Question about Toymax Magnavox 47MF437B 47 in. LCD TV
TV screen went totally black, chirping noises started. We could still hear the sound correctly but then it went garbled and then completely our other than chirping noises. TV did not respond to attempts to change the channel with remote but would turn off manually.
Could be main AV board not receiving the proper voltage due to a failing capacitor or power transistor. So I suspect a PSU failure.
Posted on Jan 16, 2013
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Posted on Jan 02, 2017
The TV was turn ON for the first time or the TV reboot/reset.
Universal remotes are not as "universal" as we like them to be. They only control a very, small amount of options for the TV.
You'll need the remote that came with the TV to fix this problem because it has the special RED, GREEN, YELLOW, and BLUE buttons you need.
If you don't have the original remote, you can get one at this web site. It's the best price going right now. $29.95
Posted on Jun 01, 2009
Probable failed power supply; switching power supplies can fail and produce this kind of noise.
My standard response is pasted below:
If it's failing to turn on, the main power supply is probably at fault and without some technical background and a couple of test instruments, you will not be able to do the repair yourself.
What you can do though is; unplug the set, let it stand overnight or at least several hours, remove the back panel and look for a separate board with mostly larger components on it; it will have a ferrite core (no laminations as with a line-frequency part) transformer on it and several larger capacitors which are cylindrical and mounted vertically to the board.
Before touching anything inside, especially on that board, allow several hours to be safe since the larger capacitors can hold a painful voltage charge for some hours.
If you see signs of overheating such as discoloration of the board material, the PSU may not be repairable but if you can find a part number on the board, you might be able to buy the power supply from the mfr. and install it yourself but it will likely have the same problem eventually unless they have altered the design or improved component quality.
If there are no signs of heat damage to the board, there may be companies offering to repair it as a subassembly instead of repairing the whole set which could be much more expensive.
If you choose to replace or have it done, the main power supply still may not be at fault since most are capable of switching on and off if a downstream problem is causing an overload
Posted on Nov 03, 2009
The problem can be in the backlight inverter board (hard to get to), or the main power supply module may not be working. Look at the power supply first since it is easy to get to, look for burnt parts, bad capacitors.
Posted on Nov 11, 2009
SOURCE: tv turns black after about
You may have power supply problem due to bad component or bad solder joints that expanded when warm up, or problem in the backlights inverter circuits, or bad T-CON board.
Try this when the screen black out.
First, look at the screen in darkened room to see if you can see any slight glow from the screen, if it does, then the problem can be the T-CON (not getting the 12vdc) or the main logic board not feeding the signals to the T-CON board.
if not, next place to check will be the power supply module, make sure it has 24vdc which is required by the backlight inverter to work, the reason for not having 24vdc can be from bad DC filter caps (leaking/bulging top, high ESR) or short circuits in the inverter board which will cause the 24vdc supply to go into shutdown mode, so you may have to disconnect the power cable that feed the inverter board to see if the 24vdc will work without the inverter board hookup, you will need to apply about 3~4 amp of load to the 24vdc to make sure it can handle that. There are fuses on the backlight inverter boards also. So there is some troubleshooting you will have to do to find out the causes of the problem you are having.
If you are going to DIY and have proper tools, electronics knowledge, and know safety precaution then please read on:
Basic LCD monitor and TV troubleshooting guide:
Failed TV and Monitors pictures: http://s807.photobucket.com/albums/yy352/budm
Learn about bad caps: http://en.wikipedia.org/wiki/Capacitor_plague
Capacitors kit: http://lcdalternatives.auctivacommerce.com/Default.aspx he can make you a set of caps.
Or www.digikey.com, just make sure to use caps with low ESR, 105c, high ripple current and long life rating such as PANASONIC FM or FC series.
Posted on May 01, 2011
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