TCL 65S517 No Backlight, Picture and Sound OK

[R_J]

Re: TCL 65S517 No Backlight, Picture and Sound OK

I think I spotted your problem... R649 (22Ω?) is blown/missing, it should be the same as R652. I suspect QW4 could be damaged as well

So you have good vcc and the enable is also ok, Check the VBUS voltage, careful this is the hot side of the power supply.

[rebelkustoms]

Re: TCL 65S517 No Backlight, Picture and Sound OK

If you follow the trace from pin 15, it connects to J5 & J43, that is ground. I would check pin3 for VCC and pin4 for enable (BL_on)

So if I read that right I get P3-12v and P4-3.2V. The pins I tested are noted on the pic.

[R_J]

Re: TCL 65S517 No Backlight, Picture and Sound OK

If you follow the trace from pin 15, it connects to J5 & J43, that is ground. I would check pin3 for VCC and pin4 for enable (BL_on)
Check the voltage between hot ground (L602) and VBUS+ (L601)

[rebelkustoms]

Re: TCL 65S517 No Backlight, Picture and Sound OK

So what is the P/N of the IC?
Vin = vcc

So if I am testing this right as per the picture i drew on, neither of those pin have voltage. I was guessing that 1 on the board denotes 1st pin on that IC.

[rebelkustoms]

Re: TCL 65S517 No Backlight, Picture and Sound OK

OZ9976AGN
Intelligent Lighting
Offline LCD Controller

[budm]

Re: TCL 65S517 No Backlight, Picture and Sound OK

So what is the P/N of the IC?
Vin = vcc

[rebelkustoms]

Re: TCL 65S517 No Backlight, Picture and Sound OK

TS3 is the Gate drive transformer for driving the MOSFET's QW3, 4.
The primary side of TS3 is driven by that LED driver IC U601. I would not remove TS3 at this point.

Need to look up the specsheet of U601 to locate the VCC pin and ENA pins to find out what Voltage it has on those pins.

I pulled the spec sheet. I see the ENA pin, but which would be considered the VCC pins? Would it be one or both of those top driver pins? Sorry I dont read a ton of schematics. Mostly only on Pinball Machines.

[nomoresonys]

Re: TCL 65S517 No Backlight, Picture and Sound OK

It's going well, looks like you have isolated the issue to the powerboard.

[rebelkustoms]

Re: TCL 65S517 No Backlight, Picture and Sound OK

TS3 is the Gate drive transformer for driving the MOSFET's QW3, 4.
The primary side of TS3 is driven by that LED driver IC U601. I would not remove TS3 at this point.

Need to look up the specsheet of U601 to locate the VCC pin and ENA pins to find out what Voltage it has on those pins.

OK will do, I checked the pins LED driver pins at the plug and with the set on and showing picture but no backlight I am getting no voltage on any of those pins. I am going to look up the sheet on U601 and check those pins

[budm]

Re: TCL 65S517 No Backlight, Picture and Sound OK

TS3 is the Gate drive transformer for driving the MOSFET's QW3, 4.
The primary side of TS3 is driven by that LED driver IC U601. I would not remove TS3 at this point.

Need to look up the specsheet of U601 to locate the VCC pin and ENA pins to find out what Voltage it has on those pins.

[Diah]

Re: TCL 65S517 No Backlight, Picture and Sound OK

you can do measure on QW3 /4 if there voltage.. be sure only to use HOT area GND probe

[rebelkustoms]

Re: TCL 65S517 No Backlight, Picture and Sound OK

yes you are correct R680/R681..
Ov reading at BL socket are 100% open circuit / crack at power boards connection or at printing lines so start with re solder TS3, and also the driver circuit of it at Hot area.
just be sure if you working on Hot area the GND should be taken from same area not from GOLD Area or TV chassis.

I am about to resolder TS3, I included a pic there is a resistor on the hot side R649 that has some weird coloring around it. Not sure if it is flux or a light corrosion but it looks odd. Thoughts?
Also when you say resolder the driver circuit what are are we talking about on the hot side?

[rebelkustoms]

Re: TCL 65S517 No Backlight, Picture and Sound OK

What is the P/N of the LED driver IC U601?
Also check that rectangular grey cap C620, it looks like one of the leg did not poke through to the bottoms side of the board.

Here is what is on the IC from what I can read

OZ9976AGN
CK765K. 1N
1839 A1

Also that was just a bad picture angle on the Capacitor 620, Both legs are through the board and the joints look good.

[Diah]

Re: TCL 65S517 No Backlight, Picture and Sound OK

So I am thinking you mean R681 and R680 (the ones right next to the LED Pinouts) they are both reading 0.1 ohm or 0.2 ohm.

yes you are correct R680/R681..
Ov reading at BL socket are 100% open circuit / crack at power boards connection or at printing lines so start with re solder TS3, and also the driver circuit of it at Hot area.
just be sure if you working on Hot area the GND should be taken from same area not from GOLD Area or TV chassis.

[Dido210]

Re: TCL 65S517 No Backlight, Picture and Sound OK

I would first test voltage on the power supply board LED connector pins. disconnect the connection I circled, if you are getting voltage while they are not connected to the board then its going to be bad LED's and would require that you open the display assembly to test. if you don't get any voltage when powering on then the fault is in the Power Supply board.

My Company works repairing TCL tv's under warranty so i have gotten lots of experience with these type of issues. my best guess would be that your LED strips are the problem.

Best of luck and be careful if you end up opening the screen assembly. the screen is very thin and fragile. especially near the bottom flex cables.

[budm]

Re: TCL 65S517 No Backlight, Picture and Sound OK

What is the P/N of the LED driver IC U601?
Also check that rectangular grey cap C620, it looks like one of the leg did not poke through to the bottoms side of the board.

[rebelkustoms]

Re: TCL 65S517 No Backlight, Picture and Sound OK

you might want to try trace back the one pin that is not showing 12v as that seems rather strange.

Here are corrected voltages, I checked again twice, i must have gotten a pin off towards the bottom. That pin did have 12v, also all those 12v are on the same trace.

P-Dim=3.26v BL_ON=3.26v
GND= 0v P_ON = 2.34v
NC=0 A_DIM=0v
GND= -35mv GND= -35mv
12V = 12v 12V = 12v
12V= 12v 12V= 12v
12V= 12v 3D_En= 0v

[budwich]

Re: TCL 65S517 No Backlight, Picture and Sound OK

Sorry, I flipped the Main Board when I was first testing to look for pin outs, I hadn't noticed this cord had a double pin set. my mistake. here are voltages and a picture of the bottom of the PS for reference.

P-Dim=3.26v BL_ON=3.26v
GND= -34mv P_ON = 2.34v
NC=0 A_DIM=12mv
GND=-35mv GND= -35mv
12V = 12v 12V = 12v
12V= 12v 12V= 0v
12V= 12v 3D_En= 0v

you might want to try trace back the one pin that is not showing 12v as that seems rather strange.

[rebelkustoms]

Re: TCL 65S517 No Backlight, Picture and Sound OK

Are you getting about 380 ~ 400 VDC measured between the two legs of the main filter caps CE1, CE2?

HI Budm, I am getting 396 VDC on both of those caps.

[rebelkustoms]

Re: TCL 65S517 No Backlight, Picture and Sound OK

while the set OFF remove the LED socket from PSU. and measure with Ohm the 2 SMT resistors R581 R580

So I am thinking you mean R681 and R680 (the ones right next to the LED Pinouts) they are both reading 0.1 ohm or 0.2 ohm.