magnavox tv has no picture or sound

Discussion in 'General Electronics Chat' started by momofthree, Nov 5, 2008.

  1. momofthree

    momofthree Thread Starter New Member

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    After working fine a few hours ago, our magnavox tv will not display a picture. When the "power" button is pressed the tv will make the clicking sound that, in the past, as indicated that it is on. However, there is no sound or picture. The cable modem displays that power is available there. We have unplugged and plugged the unit to no avail. Any suggestions or diagnosis would be great! Thanks.
  2. SgtWookie

    SgtWookie Expert

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    Welcome to the Forums.

    How old is your Magnavox TV?

    If it's getting close to 7 years or more old, it's probably not worth getting it repaired.

    Since you hear the "click", that's enough evidence for me to indicate the set has power to at least the standby circuits. There are a number of protection circuits in the set that will shut it down if a fault is detected, such as voltage levels that could result in X-ray emissions.

    TV's can easily become damaged if there are voltage "spikes" on your household AC voltage supply.

    I do not recommend opening the case of the TV, unless you're an experienced technician. Even weeks after power has been removed, very high voltages may still be present; 14kV to 20kV. Accidental contact with such voltage levels can be lethal.

    Even LCD TV's have lethal voltage levels to drive the CCFL lamps (cold cathode flourescent).
  3. momofthree

    momofthree Thread Starter New Member

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    Thanks for the response. The tv is about 3 years old. Do you think it would be worth getting repaired?
  4. theamber

    theamber Active Member

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    I will tell you a rule of thumb about something being worth repairing;
    First it does not matter how old is it unless the CRT shows burned or the picture being washed out.
    Second look at how much it will cost the repair versus replacing it by a new one.
    Third most repairs should carry a 3 months guaranty.

    Now, your TV is energizing the relay (that is the clicking sound) as it was said it could be the 'high voltage shut down' circuit that is activating the power shut down or the HVSD could be ativated by an overload some where in the power supply or the HV horizontal if it is a CRT type. If you don't have the schematic is going to be guessing. You should get a free estimate from a repair shop.

    The highest CCFL inverter supply that I have seen it had 830 Volts, the big majority are around 350 V.
  5. momofthree

    momofthree Thread Starter New Member

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    Wow, what wonderful people are here. The only electronics exposure I have had is high school physics! Thanks for all of the advice.
  6. Audioguru

    Audioguru New Member

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    Magnavox is Philips. Their TVs are made in China now like all the others.
    Today you can buy a CRT TV for almost nothing.
  7. SgtWookie

    SgtWookie Expert

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    Sorry I didn't get back to you sooner.

    If it's only three years old, it may be worth having it repaired, particularly if it's HDTV capable.

    It depends upon how much damage was done when it stopped working.

    Sometimes, the damage is limited to a couple of inexpensive components. The expense is then mainly the time it takes for the technician to find and replace the parts. While all televisions perform similar functions, the internal designs are quite different.

    Stiff competition has forced manufacturers to design most consumer products to be produced as cheaply as possible; most shoppers will choose the least expensive product that has the features that they need. This often results in products that don't have as long of a lifespan as otherwise might be achieved.

    You can still buy high-quality, long-life products, but they're very expensive, as they are not produced en mass; as the vast majority can't afford them.

    But I'm rambling - sorry 'bout that.

    Ask your friends for recommendations on local TV repair shops.

    If you have cable or satellite TV, call the cable/satellite TV company and inquire if your cable/satellite has been cut off.

    Take the set to the shop. Having a technician visit the house nowadays is no longer affordable, if you can even find someone who will do that. Ask for a quote before repairs are made.

    Some components are quite expensive, like the flyback transformer. If the flyback transformer needs replacement, just the part itself frequently costs over $100 (not including installation) - and then you'll have a 3-year-old TV that might last another 3-4 years.

    These kinds of things are pretty difficult to diagnose via the Internet.

    However, I had something similar happen to one of our TV's.

    We have a 32" Zenith that's a few years old. One day, it suddenly went from working just fine to no sound, no picture, and an odd "snap" sound coming from the set every few seconds. After purchasing a Sam's Photofact online and downloading it, I determined that a Zener diode had shorted out, causing a resistor in the protective circuit to get burned up. I replaced both the Zener diode and the resistor, and the TV has been working just fine for the last two years.

    But your story may be completely different. I am not suggesting that you attempt to diagnose the set yourself; you need proper training and experience to do that.

    In the meantime, while the TV set is in the shop, take the kids down to the public library. Get them reading.

    TV is highly overrated.
  8. momofthree

    momofthree Thread Starter New Member

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    Thanks, SgtWookie!

    I enjoy your insight. If there was not a weather channel addict in the house, we could probably do without. It has now been 4 days, and no one has missed it yet! Thanks again for your time.
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