SMPS schematic for Samsung UN46EH5000?

[nomoresonys]

Re: SMPS schematic for Samsung UN46EH5000?

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[nomoresonys]

Re: SMPS schematic for Samsung UN46EH5000?

Might be easier to just replace the leds with the same type that are already in there, they're pretty cheap, 100 for a few bux right?

[arizanotlari]

Re: SMPS schematic for Samsung UN46EH5000?

Might be easier to just replace the leds with the same type that are already in there, they're pretty cheap, 100 for a few bux right?

This explanation is about znl193:

Backlights is ok but leds flashing: replace fan7340. If still flashing check resistor of pin 13. If all resistors ok add a 100k resistor to pin 13.

I write this topics because this psu also using fan7340. This modification working znl193. I dont try different psus.

[Unspun01]

Re: SMPS schematic for Samsung UN46EH5000?

Good evening all!


Right now, the backlight momentarily blinks on (all of them), then the supply shuts off. The backlight controller is a "SLC1012C" -- looks like this is equivalent to a Fairchild FAN7340.

I tried this one time.

I had many LEDs burned. Probably almost 30 out of 44. Horrible TV.

SLC1012C IC on my power supply had a burnt spot.

I could not locate a replacement IC to buy it. I assumed FAN7340 was equal but upon installation it caused backlight strobing/flicker.

I don't think the FAN7340 is a direct replacement for SLC1012C.

My final repair consisted of swapping the good LCD panel to another cracked screen TV chassis with good backlights and power supply.

[ngth82]

Re: SMPS schematic for Samsung UN46EH5000?

I had a few minutes to take a look at the unit before heading out again...

Panel model number is a Samsung CY-DF460BGLV1H.
The SMPS board is #BN44-00667A / L46GF_DDY

I found a replacement LED strip set on eBay for $25 looking at the panel number only.
These are also available for $49 on shop jimmy: https://www.shopjimmy.com/samsung-bn...s-8-strips.htm

I currently don't have the TV disassembled. Looks like CY-DF460BGLV1H uses the BN96-28768A and BN96-28769A strips. I couldn't find a lead on the strip LED specs. Maybe someone here has that information?

Looking the SMPS board, pin 13 is OVP, the resistor divider is 6000 kOhm to VLED (VOUT) with a 82kOhm to ground. This sets the OVP at 220V.

If you add a 100kOhm pull down to pin 13 (i'm assuming Arizanotlari means in parallel with the existing pull down), that sets the effective pull down value to 45kOhm and OVP is effectively 400V in this case.


I'll set it to 300V and see what happens. I've already replaced the LEDs in the strip with ones that i have laying around instead of using the exact replacement which is why i'm in this mess in the first place.

Lets give it a go.

Thanks!

[ngth82]

Re: SMPS schematic for Samsung UN46EH5000?

Success! I modified the OVP circuit for testing.

The FAN7340 datasheet shows the typical application circuit for pin 13 (OVP) as a resistive divider for VLED.

• ROVP1 = top side resistive divider to VLED.
• ROVP2 = bottom side resistive divider to GND.

The BN44-00667A power board that i have uses:

• ROVP1=6000 kOhm
• ROVP2=82kOhm
• VOVP = VLED * ROVP2 / (ROVP1 + ROVP2)
• 3V = VLED * 82K / (6000K + 82K)
• 3V = VLED * 0.0135
• VLED = ~220V

As mentioned in post #25, this sets the OVP to 220V by default. The OVP pin trips when it goes above 3V.

I changed ROVP2 to 50kOhm for testing. This gives an effective VLED of 360V before OVP trips.

• ROVP1=6000 kOhm
• ROVP2=50kOhm
• VOVP = VLED * ROVP2 / (ROVP1 + ROVP2)
• 3V = VLED * 50K / (6000K + 50K)
• 3V = VLED * 0.00826
• VLED = 3V / 0.00826
• VLED = ~360V

The backlights turn on. The VLED voltage is sitting at 234V relative to chassis ground.

Looks like I can adjust the value somewhere around ~70 kOhm for an OVP value around ~260V and should be okay.

This should work out since I replaced all 44 LEDs with higher Vf LEDs that i have laying around. My LED tester showed the ORIGINAL LEDs with a Vf of 2.6-2.7V. The new LEDs have a Vf of 2.9V. The modified strips require an additional ~13V output from the supply to operate.

Going to mod the board again. I'll provide an update shortly.

[ngth82]

Re: SMPS schematic for Samsung UN46EH5000?

Looking at the oscilloscope, the VLED node doesn't go above 235V

I modded the OVP circuit to 300V. Seems to work. I'm just going to leave it alone.

Issue closed.

[budm]

Re: SMPS schematic for Samsung UN46EH5000?

https://assets.shopjimmy.com/media/c...00667a-top.jpg
Something does not add up, the LED Voltage chart for the BN44-00667a is rated at 168V @470mA and your result is 234V: "The backlights turn on. The VLED voltage is sitting at 234V relative to chassis ground."

[ngth82]

Re: SMPS schematic for Samsung UN46EH5000?

