backlight issue Samsung UE32EH5000

[Mikeyboy2007]

Hi Guys i have the Samsung LED model UE32EH5000 when it is switched on i get no backlight. i have tested the LED strips and all check out. the voltages i get from the power supply to backlights is.

182v
182v
0v
278v
278v

and the voltages i get from PSU to AV board is.

13.10v
13.10v
13.10v
13.10v
0v
5.27v
5.27v
0.90v
13.10v
4.88v
0v
0v
5.29v
3.54v

does anyone know what the issue is or what i can do to further troubleshoot. thanks.

[Doc38343]

Re: backlight issue Samsung UE32EH5000

Do the backlights do anything when you turn it on like blink?
Have you tried it with the power jack going to the main board disconnected?
How did you test the LED strips?

Had a similar issue recently but not exactly the same. Mine had one LED working intermittently and I found it had a bad solder joint on the led. I killed it trying to fix.. but put a new bulb on later.

[Mikeyboy2007]

Re: backlight issue Samsung UE32EH5000

hi there thanks for quick reply. backlights do nothing at all when tv turns on. tried it with cable to main disconnected and got no blinks from backlights at all. i tested the led strips using a LED tv backlight tester and all when on no proeblem as i stripped screen out to check.

[dick_barton]

Re: backlight issue Samsung UE32EH5000

Do you have a single led string. If so I would check the mosfet on the return side of the led string.

[Mikeyboy2007]

Re: backlight issue Samsung UE32EH5000

there is 4 or 5 led strips inside tv.

[dick_barton]

Re: backlight issue Samsung UE32EH5000

I believe they are all connected in series since Pin1 & 2 are TOP1+, Pin 3 no connection Pin 4 & 5 TOP1-
Also 140V for 3V leds would be approx 47 leds in series.

[Mikeyboy2007]

Re: backlight issue Samsung UE32EH5000

what can i do to further test ? could the PSU be at fault if all LEDs seem to be ok ?

[budm]

Re: backlight issue Samsung UE32EH5000

The LED power supply Voltage chart shows 140V as printed on that power supply board.
What Voltage does it show on your LED tester?
Since you are getting 278V then it has open circuit some where.

[Mikeyboy2007]

Re: backlight issue Samsung UE32EH5000

im guessing that would be fault with the power supply ? and will test with LeD tester just now and report back.

[dick_barton]

Re: backlight issue Samsung UE32EH5000

No, its indicating a possible led problem (shorted led(s)) or an interconnection problem between the led strips.

Edit
Shorted leds would not stop the led tester working but a shorted led would trigger the protection shutdown of the led controller IC.

[budm]

Re: backlight issue Samsung UE32EH5000

im guessing that would be fault with the power supply ? and will test with LeD tester just now and report back.

As dick_barton has indicated, it can also be that the MOSFET on the return side may be bad on not being turned on.
Right now the power supply is not seeing the load so its output went up high.

[budm]

Re: backlight issue Samsung UE32EH5000

OK, I just look at the bottom side of the board at shopjimmy, the LED return is done through the MOSFET inside the LED driver controller IC 9101S.
Get the P/N of that IC so we can look up the spec. sheet.
Pictures provided by shopjimmy.
BTW, no one work on this TV before, right?
Shop jimmy only shows 2 LED strips.
http://www.shopjimmy.com/samsung-cy-...s-2-strips.htm

[Mikeyboy2007]

Re: backlight issue Samsung UE32EH5000

tested led strip with tester as a whole and per strip. i am getting 113v for whole string and 28.1v per strip. @Budm the IC P/N is PC1AC SLC101 0

as far as im aware tv has never been opened or tampered with.

[R_J]

Re: backlight issue Samsung UE32EH5000

It looks like in post #1 you measured the led voltage with reference to chassis, You should measure across cn802, positive probe to pin 1 and negative to pin 5

[Mikeyboy2007]

Re: backlight issue Samsung UE32EH5000

@R_J yes i measured with MM from ground on chassis and red probe on pins. will do that just now and reply.

[Mikeyboy2007]

Re: backlight issue Samsung UE32EH5000

It looks like in post #1 you measured the led voltage with reference to chassis, You should measure across cn802, positive probe to pin 1 and negative to pin 5

with probes on 1 and 5 i get 0v with multi meter set to 200 and 250

[R_J]

Re: backlight issue Samsung UE32EH5000

What voltage do you get across C9111, you may need to check that when you first turn the tv on.

[Mikeyboy2007]

Re: backlight issue Samsung UE32EH5000

ok i flipped up PSU to read voltages on C9111. when i plugged in it went to 14, 17 then 19 then 1 displayed. i unplugged tv and voltage appeared 180 or so tjen gradually dropped. took 2 minutes for it to go back to 0v after switching off from plug.

[budm]

Re: backlight issue Samsung UE32EH5000

with probes on 1 and 5 i get 0v with multi meter set to 200 and 250

That means the GND return for the LED is open which will be the internal MOSFET inside the LED controller IC. I did not look up the spec sheet for that IC yet.

[dick_barton]

Re: backlight issue Samsung UE32EH5000

The voltage listing for CNM803 (post #1) does not look correct. Could you list the Pin number, legend, voltage read
Pin1, B13V , 12,8V
Pin2
Pin3
Etc