Thanks for all your help
spurf
Member
Last Activity: 05-14-2022, 04:43 AM
Joined: 04-08-2022
Location: Newcastle, NSW
-
Re: LG 65UH652T won't turn on
Thanks for all your help
-
Re: LG 65UH652T won't turn on
The board finally arrived and the TV works! I tested out the original mainboard and that still works despite baking it in the oven
Leave a comment:
-
Re: LG 65UH652T won't turn on
Well I was a bit careless and managed to create a short on Q601 which blew it and the main fuse. I decided to give up but found a replacement board with a later revision on eBay and will see how I go. Thanks for all the help and will update once I install itLeave a comment:
-
Re: LG 65UH652T won't turn on
I get a fluctuating voltage between 37 to 38 AC and 0.6 and 1.8V DC
Testing both of them out-of-circuit the LCR-T4 identifies both of them as an N-E-MOS with C=1.97nF and Vt=3.3V...Leave a comment:
-
Re: LG 65UH652T won't turn on
Sadly Q601 and 602 test fine ☹Leave a comment:
-
Re: LG 65UH652T won't turn on
I've tried this (see my earlier post) and the voltages are not stable when the board is powered up with the jig. I'll test Q601 and 602 like you suggested. What is the best way to remove the white gunk? R100 tests fine...Leave a comment:
-
Re: LG 65UH652T won't turn on
I have tried powering the TV with the backlight disconnected and it exhibits the same behaviour. Does this exclude the backlights or do LGs refuse to boot up if the backlight is not connected?...Leave a comment:
-
Re: LG 65UH652T won't turn on
I picked up an LCR-T4 meter off eBay and have tested all the capacitors out of circuit and they all have capacities that correspond to their rating and have low ESRs except for the large capacitor. It's a 460V 120uF and has an ESR of 1 ohm at room temp. If I warm it up to 80 degrees celcius it drops to 0.6 ohms. I have tried warming it in circuit but the TV still doesn't power up. I'm unconvinced that this is the cause as if the capacitor was slowly degrading I don't see how it would work perfectly and then completely stop working.
I'm...Leave a comment:
-
Re: LG 65UH652T won't turn on
I'm a bit stumped on what could be causing the the AC fluctuations on the lines that should be DC.
Does anyone have any idea which component(s) that would be malfunctioning to cause this?Leave a comment:
-
Re: LG 65UH652T won't turn on
Here are the two controllers. I can't make out much on the square one unfortunately and this is the best photo I managed to get....Leave a comment:
-
Re: LG 65UH652T won't turn on
I do have voltage on both the LED and 13V lines but they aren't stable. They start off below spec but rise to approximately the correct values if I use the 3V jig but they aren't stable.
The DC voltage on the large main capacitor fluctuates from 391.1 - 391.6 V DC and doesn't change when I press the power button.
What is the safest way to remove the lacquer? Scrape or solvent?...Leave a comment:
-
Re: LG 65UH652T won't turn on
Trying to get a quantitative read on why the voltage is so unstable. I had retested in DC but got the same readings as I had in my opening post....Leave a comment:
-
Re: LG 65UH652T won't turn on
Retested this morning and the voltages are unchanged whether the black and white LED cables are connected or not. There seems to be a substantial amount of AC on the LED+ and 13.2V lines. It is present with or without the jig.
Here is a video testing the 13.2V line with the jig....Leave a comment:
-
Re: LG 65UH652T won't turn on
Oh I see. That one is IC100. Even harder to make out due to thicker globs of lacquer:...Leave a comment:
-
Re: LG 65UH652T won't turn on
It's hard to make out as it's covered in some sort of lacquer. Here is a photo:...Leave a comment:
-
Re: LG 65UH652T won't turn on
ic801...Leave a comment:
-
Re: LG 65UH652T won't turn on
I baked the original mainboard not the replacement. If I can get the TV to power up I'll retest the old board to see if it still works...Leave a comment:
-
Re: LG 65UH652T won't turn on
Sorry for the noob question but how do you test the backlights? Also, the TV behaves the same even when the black and white leads are disconnected from the power board, i.e. a brief blink of the red LED and the power consumption doesn't shift from 1W. Does this make the backlights unlikely to be the issue?...Leave a comment:
-
Re: LG 65UH652T won't turn on
Are you talking about the little ones on the top right? I tried the hair-dryer already but not sure if I got them hot enough. Do you know what temperature we are aiming for as I have an IR thermometer to measure. I've checked the diodes and they all have ~0.5v drop across them...Leave a comment:
-
LG 65UH652T won't turn on
I have had this TV for nearly 6 years from new. It has been connected to a smart powerboard the whole time so the power to the TV is turned off when the AV Receiver turns off. Was working fine one day and then the following day wouldn't power on. The red standby LED lights up but when I press power on the remote or manually the red LED turns off after a second or so and then comes straight back on. I've connected the TV to a power meter and the TV is only drawing ~1W even after the power button is pressed so not much is happening.
I took off the back and was hoping to find an obvious...
No activity results to display
Leave a comment: