Hi!
I have a Samsung UE40F7000 TV that won't turn on fully. From standby the relay clicks and attempts to start, then turns off again. Ive managed to find the diagrams here BN44-00632 (A plus the B modification).
I do have experience of electronics repair and basic test equipment so Im looking for some help to get this diagnosed.
So far I can see a nice health 390v across the 2 large electrolytics and the A5V rail is steady at 5.3vdc whereas the B5V along with the 13v is pulsing in time with the relay clicking on/off every second.
Ive had a look around for dry joints and any damaged components, swollen caps etc but nothing obvious.
Would love some assistance to save my perfectly good tv from the recycling!
Thank you!
p.s. How do I register for the forum?
Hello
Disconect power board from main board, if power board is OK you must see backlight is illuminated.
If power board OK, then maybe boot software problem in main board's chip WT61P807
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Thank you - when I disconnect the main board the rate of the relay clicking increases and the backlight briefly flashes on, then clicks and repeats. Will these PSU boards run without the 13v and B5V loaded?
I’m tracing the feed to the relay coil and get a steady 5v to one side from the standby supply. I see from the ‘A’ version of the PSU diagram there looks to be a FAIL_OUT which connects to the small MOSFET to pull the coils to 0v. I perhaps need to look more closely at.
FYI when I measure the PSU_ON line it’s sat at 3.3vdc and drops to 0 on the click. Should it be higher?
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If clicking and repaats without main board then PSU is bad. These PSU work without main board.
PSU_ON is 3.3V, it is good.
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So it seems the FLT leg on the 3321 backlight controller chip is pulsing which looks to be triggering the shutdown.
The Current Sense inputs from across the 0.1R resistors generates no voltage, plus the Over Voltage Protection inputs are around 3v. Supply voltages to the Driver Power 1A and 1B are pulsing to 35v and 1C, 1D, 1E are hitting 70v - seems OK (based on cap ratings and transformer windings) but confirmation would be good if anyone knows?
What other conditions cause the FLT to be raised?
See Magnachip document US 20140159217A1
Thank you
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Üdv
I suspect you have a backlight problem. FLT is LED failure protection, which shuts down the power supply.
It is possible that one of the LEDs is shorted, causing a large current to flow, which is why the protection intervenes.
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Thanks - the problem exists with the backlights disconnected.
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Further investigation shows that both of the backlight controller ICs are pulsing their FLT pin (checked from behind the diode, IC side).
Looks more likely a common issue perhaps under or over voltage from the supply.
Just going to have to find a point when it’s working and take lots of measurements to compare.
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I assumed you already checked the power supply voltages.
PFC is working, 400Volts ok?
But a software error cannot be ruled out either.
You have the TV,
you know more because I'm just assuming.,if there is no accurate diagnosis
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Hi, yes Im getting 390v peaking across the main power supply, though it pulses due to the relay.
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Then.......?
Ther is the error,,,the pfc power supply voltage must be stable
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VCC to the SPC7011F is pulsing, though that's expected because the VCC is controlled by the opto isolator (in parallel with the relay coil), triggered by the FAIL circuit from the FLT pin.
This is the closest diagram I can find. Mostly the same except some IC's are slightly different https://elektrotanya.com/showresult?what=bn44-00632&kategoria=&kat2=all
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Üdv
Yes, yours is an interesting version, with a control IC that has no datasheet anywhere,,,,,
Where do you live? Where did you buy the TV?
Write down all the ICs that are on your power supply panel,
for example: Power,PFC.LED driver,,,
The PFC power supply has a 47ua capacitor, is that good?
You write "VCC to the SPC7011F is pulsing, though that's expected because the VCC is controlled by the opto isolator (in parallel with the relay coil), triggered by the FAIL circuit from the FLT pin." NO
The pfc and opto get power from T801 + C805 filter
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Thanks - yes CS805 is good as it's been replaced, along with all other electrolytics! Voltage measured good across that, 20v or so if I recall.
The board is from UK sourced, UE40F7000
PSU board:
L46F2P_DDY / BN44-00632B
PCB rev 1.1
Date 13.01.25
IC's:
2A1530 (standby power driver)
C25600 (LLC Controller)
SPC7011F (PFC controller)
SLC2013M (backlight driver channels 1&5)
SLC1013M (backlight driver channels 2&3&4)
I managed to take some measurements across the SLC2013M when it was working, and when at fault. As follows;
Really appreciate your help.
Update! - I disconnected both of the diode-OR'd FLT signals from each of the SLC IC's (there are some PCB jumpers which can be easily lifted). The PSU remained stable and produced a steady output and no relay clicking. I did it briefly incase anything is under stress. At the same time I measured the IC side of the disconnected lines and they both measured a steady 5v. So it seems conclusive it's those which are causing the shutdown.... now why!?
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HI
Based on your information, I first suspected that you had an LED backlight problem..,,,,,it still exists.
To rule this out, you should try the LED backlight from a separate power supply..,,,
of course, a power supply with which you can set a current limit.
Or,, you can apply 3-Volt to the LED diodes one by one with a pin contact and the LEDs should glow dimly....
they should light up evenly........I've already tried this, it works.
But for this you have to disassemble the display,,,
very carefully,,when you lift the LCD, don't strain the cable because it can break easily.
Sometimes the LED breaks, but sometimes it gets shorted.
What confuses the led driver controller
One more
This model is UE40F7000,,,this is not enough,,,,for example,,,,,,,,,,,UE40F7000xxec
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UE40F7000STXXU
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hello.
https://elektrotanya.com/dotest
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