Samsung UE48JU6400W - back light on, sound on, sometimes picture.

[dronerat]

Re: Samsung UE48JU6400W - back light on, sound on, sometimes picture.

Maybe do a factory reset while you have it working.

From the TV menu or from the Service menu?

[nomoresonys]

Re: Samsung UE48JU6400W - back light on, sound on, sometimes picture.

I'd go with tv menu, maybe the new thermal paste is what it needed to keep it from getting a little too hot and acting up, looks like it's doing a lot better.

[dronerat]

Re: Samsung UE48JU6400W - back light on, sound on, sometimes picture.

I'd go with tv menu, maybe the new thermal paste is what it needed to keep it from getting a little too hot and acting up, looks like it's doing a lot better.

Did the factory reset. After the TV restarted the panel stopped working again

[nomoresonys]

Re: Samsung UE48JU6400W - back light on, sound on, sometimes picture.

That should not happen, starting to think the eeprom is messed up.

[nomoresonys]

Re: Samsung UE48JU6400W - back light on, sound on, sometimes picture.

Maybe try the reset from service menu if you can get it to start again, should start the same way you did it before: https://www.youtube.com/watch?v=wyKEJOy8tqo

[nomoresonys]

Re: Samsung UE48JU6400W - back light on, sound on, sometimes picture.

Check and see if you have IC7301 on that mainboard, would be an 8 pin eeprom.

[dronerat]

Re: Samsung UE48JU6400W - back light on, sound on, sometimes picture.

Check and see if you have IC7301 on that mainboard, would be an 8 pin eeprom.

I have looked through all the components on the board, but did not find IC7301. If you are referring to the main eeprom I think it is IC1101. It also has eeprom test points.

Im thinking of trying to connect EEPROM_SDA and EEPROM_GND or EEPROM_SDA and EEPROM_VCC and turn on the TV to see if it turns on. I will not disconnect the EEPROM_SDA and GND/VCC signals while the TV is so that I will not erase the eeprom.

As far as I read it should force the TV to turn on with default settings after 20 seconds. If it turns on repeatedly i hope that after that I will be able to fire it up with the current settings, take pictures of the panel info, tuner settings, etc. and perform an EEPROM reset.

What is your opinion?

[nomoresonys]

Re: Samsung UE48JU6400W - back light on, sound on, sometimes picture.

Yes, was going there, that there IS an eeprom reset: (connecting) GND OR VCC (3.3v) to SDA. BUT DO NOT connect both gnd and vcc to sda that would be BAD.

[dronerat]

Re: Samsung UE48JU6400W - back light on, sound on, sometimes picture.

Yes, was going there, that there IS an eeprom reset: (connecting) GND OR VCC (3.3v) to SDA. BUT DO NOT connect both gnd and vcc to sda that would be BAD.

Ok so I somehow managed to start the TV in service mode with the panel ON. Took a ton of pictures in the different menus just to be sure.

Now the fun thing begins. I connected EEPROM_SDA to EEPROM_GND and have some mixed results.

Now the panel starts 7/10 times, but I still have some of the runs not starting correcly.
I am starting to think that the PSU is acting up on me, because shorting the two signals changed the boot sequence which may have led to the T-Con starting more frequently.
Previously the T-Con was starting just before the backlight, but now the T-Con starts and the backlight starts 20 seconds after that. I am starting to think that the delay in starting the backlight provides just enough stable voltage for the T-Con to start, but not every time (7/10) times.

The crackling noise coming from the PSU in standby which is present in powered on mode (just a lot quieter) is leading me to believe the PSU might be the problem. I am not sure if I will be able to record it and how to upload it here. Sounds like 50hz.

Since the issue is still present with the EEPROM disabled i think that we can rule the EEPROM out of the options causing the problem.

[nomoresonys]

Re: Samsung UE48JU6400W - back light on, sound on, sometimes picture.

I'm not sure what the fail count is suppose to be but other than that your voltages looked pretty good on your testing of powerboard.
, I must defer to the gurus, I bet somebody here knows tho.

[dronerat]

Re: Samsung UE48JU6400W - back light on, sound on, sometimes picture.

I'm not sure what the fail count is suppose to be but other than that your voltages looked pretty good on your testing of powerboard.

I am really out of ideas. The only thing abnormal I see is the sizzling (not really sure how to describe it) coming from the power board. Visually there are no bad components, but I think it is possible to have voltage drops during startup that prevent the T-Con from starting.
I have measured the output voltage and it seems to raise during power on and not go from 9V to 12.8V directly, but this might be due to my crappy $5 multimeter.

