistor there is OL showing on the multimeter
the resistor looks okay

i will remove it from the board and test it

[JohnML1975]

This is the 2.2 OHM resistor removed and tested
It says OL
In the board it measures at around 60 kilo ohms

So i think it needs a new resistor

[JohnML1975]

I fitted new resistor and the resistor just blows up; there is flash and the resistor becomes open circuit again

so i guess whatever that resistor is connected to is faulty

i shall need to trace that circuit

[JohnML1975]

I found a shorted MOSFET on the hot side of the board

I will need to remove it and test it

[lotas]

I fitted new resistor and the resistor just blows up; there is flash and the resistor becomes open circuit again

so i guess whatever that resistor is connected to is faulty

i shall need to trace that circuit

This should have been done from the very beginning, after the burnt-out resistor was discovered (resistors don't just burn out), and installing a new resistor could now damage even more components.

[JohnML1975]

Hello lotas

thank you
I should have treated the 2.2 ohm resistor the same way i would treat a fuse
next time, i will do that

meantime, i have found the shorted part and shared a photo
each leg is shorted to the other leg
the voltage drop is less than 0.03 volt when the DMM is in diode mode
when i check the board the short is now gone

i am going to order the new part