Mangavox 50ME314V/F7 "Funai junk"

[budm]

Re: Mangavox 50ME314V/F7 "Funai junk"

Well, the schematic I provide is to be used as the guide only to see what the typical Voltages should be not the exact as how the Voltages are generated.
To me, that standby AL+3.3V should always be present with or without the main board connected since it is the standby Voltage after all.

[heavymachines]

Re: Mangavox 50ME314V/F7 "Funai junk"

Well, the schematic I provide is to be used as the guide only to see what the typical Voltages should be not the exact as how the Voltages are generated.
To me, that standby AL+3.3V should always be present with or without the main board connected since it is the standby Voltage after all.

That raises one big question however, how is this thing getting standby with main connected but not when disconnected, back feeding from somewhere?

[budm]

Re: Mangavox 50ME314V/F7 "Funai junk"

So I trace out the power supply board. This power supply board has 2 power supply sections.
Transformer T601 is for
AMP+13V (about 8V in standby, it will go up to full Voltage when PS-ON is present, D653/655 are the rectifiers for this 13V supply)
PO+21V (about 13V in standby, it will go up to full Voltage when PS-ON is present, D650 is the rectifier for this 21V)
The 3.3V regulator is on the Main board and is fed by the AMP+13V supply.
But since you did get full 13V and full 21V when you turn on the TV so that means the 13V & 21V power supplies are OK
I think you have the problem in the backlights circuit at this point and the BL-ON also seems low too.
Transformer T1701 is for the backlights LED power supply (D710, 711, 712 are for generating the 40V to feed the 3 boost converter circuits) for driving 3 LED strings (you can see 3 LED driver ICs and 6 power MOSFETs for 3 boost converters and 3 PWM controlled MOSFETs.
This is getting difficult due to no matching diagrams.

[kc8adu]

Re: Mangavox 50ME314V/F7 "Funai junk"

unplug power supply from main and check all the mlcc in the buck converters on the main for shorts or leakage.
common failure.

[heavymachines]

Re: Mangavox 50ME314V/F7 "Funai junk"

just decided to replace both boards since this tv has multiple things going on. there was an attempt to repair this tv by another shop and far as i can tell its a butchered mess with multi symptoms. The mains cpu is cooked and sloppy solder jobs on bottom and power supply not having standby etc its getting crazy. after i replace both boards if i find bad leds no biggie easy to handle other than dealing with glass.



Thanks for all your help but no schematics and this can get too hairy for all of us and not economical.


I will update results as i always do.

[zape]

Re: Mangavox 50ME314V/F7 "Funai junk"

No standby is normal for Funai power boards
I fixed one of the boards recently and it works without standby voltage.

[budm]

Re: Mangavox 50ME314V/F7 "Funai junk"

No standby is normal for Funai power boards
I fixed one of the boards recently and it works without standby voltage.

Are you saying that if AL+3.3V standby Voltage is not present and that is OK?
So the TV works without standby Voltage, hmmm.

[zape]

Re: Mangavox 50ME314V/F7 "Funai junk"

Are you saying that if AL+3.3V standby Voltage is not present and that is OK?

In my case the AL+3.3V rail on the PSU side was not populated with any components at all. No voltage when PSU is disconnected from Main.
I did not check if there is a voltage present when the main board is connected though.

[zape]

Re: Mangavox 50ME314V/F7 "Funai junk"

So the TV works without standby Voltage, hmmm.

Yes I think they use +13 or +21 rail to produce the "3.3v standby voltage for the mainboard"
They skimp on components to reduce BOM cost wherever possible

[budm]

Re: Mangavox 50ME314V/F7 "Funai junk"

The power supply board itself is made to have the 3.3V regulator installed but for this TV model the Regulator for 3.3V is on the main board so the IC is not installed on the power supply board. That 3.3V is fed back to the power supply board to run the backlights error detection circuit.
The blank PCB is used in many version and model TV so it is cheaper for them to make one blank board that can serve many TV model, but the bottom line is that the TV always need standby Voltage, the AMP+13 and PON+21V are an always on power supply just not at full Voltage when TV is in standby mode.

[heavymachines]

Re: Mangavox 50ME314V/F7 "Funai junk"

In my case the AL+3.3V rail on the PSU side was not populated with any components at all. No voltage when PSU is disconnected from Main.
I did not check if there is a voltage present when the main board is connected though.

That is what page one of schematic was saying budm provided,,,, saying the source of al=3.3v is on main.

[heavymachines]

Re: Mangavox 50ME314V/F7 "Funai junk"

so with all this being said the power supply is probably ok. didn't order anything just yet btw.

[freakaftr8]

Re: Mangavox 50ME314V/F7 "Funai junk"

Look on bottom of mainboard. Under and around the amp IC. This is the IC that's underneath the heat sync. There are four MLCC capacitors around one pico farad I believe they're in a square pattern. You will probably find one of them shorted normal ohm rating should be around 500 ohm.

Just dealt with this the other day and finally found the problem. Remove that cap and either replace it or run it open and see if your 3.3 V comes back. 1st measure all 4 caps And see if one is reading 0 Ω or close to.

Yes the main board generates the 3.3 v back to the power supply on this model. With mainboard shorted all 21 vault and 12 V and free points revolt will be run down on the power supply causing the transformer to chirp as it tries to run up the voltages

[freakaftr8]

Re: Mangavox 50ME314V/F7 "Funai junk"

And yes... Funai junk indeed!!

[budm]

Re: Mangavox 50ME314V/F7 "Funai junk"

C3637?
https://www.badcaps.net/forum/showth...637#post783060

But OP has AL+3.3V when all the boards are connected.

[heavymachines]

Re: Mangavox 50ME314V/F7 "Funai junk"

C3637?
https://www.badcaps.net/forum/showth...637#post783060

But OP has AL+3.3V when all the boards are connected.

had until it started to chrip. had a bunch of shorted smd caps right under cpu removed and still shorted so cpu is toast now and gets really hot.. Another main on its way. it had AL+3.3V until we did that trace cut and forced on backlights which it worked for about 5 seconds then shut down and started chirping and cpu gets really hot. will report back when it comes in.

[heavymachines]

Re: Mangavox 50ME314V/F7 "Funai junk"

Okay replaced main and all is well now and working as it should. stby is provided on main...