I have a magnavox 37MF321D/37 and the power wont stay on, just flashes. Replaced the IR sensor, still same thing.

SOURCE: Magnavox 37MF321D/37

1. Try this - hold the menu button down for 10 seconds. TV should power up; you will have to turn off front panel buttons on menu.

2. You can also try plugging in the TV through the USB on its panel to a computer or USB charger, and it may work. However, this is only a temporary solution.

3. Powering down the set or putting it in standby may have allowed the power supply to cool. Weak capacitors often go out of spec when they cool, thus preventing a section of the power supply from firing up properly again. There is a simple trick...just warm the back of the TV with a hair dryer for 5-7 mins after you have unplugged the TV. Look for the little areas of holes in the back panel of TV. Use these as your guide at where to use the hairdryer, but don't hold the dryer too close (say 5-6inches away). (Make sure the dryer is on High heat). If the TV doesn't turn on after you have heated it up (like it tries to come on but then turns off) you need to unplug the TV again, this resets it. And repeat those steps till it works. Resetting the TV after it fails to turn on is the key. Also, just leave the TV on. Don't turn in off. Since it is LCD, it doesn't take much power...only a few bucks extra a month for your utility bill.

4. A circuit board may crack about some of the larger components mounted on it. You can inspect the PCB's for fractures, and then repair them. It may also be poor soldering that has failed. I would be checking for these things first.

5. If you want to go in for a long term solution, you can easily replace the whole power board or just change the faulty capacitors. You will have to open the back panel and take a look. You can make out which are faulty, because their caps will be swollen on top. Here's a sample pic (not same model):

Check the specifications of the faulty capacitors, and get the replacements from your local electronics shop. If you are comfortable with this, you can use a pair of needle nose pliers to G-E-N-T-L-Y pull out the defunct capacitors. Once that is done, solder in the new capacitors carefully. If are unsure how to do this, try to get a friend who knows how to do this kinda stuff do it for you, or get a qualified technician. Warning: If you do not have a background in electronics repair, or are inexperienced, get a qualified technician to do it for you.

REMEMBER there are very dangerous voltages inside a TV that can KILL. Be sure to work SAFE when dealing with electricity. DISCONNECT THE POWER BEFORE YOU DO ANYTHING.

Hope that helps!

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SOURCE: My magnavox 37mf321d 37 LCD tv

This is a bad power supply and an easy fix. Their are several electrolytic capacitors on the power supply. If one is bad it will have a bulge on the top. Mine had a bad 2200uF and a bad 1200uF capacitor. About $7 worth of parts at Radio Shack. Radio Shack had the 2200uF but it was axial leads instead of radial. (leads come out of each end instead of one end) but It will still fit. They only had a 1000uf capacitor so I combined that with a 220uF capacitor and wired them in parallel. Make sure you put them in with the correct polarity.

SOURCE: How do i replace a 2200uf 50v

Remove the old one and install the new one./

SOURCE: Magnavox 37MF321D/37 flicking on & off

Sounds like you need to repair the power supply, don't fret, it can be really easy.  Here is a pair of youtube videos I made after following some advice on this website from other posters:

http://www.youtube.com/watch?v=qSS6ycUxS98

http://www.youtube.com/watch?v=oTOkHKPJsnM