LG 65UH5500-UA Backlight flash on first power up only

[jason123]

Re: LG 65UH5500-UA Backlight flash on first power up only

Glad to hear it worked.

I am in disbelief... very glad it worked. Thanks

[jason123]

Re: LG 65UH5500-UA Backlight flash on first power up only

Thanks Diah. Nothing seems to need an update. Software is connecting to server and downloads correctly. Thanks

[nomoresonys]

Re: LG 65UH5500-UA Backlight flash on first power up only

Glad to hear it worked.

[Diah]

Re: LG 65UH5500-UA Backlight flash on first power up only

with service remote or apk on android if you use (E-Z adjust) and (IN_Start) you can change the version of size / serial no / and other stuff to match the original info which printed on the back cover of the set... in order to connect correct to LG server update and smart server

[jason123]

Re: LG 65UH5500-UA Backlight flash on first power up only

Thanks... just got the board and it seems to work beautifully.. when i look in Settings it says TV is UH5500...seems all firmware is the same as you stated for the UH5500... Oddly people on ebay are selling the 65UH5500 for higher price than the 50UH5500

[nomoresonys]

Re: LG 65UH5500-UA Backlight flash on first power up only

Now looking at the reference guide here, it does appear that they use the same firmware but I did not see anywhere while looking at boards from various sites where they will interchange: https://www.lg.com/us/support/product/lg-65UH5500.AUSQ

[nomoresonys]

Re: LG 65UH5500-UA Backlight flash on first power up only

If that is your board, then your board number is EBR82959601, the other numbers are generic numbers, board gets populated, board gets sticker, the number is on the sticker, minus EBR : https://www.shopjimmy.com/lg-ebr8295...-ua-cusjlh.htm

[jason123]

Re: LG 65UH5500-UA Backlight flash on first power up only

So given that there maybe issues with the main board, I wanted to replace it (since I am vested in this TV - ), but the same part number board (EAX66958003(1.1)) seems to be used also on 50UH5500

Does anyone know if the 50UH5500 board would work in this 65" TV?
I couldn't find firmware to flash the main board if needed, or do I need to change something in the service menu?

[budm]

Re: LG 65UH5500-UA Backlight flash on first power up only

OK, I read page 11 and 12, the IC has internal pull-up circuit for pin 22 to start the IC, you then pull it down when you want to disable the IC.
So basically, this board the PFC/HBC are always running.

[jason123]

Re: LG 65UH5500-UA Backlight flash on first power up only

So after several attempts at finding what else that pin 22 is connected to, I took the IC off the board again (hopefully no major damage!) and sure enough, that pin 22 (unless I'm counting incorrectly) is "ONLY" tied to that cap (Used for soft start mode only) - I don't see a way it's connected to an opto / enable function.

What am I missing?

[budm]

Re: LG 65UH5500-UA Backlight flash on first power up only

https://www.badcaps.net/forum/attach...1&d=1576726423
1.2V = Enable PFC only
2.2V = Enable PFC + HBC
BTW, If that pin is connected to anything then it should not change state.

[jason123]

Re: LG 65UH5500-UA Backlight flash on first power up only

Section 7.8.8.1 (page 26) explains the function of this pin when used as soft start. I think the voltages i am reading are as intended. Don't you think?

[budm]

Re: LG 65UH5500-UA Backlight flash on first power up only

Pin 22 is the ENABLE pin so it has to be controlled some how, and it does change state, but I cannot see how the control Voltage, 5.53V/8.6V can be that high either..
At this point you will have to find the schematic to really find out what is going on.

[jason123]

Re: LG 65UH5500-UA Backlight flash on first power up only

Both measurements are referenced to hot gnd. First reading was pin 22 references to the pad the capacitor is connected to, which is shorted to negative lead of large cap. Second measurement to confirm for you was pin22 referenced to negative lead of large cap.
I tried continuity check between pin 22 and the traces exiting top and bottom of chip and there doesn't seem to be a connection

[budm]

Re: LG 65UH5500-UA Backlight flash on first power up only

It's page 34 (see my post #40).
Enable input (pin SSHBC/EN).
There may be trace going under the IC.
I cannot see how you can have the same Voltage readings using the chassis GND and using the Hot side ground.

[jason123]

Re: LG 65UH5500-UA Backlight flash on first power up only

So not the cleanest solder job...but pin 22 connects to cap then to hot gnd, so i soldered across the cap. Just measured again from pin 22 referenced to large cap gnd and same results.

I see what you're referring to on page 34.. table 5 on page 32 lists range for that pin as -1.4 to 12 v..(abs max maybe)...used in a different mode? This pin doesn't seem to be driven by a voltage.. just has a cap to hot gnd?

[budm]

Re: LG 65UH5500-UA Backlight flash on first power up only

Pin 22 of the PFC IC reads 5.53 V when TV is off.. jumps to 8.6 when it's turned on.

That must be measurement error. Did you use the chassis as the GND for the meter? You need to use the negative leg of the main filter cap as the ground for the meter because you are making measurement in the hot side.
See spec sheet of the IC on the page that I pointed out to for what the Voltage should be on pin 22.

[jason123]

Re: LG 65UH5500-UA Backlight flash on first power up only

Pin 22 of the PFC IC reads 5.53 V when TV is off.. jumps to 8.6 when it's turned on.

[budm]

Re: LG 65UH5500-UA Backlight flash on first power up only

P-DIM must be present since the backlights are on and you can dim the backlights at this point.
The PFC circuit, need to look at pin 22 of the SMPS/PFC IC as suggested.

[jason123]

Re: LG 65UH5500-UA Backlight flash on first power up only

P-DIM is pin 12 and is not accessible - I'll get a pair of sharper tip leads and report shortly.
C409 reads 88.x V

Traced DRV-ON back to the motherboard - seems something has changed, either resistors changed value from nominal (not labeled - 603 package) or leakage in the path is higher, but the main board generates 3.3 V, but after resistor networks by the time it gets to the LED Driver Pin 2 of OZ9906 (Chip Enable) it's down to 1.5 V - not sufficient "ON" logic.. given that I don't have 603 resistors and I can't see the darn things anyway, I replaced one of the series resistors (there are several between the main board and the LED Driver) with a blob of solder and that did the trick.. so far so good.. LED Driver is seeing 2.9 V on the EN pin of the controller - Backlight comes on..

Now.. back to the weird problem that appeared on 2 power supply boards - why are the large caps seeing 385V always... PFC not operational on 2 boards ??? very odd