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2015-10-23

Philips 42pf9966 Plasma 2004 model - defect 100µ capacitor in standby power supply.

A little mouse can demobilize an elephant.

A friend presented a 2004 Philips plasma TV to me. The device would begin booting but once the relais clicked it switched itself off.

This is a BIG machine. Enormously heavy. The level of component integration just wasn't as high as today. Many boards with discrete circuits around. Even DC-DC converters, which come in chips today, were built with transistors.

It already has Ambilight - implemented with CCFL tubes, not with LEDs like modern models! Amazing.

It once cost 4500€ - not for very long though.


It had no stand and I didn't want to carry this monster into my lab, so I did some checks on it at my friend's place. Something had to be wrong with the power supply. It did not start all the voltages and switched off after 5sec or so.

I decided to pull out the supply for measuring in my lab. The excellent service manual was easy to find at elektrotanya. Wow, this is the biggest power supply I've ever seen!


I tried to figure out how to start it. In modern supplies this would be a simple connection to the power-good pin from STDBY or ground. Not here. This one produces three different standby voltages, which are partially looped through the main board and come back as OK-signals to the supply. It has multiple stages, which activate in a certain sequence controlled by individual signals.

I gave up on that and started to measure all the standby voltages instead. 3.3V, 5.2V were ok. But the supposed 9V were only 6.1V! I tracked down the smoothing cap. It was just a little 100µF SMD type.


I checked the voltage with my scope and the problem was clear: a 6V baseline and way too high spikes up to 9V. This cap wasn't doing its job. I removed it and it measured only 85µF. Dead alright! I soldered in a new one quickly and the voltage measured proper 9.5V.


Board back in the TV and it started just fine. Nice. As little as 1€ material bill this time.

This little sucker made all the difference in this enormously complex machine:


Philips used to be top of the notch. This plasma monster proves it. It is an engineering masterpiece, which flawlessly ran for over 10 years. These days Philips TVs don't stand out from the crowd. They are not even built by Philips anymore.

6 comments:

  1. Hermann, you are a hero!
    I have a 42pf9967 (more or less its successor) which featured the exact same faulty smd micro elco. Easy replacement and this masterpiece of dense material and thorough engineering is back on its feet again!

    Greets from Holland,

    Elwin de Jong

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    Replies
    1. Thanks! Great to see that my repair adventures help other people fix their stuff :-)

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    2. Hi
      I know this is an ancient post but have same problem with my same model plasma. What exact capacitor did you put in to replace the old and one

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    3. Any low ESR type will do. A good brand like Nichicon, Rubycon or Panasonic.

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  2. Wow. Thanks for the post . Hunt for long enough and the internet and google will deliver. In this case both a hint as to where the problem may lie and where to access the manual.

    Mine has no standby led, but will switch on, after two tries, with a blue led. There is no picture or audio . There is a faint noise from the soundbar at the bottom , maybe fans, or the speakers.

    I've found I hope a retired technologist who can find the actual fault on mine. The board will have to be taken there today or tomorrow; after that we have a Covid lockdown here in Cape Town and South Africa.

    Regards

    Paul Fanner

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  3. Still relevant! Thanks do much, that saved mother in law's plasma!

    Best regards
    Christian

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