Panasonic ST50

[johna8]

Re: Panasonic ST50

Ok so not going well - the looping has reappeared.
Video uploaded to here - http://******/2kddEya

Any ideas what I can test during this looping ?
I can check the 5V line but if it's ok then is it safe to say PSU is ok ?
Would the culprit be the main board?

[johna8]

Re: Panasonic ST50

Not really much luck with the hair dryer although I only did it for say 2-3 minutes on certain areas of the power supply.

If you see the photo I uploaded it almost looks like part of the pins looks a little rusty etc?
Don't know what else to do. I'm happy to replace the power supply first and then the main board if required.

[Moreno83]

Re: Panasonic ST50

Ok , im thinking the mainboard is the bad guy here. Try to heat up the mainboard and turn it on.

[dskall]

Re: Panasonic ST50

I agree with Moreno83 that it is a mainboard, not that i'm even in the same league. I'm a mere beginner and would follow his advice first. I did although fix a different make with a cycling problem by heating/cooling mainboard around input connectors where the different voltages for main board are produced. Was able to narrow it down to a smd cap on the output of voltage regulator. Replaced and all was good.

[Moreno83]

Re: Panasonic ST50

Thanks for jumping in and as i said before , i think its a mainboard problem. The problems with the mainboards from Panasonic are usually BGA problem ( solder under cpu ). I think heating up the mainboard for 2/3 minutes close range will probably turn the tv on.

Look at the picture from the service manual. the ST50/GT50/VT50 mainboards all work the same way.
Mains voltage is going into the power supply which generates EV5V only , nothing more is coming from the power supply.

EV5V is going via pin 6 to the mainboard into IC2002 to Q2002/2004 etc. If that ic is not doing its job you won't see a standby led and the tv is completely DEAD.

[johna8]

Re: Panasonic ST50

Replaced the power supply.

Just an update, TV is working fine.

Prior to replacing the PSU - any Service Adjustment - testing through the colours/patterns would trigger the TV to just reboot or restart (and then eventually the power on looping).

With the replaced PSU - I can leave the service adjustment menu on flicking through the tests without any issues so far.
This would've failed within a few minutes but this has been on for the past hour.

The only subtle difference I noticed when the TV was on with the new PSU is on the P6 reading I was able to read a value off pins 1,2. Perhaps the fault was the areas providing to Pins 1-2 off P6.

Pin 1-2 = 3.3V (taken only when the TV was switched on).
Pin 6 = 4.48V
15vc and 15vs = 15.73V (same as the old board)

I might see if there's anyone who can review the older PSU and replace any failing components so I have a spare (although this may might be cost prohibitive). From the pictures uploaded previously any specific areas to review off the PSU?

I've obtained a spare mainboard, 2 power supplies for $150 NZD which is great. This TV is going to last a while yet longer.

Does the ST series suffer from like you said the BGA failing (having a spare mainboard will be ideal).

Thanks all!

[Moreno83]

Re: Panasonic ST50

Hi John ,

Good thing you fixed the tv. It was either the powersupply or mainboard , it all depends on the 5V and if the mainboard returns the voltage. Glad you fixed it and you got some spare boards.

[johna8]

Re: Panasonic ST50

Noticed in the tests just this one little pixel which appears to be stuck on one colour.
It's not really visible from watching the TV but would this be the panel itself causing it ?

[Moreno83]

Re: Panasonic ST50

Could be panel issue yes. Do you get the same with a movie?

[johna8]

Re: Panasonic ST50

3 HDMI inputs (3 devices), Digital TV, Media Player - one red stuck pixel lucky its in the upper right corner.