HELP!!! Magnavox 51" with no picture just sound

[casey]

I have a 51" screen t.v Magnavox with no , I have no idea about how to fix the t.v. so I need some guidance on how to fix it. Any ideas???

[arneson]

Re: HELP!!! Magnavox 51" with no picture just sound

I certainly have ideas about fixing big TV's.
First take off front large flat plastic.
Then climb inside and pretend to be Tom Cruise.

Ok, That was meant as a joke. The real advice is more of a question.
Are you capable of removing the circuit boards one by one for inspection and resoldering after you've checked for voltage at the test points around the power supply. Do you recognize the dangers of high voltage, I think I'm asking if you are a tech and if so do you have the repair manual for your 51 incher?

[casey]

Re: HELP!!! Magnavox 51" with no picture just sound

I am not a tech and I have means of testing the power however, I do not have the manual or anything I am just atleast trying to figure out what is wrong with it and trying to see if I could do it myself, I don't know much about this and I don't want to spend an arm and a leg doing it, if you know what I mean.

[arneson]

Re: HELP!!! Magnavox 51" with no picture just sound

I am not a tech and I have means of testing the power however

OK, I understand you have a voltmeter and I'll assume it's a multimeter.

I do love to discuss repairs of no picture big tv's and I have literally climbed into the front of some, but I did not sing karioky while in there.

No repair manual, but yes to user manual? The back section probably mentions , no picture, and I'm assuming it's the 51MP392H you are talking about.

To post a question such as yours, there is so much more information required to even consider an answer. I'll mention a few, Is it warrenty? Initial Symptoms? Is this a "Bar" set,( are you in the sports bar?) You know sometimes these are never turned off. I could go on, you get the idea.
I'm trying to be helpful.

[kc8adu]

Re: HELP!!! Magnavox 51" with no picture just sound

a year and chassis number would help.
there are so many things that can cause a no pic has sound that you will need the right tools to tell you what is working and what is not.
a decent dvm at minimum.

[Hagis2k]

Re: HELP!!! Magnavox 51" with no picture just sound

When you turn your set on can you feel any static electricity from the tube at all
to repair an unit without schematic over it it like walking out in the deep forest without
an compass/map try www.eservinfo.com search for the model/brand maybe you can find
it there...

Most common is bad solderings around the high voltage transformer and the surrounding components can lead to shorted H.O.T the transistor who "feeds" the
transformer one tip when you work with this kind of things keep one of your hands on your back ! otherwise you can lead the voltage/current thru you heart

Bad solderings come with the time the machine heats up cools down vibrations etc
sooner or later you will find cracks around the component legs/pads like an "o" but very faded

And magnavox can be an philips chassie to... search on the fcc id number

[kc8adu]

Re: HELP!!! Magnavox 51" with no picture just sound

magnavox is nap.
north american phillips.
btw projection sets have more protection stuff than your average direct view to keep from trashing the expensive crt's if you lose deflection.

[arneson]

Re: HELP!!! Magnavox 51" with no picture just sound

Yes and Shields Up Captain..
Sorry, had a startreck fart.

If it's the Model I mentioned they are not that old, that's why I asked about Warrenty.
The bitch is that the service should be done in house because it's like moving a piano to the shop and back.

[casey]

Re: HELP!!! Magnavox 51" with no picture just sound

I appreciate everyone's help, however, I found out that in order for me to get it fixed it would cost me about $450 and that is in the states, however, I am currently over in England and I know that there are few t.v. shops around here and they would charge me about £450 which is $900-1000 U.S. and that is how much I paid for the T.V. in the first place. To answer somones question, no it is not a bar t.v. I bought it and it is sitting in my living room right now and has been there, however i did move it from the US to England last year, but it has been working just fine. I did notice however, every now and then the picture seemed to jump to the left and/or right just a hair every now and then, but I didn't think anything of it. Is this a sign of something I shouldn't have ignored??? I also was wondering if there is anyone on this forum that may live in England willing to help me out. Let me know PM me or what not. If I can't get this fixed for a resonable price is there any parts of the t.v. that may be salvaged to use on other projects or anyone willing to buy some pieces of the t.v.??? Oh Yheaaa it is not warented and even if it was I couldn't get it anywhere to fix it.

[Hagis2k]

Re: HELP!!! Magnavox 51" with no picture just sound

I did notice however, every now and then the picture seemed to jump to the left and/or right just a hair every now and then, but I didn't think anything of it.

That sounds like an coldsoldering what i assume you can do if you have an
DMM and an solder iron remove the bigger transistors and meassure them i guess you have an short somewhere meassure diodes to i guess personly the H.O.T transistor close to the highvoltage transformer may be the problem but
also remember the windings of the "coils" inside the transformer can be bad so if you replace the transistor you may "blow it again"

How to check the transistors meassure all legs with the diod function on the multimeter meassure (b) to (c) (b) to (e) and (c) to (e) anode on the base meassure them in this order and swap the an meassure again pins you should found that it only leads in one direction some transistors have an internal damper diod between collector - emitter check an diagram over that component after that switch to resistance it shall be close to mega ohms between all legs

Check the diods the same way "red" test pin on one side and "black" on the other side (de solder one connection of the diod to) it shall only lead one way.

Also check for any burned resistors i had an problem my self with an luxor tv (swedish brand) that an 15r resistor that where an security resistor to the 8V supply voltage got burned it was feeding the microprocessor in the set it died
but no other errors i discovered that it was an design flaw the video/audio inputs where unbuffered :/

[mbates14]

Re: HELP!!! Magnavox 51" with no picture just sound

A chassis and model number would help.

lets assume its a PTV775. I have good experience with those.

loss of HV can result from missing vertical deflection, or bad HV out transistor.

the HV and horiz output circuits are seperate from one another. which means, you can have loss of horiz, and have HV, and vice versa. you can hear what "sounds" like HV, but not have HV. your hearing the horiz circuit running with no HV.

if thats the case, then the vertical circuit probably failed, or the HV out xistor is open. if its shorted, the set wouldnt start.