Saturday, June 16, 2018

Panasonic TX-P42X50B Plasma TV

              I`m no way a TV repairman but I`ll always have a go to help. This set was brought to me by a work colleague with a power up issue. When the TV was off and unplugged for a while it refused to switch back on. No Red power light, nothing, dead so to speak. I thought the usual, bad caps, loose connections, loose ground screws or something along those lines.






         Well looked after and a nice set I had my fingers crossed. Off with the back cover!
Note to self, wear gloves next time as the cover is razor sharp. 



         Top right in photo, PSU board would be my first investigation. I needed to get it out and flipped over as apart from a few dust bunnies this thing is clean as a whistle.


        Before any repair I tend to ignore Google or Youtube for leads as they can send you on a wild goose chase through some complicated scenarios that you don`t see the wood for the trees. I checked input and standby voltages which seemed fine, no apparent damage here on the surface. Removed the PSU board to look underneath!



        As you can see on the bottom right we have discolouration, heat build up. Bad resistance coil connections (I`m calling it that as it is shaped like a coil and has a resistance). Three resistors adjacent the coil look suspect too but checked out fine, well without a schematic all three had the same resistance value which was good enough for me. All capacitors looked fine but I haven`t ruled them out.



         I do know that most TV sets will refuse to power up if a short or other major problem is detected, sort of self preservation to the circuits. I removed the coil that`s situated in the white box as its pads were badly corroded and the board needed a deep clean with alcohol in this area. I cleaned the full board as there were small traces of damp in numerous locations, toothbrush and isopropyl alcohol till everything looked ok.



         I removed and re-soldered the coil to give it a good connection and hopefully solve any shorting/bad connections issues to cause these heat issues. Not really confident I had solved the issue I rebuilt the tele as I also fall foul of trying too many fixes at once and sometimes don`t know whats been successful. I used an air blower to clean everything up and tightened every ground screw on all the boards not just PSU. 




           I got a RED standby light instantly I plugged in.


          Held my breath and the Power Button and got the GREEN light with onscreen prompts. Is it fixed? I hope so. I switched it OFF and ON multiple times, unplugged it for 10 mins and re-plugged power to start,  without issues. Tonight I plan to unplug it and try a cold start tomorrow. Hopefully this TV has a new life. There can be many reasons why this plasma refuses to switch on, bad capacitors, bad FAN 6755 IC after a power surge, lightning or power cut. Other boards bad, pretty much endless reasons that YouTube and Google will saturate your viewing history with. Hopefully I just got lucky on this.