Thursday, September 30, 2010

Do it yourself television repair hit by high voltage from power surge caused by lightening or Generator.

Do it yourself television repair hit by high voltage from power surge caused by lightening or Generator.

I have received several emails from my blog followers on how to go about with electronics items hit by power surges. Mostly they have a problem of getting a technician near them and others just want to try their hand in this fascinating career.

Therefore in this article I am going to discuss how you can handle this problem at the comfort of your house.

But first you need to be prepared to do some investment of the basic tool of the trade.

The minimum you should have include:-


Screw driver(flat/star)


These you can get them cheaply from your nearest electronics shop which I believe they are readily available.

After you have the tools now we are ready to start the job but before you open the equipment safety first.

First be very sure you have disconnected the machine from the power socket, I mean not just switching off the power via the power switch but removing the power cable completely from the socket.

I don’t advice you to do any voltage testing here unless you some basic training on safety precaution around the power supply in electronics equipment.

From my experience I have noticed that problems of power surge usually affect the primary power supply components, especially semiconductors and capacitors.

Failure mode of these components is either short or open so your meter should be set to low resistance range/diode test is even better here for short and high range over 20 K ohm for open.

Get a comfortable place/table and open the machine, keep note of how you open the equipment because when closing it up you would be doing exactly the opposite.

After opening the machine go straight to the power supply section, ie components between the inputs of the power supply and the main (switching) transformer.

First check the fuse with the meter on diode test- it should beep indicating the fuse is ok, if not consider the fuse gone.

Next measure the resistance of the surge limiter (white rectangular in shape) this too should read low ohms on the diode range.

Now if the fuse or the surge limiter is gone, DON’T REPLACE THEM.

Expect a big short ahead and the most likely culprit is the switching transistor or I.C usually the one you will find bolted to a heat sink. You can directly replace them without even measuring them.

There is also another small transistor near that big one, one can change it too, it is recommended because sometimes its goes and other times it can survive.

Continue Scanning the area looking for the main capacitor (biggish) rated 400volts for countries using 240 vac or 200 volt on countries using 110 VAC like USA.

If you find this main Capacitor has top silvery plate swollen, even a slight sign consider it bad. Also note if at the button of that capacitor there is some liquid oozing. If none of the above symptoms then consider the capacitor is ok for now.


From my experience changing those components always make the power supply to come up again.

If you don’t want to invest on the multimeter then you need to directly replace the components I have listed above: ie Main capacitor, chopper transistor, fuse, and surge limiter, diode/bridge are quite stable so you can leave them for now.


If you change them and still nothing happens then I advise you to take your machine to a trained technician


Note:

You can use this method to repair other electronics equipments using switch mode supply like DVDs, Monitors, etc so long as they have been hit by power surges.


Thanks you guys



Let meet in our next class

6 comments:

  1. HELLO HUMPHREY
    thanks for good article
    i learned too many things
    regards
    beh

    ReplyDelete
  2. Hi Beh, thank you for your comment: NEVER STOP LEARNING...

    Regards Humphrey

    ReplyDelete
  3. in my country fixing the tv in the house of costumer is easy technician just change all possible culprit component with out testing with ohm or voltmeter if set fixed is ok other wise they say you have to bring set to their office
    have good day
    beh

    ReplyDelete
  4. Thanks, would like to see something similar but for normal use heat damage like cold solders or damaged capacitors.

    ReplyDelete
  5. hi without a name, this was a special case, for other kind of failure mode there is no general rule to go about it. it all depends on the circuit involved and therefore no general rule.

    however sometimes if a component has catastrophic
    failure you can see with your eyes and change them and if it work out lucky you, same case to dry joint/crack on the circuit or component broken you can still replace them directly.

    Again for your safety don't do any voltage testing if you don't have basic knowledge on safety precaution around the electronics equipment...we need you around!

    Hope i have answered your question, any case of any other issue please drop me line on the email provided on my profile.

    Good day and take care

    Regards Humphrey

    ReplyDelete