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Electronics => Repair => Topic started by: Shirakaba on August 01, 2015, 02:42:44 pm

Title: [SOLVED] Samsung TV LE46C535F1W (main board BN94-02616Z)
Post by: Shirakaba on August 01, 2015, 02:42:44 pm
I have been trying to repair a Samsung TV model LE46C535F1W with a BN94-02616Z main board. When trying to wake it up from suspend, the power led blinks five times and then everything remains off.

Hoping that it would be a power supply issue, I have replaced some of the capacitors on the power supply board. Since that didn't improve things, and after reading that it could be a main board issue, I did some troubleshooting there as well. After spraying the upper right corner (the "power corner") with some freeze spray, it actually turned on! After having narrowed it down quite a bit, it seems to be related to the flash memory (located right above the top-right corner of the heat sink). It does not seem to be related to any passives around the flash memory, but I am not quite sure.

I am curious to hear if anyone has a theory of why it starts working when the flash memory has been cooled down.

Could this be a symptom of something else being defective, which propagates to the flash memory?

Can this be repaired in any way, or will I need to replace the whole card?


Regards,
Shirakaba
Title: Re: Samsung TV LE46C535F1W (main board BN94-02616Z)
Post by: mij59 on August 01, 2015, 03:13:25 pm
Found this http://www.badcaps.net/forum/showthread.php?t=26166  (http://www.badcaps.net/forum/showthread.php?t=26166), one of the suggestions is data corruption in the memory on power down caused by a faulty main power supply board. Maybe one of the capacitors has lost too much capacity causing a supply voltage to drop out before the data has been written to the memory.

Did you check voltage regulators in the top right corner of the main board ?
 
 
Title: Re: Samsung TV LE46C535F1W (main board BN94-02616Z)
Post by: Shirakaba on August 01, 2015, 04:39:26 pm
I have been poking around with the multimeter as well as the oscilloscope and found a few things that may be of interest:

Title: Re: Samsung TV LE46C535F1W (main board BN94-02616Z)
Post by: Shirakaba on August 01, 2015, 04:41:41 pm
Another suggestion is that it may be either an ESD issue or a cold solder joint, which is temporarily fixed by freezing the flash IC.
Title: Re: Samsung TV LE46C535F1W (main board BN94-02616Z)
Post by: mij59 on August 01, 2015, 05:03:14 pm
Quote from: Shirakaba on August 01, 2015, 04:39:26 pm
I have been poking around with the multimeter as well as the oscilloscope and found a few things that may be of interest:

  • The regulator next to the PCMCIA socket is converting 5.16V to 3.32V and is the only one that is running when the TV is in standby. Power supply for the nearby TQFP, which appears to be a WT61P802 - Flat Panel Display Control Sub-MCU.
  • The buck regulator next to the upper right connector is converting incoming 12.5V to 3.3V when the TV is turned on (even if it fails). Same goes for the 2.5V-regulator on the middle right edge of the board.
  • The rail which measures 12.5V is supposed to be 13V according to the silk screen on both the PSU-board and main board. Could this be a power supply issue after all?

I don't think the  12.5 V is a problem, if there's no excessive ripple its OK, you could check the power supply board how the 12.5 V is generated.
Title: Re: Samsung TV LE46C535F1W (main board BN94-02616Z)
Post by: mij59 on August 01, 2015, 05:05:53 pm
Quote from: Shirakaba on August 01, 2015, 04:41:41 pm
Another suggestion is that it may be either an ESD issue or a cold solder joint, which is temporarily fixed by freezing the flash IC.

ESD is unlikely, cold solder joint or broken copper trace maybe hard to find and fix.
Title: Re: Samsung TV LE46C535F1W (main board BN94-02616Z)
Post by: Rasz on August 02, 2015, 01:01:01 am
solder joint can be diagnosed witha  finger
turn off tv, discharge yourself (metal frame of tv?), push flash chip with your finger into the pcb, turn on
reflow if it powers up
Title: Re: Samsung TV LE46C535F1W (main board BN94-02616Z)
Post by: fluxcapacitor on August 02, 2015, 01:02:30 pm
Another suggestion from badcaps, try a eeprom reset .

http://www.badcaps.net/forum/showthread.php?t=26166 (http://www.badcaps.net/forum/showthread.php?t=26166)

http://wiki.samygo.tv/index.php5/UnBricking_TV_by_EEPROM_Reset#LExxC550.2F530 (http://wiki.samygo.tv/index.php5/UnBricking_TV_by_EEPROM_Reset#LExxC550.2F530)
Title: Re: [SOLVED] Samsung TV LE46C535F1W (main board BN94-02616Z)
Post by: Shirakaba on October 24, 2015, 06:29:25 pm
Since various attempts on reflowing the flash memory took me out of the frying pan, into the fire, I solved it by simply replacing the main board with a BN94-03985H.

Thanks for all your input!