New TV Power Board

So I turned the TV on the other day to watch something – all good – walked away, came back and the TV was off.  Hmm, strange, so I tried to turn it back on but nothing.  The next day I pulled the back cover off to find two boards, one full of SMD parts (for the video logic) and the other full of large high voltage parts (the power supply).  I tested the fuse and it was blown so I swapped that for a new fuse.  I plugged it back in and was greeted with a flash of light.  I decided to dig a bit deeper and found the neutral and hot lines to be shorted somewhere.  There weren’t any visible shorts on the board so it must be a component.  I pulled the bridge rectifier off and the short still remained.

If you are familiar with switching power supplies then you know that the AC power first travels through a filter (consisting of inductors and/or capacitors) then it gets rectified to DC and filtered by a large capacitor.  After that the DC meets the switching element, which usually consists of a MOSFET which then connects to a transformer.  The MOSFET is the heart of the switching mode power supply and they usually have the supporting oscillator and comparator circuits built in to make them a complete SMPS package. These packages are sometimes hard to find when replacing failed components and if you can find them, they usually aren’t cheap.

About this time I started looking online for replacement power supply boards and to my surprise I found no less than 10 from various sellers.  Either this board fails very often or they were simply pulled from broken TVs during recycling.  In either case, I ordered one and 3 days later I had it installed and the TV working again.  The best part was that the replacement board (with free shipping) was less than $15 and saved me from buying a new TV.

 

The TV back together with new power supply board installed.  Its amazing how much empty space there is.

The TV back together with new power supply board installed. Its amazing how much empty space there is.

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