Budm -

Agreed. I was testing the HDMI inputs on the unit and the backlights failed. Looks like one of them are now open in the string. The output rating is indeed 168V @ 470mA. With 44 LEDs, that is a max voltage of 3.8V each @ 10.6mA.

The reading i see is 234V relative to chassis ground or 5.3V per LED. That's not right.

The TV has four LED strings - all in series. The connector is 9 pins. There are three pairs of wires in the wiring harness. The first two strings are connected in series together for pins 2-3, followed by the second string on pins 4-6, and the third string on 7-8.

Perhaps I have a couple of bad replacement LEDs to begin with?

I'll disassemble this set when i have some additional time to do so. Until then, i can look for better LEDs instead of ones from eBay (or just purchase a replacement LED strip set).

Do you have a source for tracking down LED strip specs? The panel and strips are as follows:

CY-DF460BGLV1H
BN96-28768A
BN96-28769A

Thank you,
Thomas

[budm]

Re: SMPS schematic for Samsung UN46EH5000?

" The output rating is indeed 168V @ 470mA. With 44 LEDs, that is a max voltage of 3.8V each @ 10.6mA.
That is not how it works, LED are connected in series so the current will be the same on all LED's. The VF of the LED will vary with the forward current, so if test the LED ai only 30mA, the Vf will show <3V.
The total VLED is the VF of the LED string + the Vdrops (20V is TYP.) of the PWM Controlled MOSFET on the low side for maintaining the constant current through the LED string.
At 234V reading, that is way off chart.

[budm]

Re: SMPS schematic for Samsung UN46EH5000?

What is the Vf of each LED string when you use your LED tester?

[ngth82]

Re: SMPS schematic for Samsung UN46EH5000?

What is the Vf of each LED string when you use your LED tester?

Ah brain fart. Thanks for the correction on post 30.

Using the LED tester on the remaining two strings, each string has a Vf=31.3V. For curiosity, i put my multimeter in series with it and measured 33mA through the string.

[budm]

Re: SMPS schematic for Samsung UN46EH5000?

Your tester has constant current source of around 30mA (My tester also has about 30mA of testing current), so the Vf will shows lower Vf, about 2.7V or so for each LED, but when driven at much higher current, the VF will be around 3V or so, that is why I put up the spec sheet of the LED in post #6 to shows the Vf VS If graph to show how Vf is affected by the If.

[ngth82]

Re: SMPS schematic for Samsung UN46EH5000?

Thanks. Yes, this tester is around 30mA - it's the GJ2C model that is sold on shopjimmy and elsewhere.

I must have missed your post #6. I was out on business travel. I see what you are stating. The forward current increases with the forward voltage.

I still have all of the original LEDs that i pulled off from the strings. I'll see about finding the handful that are still good and apply varying Vf and plot the corresponding If.

The seller that i bought the LEDs from doesn't have that information posted. I'll ping them to see if there is a graph available.I will do the same with the replacement LEDs and see what i get in lieu of having that information from the vendor.

Thank you.

[ngth82]

Re: SMPS schematic for Samsung UN46EH5000?

I was able to find a working LED from the original panel strip. I measured the voltage vs current and plotted the data. The original LED starting flashing above 3.4V. I wouldn't place too much emphasis above that voltage.

I heard back from the seller too - all they are just claiming is "Vf=3.0-3.2V, If=20mA"

[budm]

Re: SMPS schematic for Samsung UN46EH5000?

It looks like your old LED is rated at about 350mA at most, so when you push higher current it starts breaking down, it is a 1 Watt LED.
The power supply is capable of delivering 470 mA but it is not being used at max rating in your TV, more likely at 300mA or so.
"all they are just claiming is "Vf=3.0-3.2V, If=20mA"
Your replacement LED is not rated at 1W for sure, that is why it starts cutting out when forcing high current through it. So your replacement is no good as I suspect from the beginning, seller should be able to tell you the max current rating spec, I would not buy from seller like that. It is good that you learn to plot the LED graph.

[budm]

Re: SMPS schematic for Samsung UN46EH5000?

https://www.ebay.com/itm/50-Pieces-l.../201821440464?

https://www.aliexpress.com/item/32788776719.html

This is what I use for some of the Samsung backlights with big pad as negative, but these day I replace the whole set of strips instead of replacing a bunch of bad LED's and gluing back the LENS, not worth the time any more for me.

[ngth82]

Re: SMPS schematic for Samsung UN46EH5000?

Hey Budm - as always thanks for the feedback and constructive criticism. I’ll look at the LED suggestions from your sources

I’ll also weigh the time/effort in replacing all 44 again vs buying replacement strips. That took about 2 hours the first go. I agree that the lens replacement was a PITA - E6000 glue worked well though. I’ll likely have time to take apart the set in 2-3 weeks since the Christmas tree is now taking up the front room work space.

Regards and have a great evening!

[budm]

Re: SMPS schematic for Samsung UN46EH5000?

Thanks, this is a great place to learn, and thanks for the graph, now I can tell people how to see the effect of LED current and the Vf using your graph.
And if the Vf rating at 3V (3.2V typical for high end), you can see that the replacement LED is rated at about 20mA.

[ngth82]

Re: SMPS schematic for Samsung UN46EH5000?

Fantastic! Yeah, feel free to use it