Magnavox 42" LCD no Power

[Dgtech]

Re: Magnavox 42" LCD no Power

Hi I'm new in here so please bear with me. I have a 42" Magnavox LCD model 42mf521d/37. The TV has no lights no anything. I replaced 4 blown caps on the power supply they were 1500uf. When that didn't work I replaced the 47uf and 3 100uf still no power. I have check the fuse and it seems fine. If anybody can see anything more I might try please all help is appreciated.

Since I now have the same board with the original caps in it, I'd recheck the values on the 4 blown caps that you replaced as I have found only one of them to be a 1500uF 25V cap. On the picture below I will notate which of these are which values.

[jbpest]

Re: Magnavox 42" LCD no Power

What was the location of the 2200uf 25v. I had 4 1500uf 25v on this board or so I thought.

[jbpest]

Re: Magnavox 42" LCD no Power

I replaced all the caps with 1500uf 35v. The one lone cap 2200uf 25v is at 2074. I may have bought the wrong cap for that positions.

[Dgtech]

Re: Magnavox 42" LCD no Power

The height and width of these four caps are similar as one value is not. It would have been easy to make that mistake. I barely caught it myself. The diameter of the 2200 is just slightly larger. Installing a 1500 in place of a 2200 might just be enough of a change to this circuit to keep it from powering up. If this is the cause of it not coming on, whew... what would be the chances that I'd get the same set within the same time you'd be working on it.

Badcaps.net rocks!

[Dgtech]

Re: Magnavox 42" LCD no Power

Since I now have the same board with the original caps in it, I'd recheck the values on the 4 blown caps that you replaced as I have found only one of them to be a 1500uF 25V cap. On the picture below I will notate which of these are which values.

Damn. I messed up in what I said in this post quote but the picture is correct.

3 X 1500 35V
1 X 2200 25V

[jbpest]

Re: Magnavox 42" LCD no Power

The fact you got the same board in and are in the same forum helping me its a Blessing from God. I must be living right. I've ordered the 2200uf and should have it in in a few days. Thank you

[Dgtech]

Re: Magnavox 42" LCD no Power

Hey JB, I need a favor from you. When I bought mine, it didnt have the speaker bar attatchment on the bottom. Could you post the model number for it? I'm having a hard time trying to locate one using the set model number. Once I have the part number or model number, I'll be able to look it up on ebay or something.

By the way, the set works fine now after recap, got picture, I just notice there was no sound, lol. DUH!! Speakers.

[jbpest]

Re: Magnavox 42" LCD no Power

I can't find the part number but I think this one on ebay will work.
http://cgi.ebay.com/Speaker-bar-Magn...item3f04b63b16

[Dgtech]

Re: Magnavox 42" LCD no Power

Thanks for that info. I asked him the question about this speaker and he responded with this "There is no model number stamped on it it does have 5 screw holes on it and is 40 7/8 inches long.". Does this resemble yours, If so, I will buy this from him.

[jbpest]

Re: Magnavox 42" LCD no Power

Yes, thats the same as mine and with 5 mounting holes.

[jbpest]

Re: Magnavox 42" LCD no Power

Ok, I got the 2200uf 25v in and installed. I still have no power at the on off switch and 2074 to ground is still reading 16 even with the new cap.

[Dgtech]

Re: Magnavox 42" LCD no Power

How about the inverter boards? Post some pics of both of them, master and slave.

[jbpest]

Re: Magnavox 42" LCD no Power

I'll get the inverter pictures hopeful later today but first when I removed the glue this cap was disconnected. I tried to reconnect it where I thought it goes but I'm not sure I put it to the right pin. These are the pics of the cap and the schematic for the position. It was still connected to pins 7and 8 I reconnected it to pin 5 but it could have been pin 6. I can't tell

[jbpest]

Re: Magnavox 42" LCD no Power

Here are pictures of the inverter boards.

[jbpest]

Re: Magnavox 42" LCD no Power

More pics of the cap on the scaler board.



Again this cap was loose and I put it back but it could be the wrong pin not sure. 7 and 8 are correct but not sure about 5 or should it have been 6.

[jbpest]

Re: Magnavox 42" LCD no Power

Hey did I lose you guys? I have been checking the power supply and I get some funny reading from what I can tell. I think my problem is there but I don't think its a cap.

[Jon B]

Re: Magnavox 42" LCD no Power

Check the small diode labeled 6079 on the board, it is located at the top left of the circuit board near the 2074 capacitor.

[jbpest]

Re: Magnavox 42" LCD no Power

I get the same ohms no mater which end I put the pos and neg. I think you talking about 6075 I can't find and 6079. With the diode checker on the dmm I get a 698 reading.

[digitalguy99]

Re: Magnavox 42" LCD no Power

I have the same TV, but a slightly different problem. When I try to turn on my tv, the green power indicator light flashes, as well as the backlight, but it never comes fully on. I have checked/replaced the capacitors and it made no difference. Is there anything else that could be causing this? Thanks in advance for any help I can get regarding this issue.

[retiredcaps]

Re: Magnavox 42" LCD no Power

I have the same TV, but a slightly different problem. When I try to turn on my tv, the green power indicator light flashes, as well as the backlight, but it never comes fully on. I have checked/replaced the capacitors and it made no difference. Is there anything else that could be causing this? Thanks in advance for any help I can get regarding this issue.

1) Hookup a dvd player with a movie playing to your TV so that you have sound.

2) Now shine a flashlight on the screen.

3) If you see the image of the dvd movie and your TV inverter board looks like the one posted in post 34, then measure the resistance (with power off and lcd unplugged) on the secondary transformer pins as per

http://lcdparts.net/TransformerDetai...ProductID=2732

That is, measure the resistance between S1 and S2. Do the same for S3 and S4. Set your multimeter to 2000 ohms, if manual ranging.

4) Report all ohms measurements for all transformers.

You should have 10 transformers and 2 readings each for a total of 20 measurements.

5) What brand and series of capacitors did you use for replacements? Where did the replacements go? On the power board? On the inverter board?

6) Please post clear focused pictures of your boards using the manage attachments features like the other people in this thread. Do not post inline.