LG 55LS4500-UD Shutting down

[brucetv]

This Tv came into our shop today from our local church thrift store so we are going to try to help them out hopefully so they can sell it and help the poor. It has a solid red power light at plug in. When you turn it on the backlights come on for 2 seconds and Tv shuts back off. There is a led on the power supply that blinks 4 times...stops...then 4 blinks ect.
Voltages when plugged in with main connected
P Dim 2 Error 0.11Dc
12v P Dim 12.07
12v NC 12.07
12v Drv On 12.08
GND
GND
3.5 0
3.5 0
GND
GND
24v 24.87
Pwr On 24v 3.406 Thank you for the advice

[Nick's Tvs]

Re: LG 55LS4500-UD Shutting down

Top left of the power supply board you have a transformer. Below you have a blue rectangular capacitor. and then just underneath and to the right you have a diode. That diode is in parallel with the blue capacitor to its right. That capacitor and or diode I have seen short out many times.
Take your multimeter to either or of those 2 components, and check for shorts. Now the picture is to blurry and low quality for me to actually see anything on the board such as location codes, but if I assume you have a EAY62512801 power supply then the diode is location code D607 and the blue cap is location code C603
Good luck!

[brucetv]

Re: LG 55LS4500-UD Shutting down

Thanks for the tip. It is the EAY62512801 and I just had a chance to pull the Tcon cover and check the fuse which is showing 11.97 on both sides. I'm checking the bone pile right now, it looks like the blue mylar is 222k(not sure the kv yet) and the diode looks like a MUR460G 600v 4A Ultra fast which I buy from mouser part # 863-MUR460G. I'll pull em both in the morning and let you know. Love this forum!

[Nick's Tvs]

Re: LG 55LS4500-UD Shutting down

Your T-con is fine, I can't imagine it being bad in this scenario. That is correct on the type of components, the MUR460G is very difficult to find for sale, I could not find it available for sale, and had to buy an equivalent from china. But you if you have a bone yard of Power supplies, look for LG power supply boards and some Samsung boards also use this ultra fast switch diode. It is possible only the cap is bad however, and also possible only the diode is bad. Either way you need to check them for shorts, and if you do find a short you will need to de-solder one or both of those out of circuit and with your ohm meter check them for shorts. If you do find one to be short, make sure that the circuit board is no longer showing a short and that indeed the source of the issue was only the component you pulled out. This is just to make sure you don't have additional damage else where.
Let us know how this goes.

[johnboy1313]

Re: LG 55LS4500-UD Shutting down

It's highly probable that you have one or more failed LEDs inside the panel. Your PSU is probably OK if the lights flash. In my experience, the set wouldn't power on at all when that diode was bad.

[budm]

Re: LG 55LS4500-UD Shutting down

If those PFC Diode shorted out then you will only have 160VDC between the two legs of the main filter cap, so check and see if you have close to 400VDC between the two legs of the main filter cap or not when TV is turned on.

[brucetv]

Re: LG 55LS4500-UD Shutting down

Okay, got a chance to get back on this LG and budm I'm getting 399VDC on the Filter Cap which are rated at 450v at 82uf. I pulled a leg on the Diode(D607) and it showed good at 0.454 and replaced the blue cap(C603) rated at 221K at 1kv. I was hoping Nick was right but unfortunately the LG is still showing the same exact symptom. I think your right johnboy, we might have a bad led problem. I didn't find any shorts on the power supply so my next step is to get a meter on the leds 1-6 and 7-12. What should I expect to see at startup and what kind of drop should I expect at startup? I noticed the model description say's Edge so I'm assuming this is a edge lit led Tv? Have mercy on me if I have to pull a panel even if I can find the led strip...ugh. Thanks everyone.

[budm]

Re: LG 55LS4500-UD Shutting down

Okay, got a chance to get back on this LG and budm I'm getting 399VDC on the Filter Cap which are rated at 450v at 82uf. I pulled a leg on the Diode(D607) and it showed good at 0.454 and replaced the blue cap(C603) rated at 221K at 1kv. I was hoping Nick was right but unfortunately the LG is still showing the same exact symptom. I think your right johnboy, we might have a bad led problem. I didn't find any shorts on the power supply so my next step is to get a meter on the leds 1-6 and 7-12. What should I expect to see at startup and what kind of drop should I expect at startup? I noticed the model description say's Edge so I'm assuming this is a edge lit led Tv? Have mercy on me if I have to pull a panel even if I can find the led strip...ugh. Thanks everyone.

