Magnavox 46ME313V/F7 LCD shuts off immediately after displaying splash screen

[SurrealMustard]

I'm working on this cheapo Magnavox LCD, and I was wondering if anybody had any troubleshooting pointers. What happens is that when anyone tries to turn it on, the red light blinks, the screen turns on, and the splash screen appears, but then it turns off. Nothing looks obviously bad on the power supply board or mainboard. Any ideas?

[cyricdark]

Re: Magnavox 46ME313V/F7 LCD shuts off immediately after displaying splash screen

I had the exact same problem with an 50" emerson that uses same pcb board (BA4GU5G0201 3), after trying power board from another set, and disassembling the screen to check for bad leds I took a chance and ordered in a mainboard from a 40" magnavox that looked the same and had the same pcb model number, same plugs, etc just different part number on the stickers for 20$ on ebay(the right board was 70$ which was more than i was willing to spend) and other than needing a magnavox remote control now it worked great. So I'd say your problem is mainboard also.

[SurrealMustard]

The quest for cheaper repairs

I had the exact same problem with an 50" emerson that uses same pcb board (BA4GU5G0201 3), after trying power board from another set, and disassembling the screen to check for bad leds I took a chance and ordered in a mainboard from a 40" magnavox that looked the same and had the same pcb model number, same plugs, etc just different part number on the stickers for 20$ on ebay(the right board was 70$ which was more than i was willing to spend) and other than needing a magnavox remote control now it worked great. So I'd say your problem is mainboard also.

Thanks for following up. That's what I ended up assuming based on the symptoms and the vast presence of mainboard repair kits on eBay. Against my better judgement, I sprung for the overpriced $70 board online and it was totally dead. Are there any of those $20 units left that you found?

[petehall347]

Re: Magnavox 46ME313V/F7 LCD shuts off immediately after displaying splash screen

you would be better seeing what is putting it into protection and shutting it down .
it could be almost anything if indeed is protecting itself .might just be a bad solder joint maybe not . few voltage checks should get you on the way if you are up for that sort of thing ?
most likely a capacitor not charging fast enough because its no longer good .
voltage checks should be a big help . no use guessing unless its a well proven fault with a certain board

[SurrealMustard]

just a little progress...

After finally getting a working board, I'm having slightly better luck with this thing, but not much. It now boots past the splash screen and shows the channel number in the corner, but then immediately shuts off after that.

I get a fairly low-res Emerson emblem followed by the channel number in the corner before it calls things quits. Any ideas as to what else might be ailing this sorry thing?

[SurrealMustard]

Still nothing

Any new ideas? Could a power supply or bad lamps be causing this kind of failure? Or is it possible that I ended up with another bad mainboard?

[CapLeaker]

Re: Magnavox 46ME313V/F7 LCD shuts off immediately after displaying splash screen

Check the protect jumpers on the PSU working vs after shut down.

[SurrealMustard]

Looking for protection jumpers

Check the protect jumpers on the PSU working vs after shut down.

Where would those be located?

[SurrealMustard]

Try something new!

I guess I'll try looking for a power supply and see if it works any better with that.

[budm]

Re: Looking for protection jumpers

Where would those be located?

PROTECT1, PROTECT2... printed right next to the jumpers on that power supply board.

[SurrealMustard]

Found!

PROTECT1, PROTECT2... printed right next to the jumpers on that power supply board.

Ah, I found one of them. What exactly am I looking for on it?

[Andrew F. Ali]

Re: Magnavox 46ME313V/F7 LCD shuts off immediately after displaying splash screen

Check the DC voltage....I suspect a Backlight fault, though

[budm]

Re: Magnavox 46ME313V/F7 LCD shuts off immediately after displaying splash screen

Check the DCV on those jumpers when TV is OFF, black probe on chassis and leave the red probe on one of the jumper and turn on the TV and see what you get then wait a few seconds to see if reading changes, do the same for another PROTECT jumper.

[SurrealMustard]

Results!

Check the DCV on those jumpers when TV is OFF, black probe on chassis and leave the red probe on one of the jumper and turn on the TV and see what you get then wait a few seconds to see if reading changes, do the same for another PROTECT jumper.

PROTECT3 measures .4volt after the power button is pressed before it starts booting up.
PROTECT3 measures .1volt while it is booting up and displaying the splash screen, then jumps to .5volt (or so) for a fraction of a second as it shuts off. After the television shuts off, PROTECT3 drops to zero.
PROTECT1 registers absolutely nothing at any time.
Is that normal behavior?

Check the DC voltage....I suspect a Backlight fault, though

Is there any easy way to test for that short of dismantling the entire panel?

[SurrealMustard]

best way forward?

If it makes any difference, I tested this with the backlights disconnected and got the same symptoms, (sans backlights, of course) if that makes any difference.

Based on these findings and the aforementioned measurements, what would be the best way forward with this? Just dive in and check the backlights?

[CapLeaker]

Re: Magnavox 46ME313V/F7 LCD shuts off immediately after displaying splash screen

if you want you can connect the back lights to the PSU, fire the PSU up and measure the DC voltage of each back light string. Other than that, you are on the correct way to check the back lights.

[SurrealMustard]

Tested lamps.

Well, I finally broke down and tore this thing apart. Turns out that there is some kind of issue with backlights not lighting up. The weird thing, however, is that after testing each lamp in the middle row individually with the multimeter, I found that they all light up and work. Does this mean that I've got a bad power supply?

[CapLeaker]

Re: Magnavox 46ME313V/F7 LCD shuts off immediately after displaying splash screen

again, fire the PSU up and measure the DC voltage of each back light string on the connector at the PSU with the LED's connected.

[SurrealMustard]

No voltage at middle string

again, fire the PSU up and measure the DC voltage of each back light string on the connector at the PSU with the LED's connected.

Now we might be on to something. The first string measured 47-52 volts, the third string measured within a couple volts of that, but the middle string measured pretty much nothing. What could this mean?

[CapLeaker]

Re: Magnavox 46ME313V/F7 LCD shuts off immediately after displaying splash screen

On this TV PSU, each string has its own control ic, etc. IC1301, IC1201 and IC1101. Each has its own circuitry to control one string each. Now you have to find out which circuit isn't working. I am guessing the one with IC1201 since it is the middle one, but you have to verify that.
What part numbers does IC1201, Q1201 and Q1202 have? Check D1202 Q1201 and Q1202 for a short.