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Tim Nolan
Tim Nolan, TV Repair Technician
Category: TV
Satisfied Customers: 19454
Experience:  Factory trained TV repair technician. U.S. NAVY trained.
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Ok the Magnavox 42MF439B TV I have worked for about 2 hours

Resolved Question:

Ok the Magnavox 42MF439B TV I have worked for about 2 hours and then it shut off. Now when I power it on the green LED flashes and then goes out. The TV shuts down. What is causing this?
Submitted: 2 years ago.
Category: TV
Expert:  Tim Nolan replied 2 years ago.

Hi! Thank you for using Just Answer today! My name isXXXXX am happy to help you with this! Please bear with me and be patient as sometimes these issues take a little bit of figuring out before we know what's wrong. If you could give me some more information it will be very helpful:

-Does the light flash a pattern? (example 6 blinks pause 6 blinks pause repeat)
-How old is the unit?


Please give me this information and I will be happy to assist you further.
Thank you,
Tim Nolan
Customer: replied 2 years ago.

Tim

I could not tell you if the light flashed a pattern because I can't get it out of standby mode again.

The TV is about 2 years old. Manufactured DEC 2009

Expert:  Tim Nolan replied 2 years ago.

There are a couple of things that could cause this, unfortunately there is no reset for this television other than unplugging it. It will have an internal failure at this point. I will try to explain the possibilities the best I can.


First, we have seen some capacitors fail in your model and cause funky problems like this. If this is the case you could be looking at somewhere around $175-$200 to fix the set.


Next could be an inverter, this would not be good news because you could be looking at $200-$300 for the repair.


Lastly you could have a problem with the panel itself, this would mean a new set for sure because the part cost is more than a new set. The panel in your tv is about $800 just for the part.


Any of these could cause your problem, but it will require troubleshooting to determine the exact cause of your problem. If you have experience, and test equipment and would like to attempt some troubleshooting I will be happy to assist you, however if you do not have equipment or experience then you would need a repairman at this time to get an exact diagnosis. I am sorry that I don't have a quick fix or easy answer for you on this one, it is definitely an internal failure.



If you would like any additional information or have more questions please don't hesitate to ask!


Please remember to press the ACCEPT button when we are finished, it is the only way I can get credit for helping you. I want you to be 100% satisfied so please, by all means ask any questions you might have on this subject. Positive feedback is always appreciated.


Thank you,
Tim Nolan
Customer: replied 2 years ago.
I have 20 years experience repairing computers. How much different is it to repairing a TV? I have a digital multimeter. What else would I need to troubleshoot the problem.
Expert:  Tim Nolan replied 2 years ago.
Its not much different, as long as you can test voltages we should have no problem troubleshooting it.

What you need to do first is remove the back cover and inspect the power supply for any capacitors that have bubbled tops. Let me know what you find....If you are unsure what you are looking for you can post a picture to me and I will inspect for you. (if you can post a picture, please click the icon above where you are typing with the paper clip on it. This will allow you to upload a picture)

Customer: replied 2 years ago.
There are no bubbled capacitors that I can see.
Expert:  Tim Nolan replied 2 years ago.
OK I need to know what the DC voltages are coming out of the power supply.

If you can get me a picture of the tv with the back off, I can mark on it what I need. (if you can post a picture, please click the icon above, where you are typing, of the paper clip. This will allow you to upload a picture)


Tim

Customer: replied 2 years ago.
Here are two pictures.graphicgraphic
Customer: replied 2 years ago.
Are you still there?
Expert:  Tim Nolan replied 2 years ago.
OK I need all the DC voltages on those diodes. You can use any of the metal on the back of the panel as ground, like where I put the blue boxes.

Tim

graphic
Customer: replied 2 years ago.

Tim

here they are

00.0

00.2

00.1

00.1

00.4

00.4

02.2

02.2

00.7

00.7

00.7

Expert:  Tim Nolan replied 2 years ago.
Check them now when you push the power button, any change?

Tim
Customer: replied 2 years ago.

Tim

There is no change in voltage.

Expert:  Tim Nolan replied 2 years ago.
OK somethings not right, if the green light on the front is flashing we must have voltage of at least 3 or 5 volts on one of those diodes.

Tim
Customer: replied 2 years ago.

Tim

After I took the back off I could not get the green light to flash.

Expert:  Tim Nolan replied 2 years ago.
When you plug it in does the light on the front come on at all?

Tim
Customer: replied 2 years ago.
only the red light is on. Have try to get the green one to light up but nothing has worked.
Expert:  Tim Nolan replied 2 years ago.
OK well even with that...if the red light is on we should have minimum 3.3v or 5v somewhere. You are checking DC right?

Tim
Customer: replied 2 years ago.

Well I have checked it again and this time I got the following.

00.8

00.1

00.8

02.8

00.4

00.4

02.2

02.2

00.7

00.7

00.7

Expert:  Tim Nolan replied 2 years ago.
You are on DC right?

Tim
Customer: replied 2 years ago.
Yes
Expert:  Tim Nolan replied 2 years ago.
Put your meter on resistance and touch your leads together, how many ohms do they read


Also, if I don't respond right away, I may lose power...this tropical storm is hitting right now and some areas are losing power.

Tim
Customer: replied 2 years ago.
00.0
Expert:  Tim Nolan replied 2 years ago.
See the wires going down to the circuit board with the light on it...check the dc voltage on those wires.

Tim
Customer: replied 2 years ago.
I'm getting 01.7 - 03.2
Expert:  Tim Nolan replied 2 years ago.
OK there is our 3.3 that we are looking for. Does the 3.3 change at all when you push the power button?

Tim
Customer: replied 2 years ago.
Yes it goes to 00.0
Expert:  Tim Nolan replied 2 years ago.
But you get no other reaction from the tv at all? (no relay click?)

Tim
Customer: replied 2 years ago.
no
Expert:  Tim Nolan replied 2 years ago.
Are there more than one 3.3v line going to that front board?

Does the red light go off for a second when you hit the power button?

Tim
Customer: replied 2 years ago.

there are 8 pins. here are the readings: 00.0, 03.2, 00.0, 01.7, 00.0, 03.2, 00.0, 00.0

when I push the power the readings: 00.0, 03.2, 00.0, 01.7, 00.0, 00.0, 00.0, 00.0

At the board I'm getting readings: 00.0, 03.2, 03.2, 01.7, 00.0, 03.2, 00.0, 00.0

when I push the power the readings: 00.0, 03.2, 03.2, 01.7, 00.0, 00.0, 00.0, 00.0

Expert:  Tim Nolan replied 2 years ago.
Ok then it would appear we have a bad main board here. This it that green board under the metal cover there with the HDMI input on it.


A91H6MMA-003 is the part number you need, it runs about $100. I would recommend www.encompassparts.com.

Tim

Tim Nolan, TV Repair Technician
Category: TV
Satisfied Customers: 19454
Experience: Factory trained TV repair technician. U.S. NAVY trained.
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