I am really considering buying another power board. Will think a bit more and see.

[dronerat]

Re: Samsung UE48JU6400W - back light on, sound on, sometimes picture.

Interesting a similar thread started a few days ago https://www.badcaps.net/forum/showth...ght=fail_count with a similar looking PSU says that Fail Count is 0V.

And the user is having similar but far worse symptoms, but one of them is the TV coming on with backlight but without a picture.

Might give changing the PSU a try.

[nomoresonys]

Re: Samsung UE48JU6400W - back light on, sound on, sometimes picture.

Might have some weak startup electrolytic caps on the powerboard??

[nomoresonys]

Re: Samsung UE48JU6400W - back light on, sound on, sometimes picture.

I've seen an occasional voltage regulating diode read fairly good but still be bad??

[dronerat]

Re: Samsung UE48JU6400W - back light on, sound on, sometimes picture.

Today I ordered a replacement PSU from a TV with a broken screen (at least the seller says that). I should receive it in 1-2 days. Hope it fixes the problem. Will keep you updated.

[dronerat]

Re: Samsung UE48JU6400W - back light on, sound on, sometimes picture.

Ok so changing the power supply gave me hope for just a bit, but it died quickly.

Swapped the PSU boards, and the TV began starting normally more often than before. I said: Well... I'll put it in the bedroom while I get capacitors or something to troubleshoot the board more, but after 2-3 hours of working i powered off the TV and was not able to power it back on since then.

I will get one of these compressed air cans in order to freeze the EEPROM to see if that helps.

The main board and two little PCBs which are after the T-Con are the only things I have not changed on this TV and still cannot get it to work.

Now I Either have to find a suitable replacement for the EEPROM or get a new compatible main board. I am really determined to make this TV work, but I am not sure which will be worth more. EEPROM+shipping+time to change+desoldering/soldering in hopes that it will work, or a replacement board.

I see that Mainboard+Shipping from England to Bulgaria is about 32 GBP The cheapest board I could find here that is a similar model without shipping to my location is about 55 GBP. The EEPROM+Shipping.... etc will be about 15 GBP as I will still need to import it.

[dronerat]

Re: Samsung UE48JU6400W - back light on, sound on, sometimes picture.

Ok now I am really fed up with this TV.

Since my last post I bought a freezing spray and tried to freeze the EEPROM with no success.

Then resorted to buying another mainboard together with the ribbon cable that connects the mainboard with the T-Con.
The TV powered up fine. Managed to set the settings etc.
And left it working for about an hour or two happy that it seemed to resolve the issue.

Turned the TV off and the problem is back again....

I am really out of ideas. I have measured all of the little capacitors on the boards that the ribbon cables to the panel are soldered and none of them is shorted. The only thing I have not changed in this TV are those 2 boards(not really sure that it is possible in a home environment) and the two ribbon cables that are connecting the T-Con with those two boards.

Any opinions will be greatly appreciated.

[nomoresonys]

Re: Samsung UE48JU6400W - back light on, sound on, sometimes picture.

Strange indeed, covered about everything, wonder if the panel is bad, funny that mainboard made it work fine for a minute there, maybe try the "cutoff Tape" method: https://www.youtube.com/watch?v=j7vl7-vZEL8

[dronerat]

Re: Samsung UE48JU6400W - back light on, sound on, sometimes picture.

Strange indeed, covered about everything, wonder if the panel is bad, funny that mainboard made it work fine for a minute there, maybe try the "cutoff Tape" method: https://www.youtube.com/watch?v=j7vl7-vZEL8

That is a thing I will definitely try. This evening I will try to remove the plastic covers from the panel, see if there are more boards there and measure them as well.

I am even thinking of checking the LED strips if I manage to get to them without cracking the screen and also check them. The strange thing is that the panel works perfect until the TV is powered off, so I still have a little bit of doubt that the panel is bad.

Also when either of the ribbon cables going to the buffer boards (those boards after the T-Con) is disconnected the T-Con does not try to start at all.

[budwich]

Re: Samsung UE48JU6400W - back light on, sound on, sometimes picture.

check to see if there is a third led on the tcon. Other threads of samsungs indicate such.
IF so, that is your likely problem.

further, you refer to one of the leds flashing ... which one does this?