Panasonic ST50

[johna8]

My lovely 5 year old plasma is starting to fail.

I have this happening to my plasma: https://www.youtube.com/watch?v=GUc-91Vcdbk

It will keep looping, if I disconnect the main power for say 10-15 mins, then I can power the TV on fine.
Can last for around 10-15 minutes, and will keep restarting itself but will remain on fine.

My guess it's the power supply TNPA5567 (mine is version AF) but keen to find out would majority of the power boards be 90-240V? (as these TVs are sold worldwide). Given I'm in New Zealand trying to source a replacement TNPA5567 AF power supply board might be a bit troublesome.

No specific error blinking leds or red lights at all. Just the green power on led will flick very fast so unable to do the proper count for the error code.

Anyone else dealt with this issue and was it simply a replacement power board?

Regards,
John

[Moreno83]

Re: Panasonic ST50

This is a tricky one to be honest. This is either powersupply or mainboard.

Personally i would think the powersupply either works or does not work. In this case 5V goes to the mainboard and the mainboard turns on the rest of the tv......

But what is failing?

You could try and resolder all the suspicious parts on the powersupply and see if that changes anything.
You seen any abnormal picture?

[johna8]

Re: Panasonic ST50

Thanks - no bad or failing picture.
Just sometimes the Tv won't power on at all (3 audible clicks).
The easiest part I can source in New Zealand is a replacement power supply.

Sometimes the logo won't appear at all and so just the audible clicks when trying to switch on.

[dskall]

Re: Panasonic ST50

You will need to post pictures of back of unit and clear pictures of boards. You also need to post voltages in standby and when powered on

[Moreno83]

Re: Panasonic ST50

With these models the power supply only gives 5V standby to mainboard , thats it. If he measures 5V then PS is working. PS is working because the tv tries to turn on. My personal feeling is you have a bad mainboard.

Only way to test is to swap out boards OR measure everything on the white connector going to the mainboard when you turn on the tv. Do you get a steady 5V?

[dick_barton]

Re: Panasonic ST50

Some clear sharp pictures of your power supply would be useful. After 5 years solder joints do start to fail and also capacitors on the psu.

[Moreno83]

Re: Panasonic ST50

True but not with Panasonic plasma from 2013. Solder joints maybe but definitely not capacitors. The set won't produce enough heat on the PS in that short period of time.

I suspect BGA solder on the mainboard cpu because the CPU is the first thing that gets hot.

[johna8]

Re: Panasonic ST50

Thanks all for the feedback.

My workaround of disconnecting the power (for say 5-10 mins) doesn't seem to be working any more.
TV will not power on at all any more. Red light (standby) will be on once the power is returned, however switching on the TV the green led is missing and nothing can be heard from the TV.

Given my symptoms are very close to the YouTube video - his issue was related to the power supply. If I do manage to borrow a multimeter I will test the voltages.

[Moreno83]

Re: Panasonic ST50

Ok , you only got a red standby led? That means the PS is giving the 5V but the mainboard does not turn on the power supply.

You can measure the voltages on the white connector going to the mainboard. Black prope on ground and red prope on the pins. Measure in DC voltage.

[johna8]

Re: Panasonic ST50

Thanks for the guidance.

Here are some photos here: http://******/2kddEya
Don't think there are any bad caps / loose screws etc - looks pretty good in general.

So I did a test with a multimeter.

AC input into power board returning 237/248V.
However then at the Y and X power outputs.
Standby (red led) - 00.1 / 200V
Turned on (no red led) - only 00.2 to 00.4 / 200V.
Power -> Mainboard (Video inputs) - nothing at all has a label 15V - could not obtain any readings at all.

This would appear to be a power source issue? Odd I don't get a good reading if at all on the X / Y DC outputs. The fuses I haven't bothered to check.

[dskall]

Re: Panasonic ST50

Ok I am new and just learning TV repair. I am confused when you say that if the power board has 5v standby the power supply is good. I have not seen a power supply with just standby. All power boards I've seen especially plasma has numerous voltages. Am I misreading something?

[dskall]

Re: Panasonic ST50

Here is a link to troubleshooting guide

[johna8]

Re: Panasonic ST50

Sorry I also forgot to mention ever since the TV was failing - not once did I have any red blink codes at all.

[Moreno83]

Re: Panasonic ST50

No , you need 5V on the white connector going to the mainboard. How else is the mainboard getting power?

5V into mainboard , mainboard turns on the rest of the power supply and THEN power will go to the SS/SC boards so yes its normal that you don't measure anything because you don't even have LED.

So back to the beginning. Do you get 5V on the white connector? Its probably the only voltage you will measure when the tv is off.

[johna8]

Re: Panasonic ST50

Any ways to report back - after having TV disconnected overnight.

The TV is now powering on again - sigh.
So I tested again and when switched on the readings from the power to mainboard - with it switched on.

15Vc - 15.73V
15Vs - 15.73V

Tested 5V - pin 6 - reading only 4.50V - should it be over 5V?
I did notice that when I replug in the power, about 2-3 minutes later I hear a click but not sure if related to having the ability to power on or not.

This would mean that the intermittent issues could be caused by the main board rather than the Power Supply?
I did notice a slight buzzing sound from the power supply when the unit was on (green) but apart from that.

Everything else is fine picture, etc - just when it won't switch on there are no red blink fault lights at all.

Here is a diagram of the P6 plug I measured - pins 13,15 and 6.

[Moreno83]

Re: Panasonic ST50

Those readings are fine. Its not always correct 15V or 5V. For example 5V can be 4.8v.

All connectors are seated correctly?

[Moreno83]

Re: Panasonic ST50

IF the Ps is the problem here i would suspect one of the optocouplers or the solder on the transformer(s). Optocouplers are the 6 small parts between the transformers.
Could you please try the following when the error occurs again? Use a hairdryer and heat up the power supply. If the tv turns on immediately then your PS has issues.

[johna8]

Re: Panasonic ST50

Yes all the connectors are fine internally but I will reseat.
I do find it odd that I don't get any red blink fault lights at all when the issue occurs.
If the PSU is playing up again, I will try and measure the 5V line again now that I have the readings.

Any other suggestions on what to look out or test for?
I did upload the photos of the boards of my unit - ****** link prior.

[dskall]

Re: Panasonic ST50

You can try heating or cooling one board /area at a time to see if a thermal issue. A lot of times intermittent problems react to temp variations.

[Moreno83]

Re: Panasonic ST50

I do find it odd that I don't get any red blink fault lights at all when the issue occurs.

That means you don't have 5V going to the mainboard or the mainboard is acting up. So when the fault occurs you need to measure for 5V on Pin 6 on the white connector. If 5V is present and you don't get a LED or does not turn on with power button then mainboard is "dead".

I see you found the training manual for the 50ST50. Go to page 30 and follow instructions but a dead set is usually mainboard.