Magnavox 50 mf231d37

[ljintexas]

Is this indicative of a failed panel?

Thanks

[MagicSmoke]

Re: Magnavox 50 mf231d37

Could be a lower scan buffer board or a bad connection on ribbon cable.

Did you have it apart or did the fault occur while viewing?

[ljintexas]

Re: Magnavox 50 mf231d37

Occurred while viewing..Thinking of buying it on the cheap and repairing..but Magnavox is not a real popular brand...

[ljintexas]

Re: Magnavox 50 mf231d37

I have it on the bench now. Will send pics of all boards soon...will check all ribbon cable connections first. Was a wall hanger in a pool room. Was not a gradual thing..went from working fine one day to this condition next day.
TIA

[ljintexas]

Re: Magnavox 50 mf231d37

I have it on the bench now. Will send pics of all boards soon...will check all ribbon cable connections first. Was a wall hanger in a pool room. Was not a gradual thing..went from working fine one day to this condition next day.
TIA

[ljintexas]

Re: Magnavox 50 mf231d37

I unplugged and reseated all six ribbon cables on the upper and lower buffer boards. I do see one 3300uf 10v cap that is pregnant on the p/s board.
Powered up, still same symptom. Did not see anything physically wrong with lower buffer board except maybe a little corrosion on surface mount resistors.
Should I look to any components on lower board?

Thanks

LJ

[MagicSmoke]

Re: Magnavox 50 mf231d37

Damn looks like it's got a Samsung panel in it. These are known to have ribbon failures.

Look at the very bottom boards (scan buffers) that run across the panel. They are partially covered by the chassis. There are ribbons on those that have a chip on them that goes bad.

You may have to remove that part of chassis to access them for inspection.

[ljintexas]

Re: Magnavox 50 mf231d37

So the ribbon cables have a chip on them that goes bad? Are they readily available? All the boards say samsung on them. I will have to partially disassemble the chassis to get to the boards in the bottom. I am going to remove power board anyway to replace the bad 3300 cap. That should make chassis dis assembly a little easier. Anything in particular to watch out for?

[MagicSmoke]

Re: Magnavox 50 mf231d37

Unfortunately if one of them is bad they are not replaceable. Be gentle when taking them out and reinstalling.

The scan buffer could be the problem or the ribbon connection. BUT be extra careful when removing / reinstalling the heat shield over the boards if it has one. Don't pry on it with any thing.

There are foam pads on most I think that hold the chip on the ribbon to the chassis for a heat sink.

It just occurred to me to ask if anything was spilled on the front or if too much cleaning spray might have run down into it?

[ljintexas]

Re: Magnavox 50 mf231d37

There are no signs pf liquid on the screen/frame. I will be dis assembling it Sunday. On the road again!

[ljintexas]

Re: Magnavox 50 mf231d37

I could not see any chips that are part of ribbon cables. I did find a loose connector on the tuner interface board..Jack is labeled 1M36 in the picture. Is it possible that the bulging 3300uf cap on the power supply board could be causing this? I am going to replace it anyway this afternoon..after securing the loose connector, I now have light snow in the section that was total black before..but the line still exists. I also opened and relatched both ends of all ribbon cables. Visibly, all caps on lowscan board are okay. No pregnant ones...

Thanks for your help.

LJ

[MagicSmoke]

Re: Magnavox 50 mf231d37

In the 2nd pic board labeled F connects to other boards along bottom. That's where the ribbons are that have the chip on them.

They will be under the metal bracket. And yes to changing all but the large caps on PSU.

It's possible that one of the caps on the bottom board may be bad and not show it. They don't have to bulge or leak to be bad

[ljintexas]

Re: Magnavox 50 mf231d37

Do I have to take them out of circuit to test the caps or will I be able to see a radically different reading on a bad one in circuit? Can I visibly inspect the ribbon cables with chips or what do you suggest? I am going to replace bad 3300 cap on ps board before I uncover lower boards again. Thanks for your help.

[MagicSmoke]

Re: Magnavox 50 mf231d37

Unless you have a meter that can test them in circuit they will have to be removed to check UF and ESR.

Only if one is shorted internally will you get a ohm reading on meter. To test properly you need a good ESR meter.

[ljintexas]

Re: Magnavox 50 mf231d37

I have several fluke meters with capacitance on them..measure nano and picoferads..In circuit, they all seem to charge and discharge. Here are the ribbons in all their glory. all look pristine. I looked at them closely. I reseated all of them. Will replace bad cap on ps board next.

[ljintexas]

Re: Magnavox 50 mf231d37

Do I need a meter other than the flukes that I have? They both measure Meg-ohms and capacitance up to 10000uf with auto-ranging or I can manually set the range.

Thanks for all of your advice and help.

LJ

[ljintexas]

Re: Magnavox 50 mf231d37

Replaced two 3300uf caps on ps board. Still have the same malady. I am inclined to think that the E buffer board has an issue.

[ljintexas]

Re: Magnavox 50 mf231d37

Gambled $20 on an E buffer board. If that is not it, then panel is junk as it means chip on ribbon cable is bad.

Thanks

[MagicSmoke]

Re: Magnavox 50 mf231d37

It slipped my mind because I did not see it in pics the first time, But the logic board could also cause this.

In a dark room can you tell if that part of panel has any glow or luminescence, sparklies?

Edit... just reread thread and you indicated there is activity in the dark area. So if buffer doesn't fix it then logic board is suspect.

[ljintexas]

Re: Magnavox 50 mf231d37

It has sparklies in the black region now. Did not before I replaced the caps on PS board.