You are getting the PFC Boosted Voltage so the those diodes and the PFC circuits are fine.

[budm]

Re: LG 55LS4500-UD Shutting down

You have 12 strings of LEDs VC_1~VC_12
The LED+ is the boosted Voltage feeding the Anodes of the LED strings, the VC_1~VC_12 are the Cathode return for the LED strings.
So put the black probe on the chassis, then put the Red probe on the VC_1 then turn on the TV and keep and eye on the meter to see how high the Voltage will go up to and how low it will settle down after 3~4 seconds, record the reading, then do the same for the VC_2~VC_12.
Pictures provided by shopjimmy.
LG EAY62512801 (PLDK-L102A) Power Supply / LED Board
http://www.shopjimmy.com/lg-eay62512...led-board.htm#

[brucetv]

Re: LG 55LS4500-UD Shutting down

Wow....this is strange. Real oddball readings
plugged in v1 71.43 power up 83.71
v2 25.4 11.01
v3 27.49 10.75
v4 26.01 10.075
v5 26.06 10.44
v6 27.10 10.31
v7 25.25 10.5
v8 24.92 11.03
v9 24.87 11.07
v10 24.68 11.03
v11 24.62 10.3
v12 0.003 0.003
Most of them are lower at power up, instead of higher. Only v1 tested normal. Not a good sign. Do edge lit Tv's fail as often as the backlit strip Tv's?

[budm]

Re: LG 55LS4500-UD Shutting down

That is normal for the Return (each return pin goes to the PWM controlled power MOSFET and the current sensing resistor to GND) pin to show higher Voltage at startup because the LEDs will be driven at low current start up.
You do have problem on V_1 (shorts, big doubt on this one, may be you are on the wrong pin) and V_12 (open).
BTW, are you sure that is what you are getting at V_1? You count the pins correctly?
Connector P202 (Black dot = pin 1)
Pin 6 is the V_1,
Pin 7 is N/C
Pin 8 is LED+

[brucetv]

Re: LG 55LS4500-UD Shutting down

Bummer. I was hoping it was the diode and cap and march this tv back to them so they can sell it and give a lot of groceries to the poor. This might be a good test Tv for our new led tester coming in. Shopjimmy is selling these now(has a youtube video too) because we are all seeing a ton of newer Tv's coming in with backlight issue's. LG's especially. It's the SID Model GJ2C and it can power up the led strips or each led individually. It has a built in power supply to power them up safely. I pulled the led cable back and it has 8 contacts. + nc vc12 vc11 vc10 vc10 vc9 vc8 vc 7 so I'm guessing that I can put the SID + lead on the + on the connector and then the negative on each vc to see if it power up the strip. Has anybody used one of these yet? It should be in Saturday and will let everyone know with pictures. Do I skip the nc pin?

[budm]

Re: LG 55LS4500-UD Shutting down

Same tester as this:
https://www.badcaps.net/forum/showth...ght=led+tester
Skip the NC (NO CONNECTION) pin.

[brucetv]

Re: LG 55LS4500-UD Shutting down

Thanks LG...you really suck. Turns out to be a edge lit Tv and the led's are incorporated into the panel! I got the new led tester in today and it confirmed that the led's are burned out on the right hand side. I pulled the led connector back after unplugging from the power supply and taped them down so I could test the led's with the SID. It got up to about 62 volts before the led's would barely light up so it seems there is a bad led pulling the rest of the led's down and that's what's causing the power supply to shut down. And with them unplugged you can turn on the Tv and see the image with the flashlight test. It's bad enough to have to get to back lit led's under the panel and then some idiot engineer thought to incorporate them into the panel at $1450 with a $500 core refund. Screeeewwwww yoooouuuu! I'll pull the boards, sell them on ebay, and donate the the proceeds back to the thrift store. Thanks for all the help forum....it was a learning experience. The LG LN Series are the worst.

[Nick's Tvs]

Re: LG 55LS4500-UD Shutting down

Could you please post pictures on these strips, I do believe there is a way to remove them and get them fixed.