42LK450-UB Noob question

[newkidontheblock]

Re: 42LK450-UB Noob question

Really hard to see, my guess. Part number would be
tz.6502x101 B6fy01-03

Piccs

[budm]

Re: 42LK450-UB Noob question

There are two fuses for two section of the inverter circuits, did you verify that BOTH of them are OK?

[will62]

Re: 42LK450-UB Noob question

It may also be useful to remove the main board shut-down so that you can further troubleshoot the inverter board problem. You can remove the connector from the main board, and use resistors to jump power as shown in the diagram below. I'm not sure if you'll need to jump power to A-dim and P-dim as well, you can try w/o first. You might want to use a power strip, so that you can turn power on and off quickly, without having to plug/unplug.

After you have all the required jumpers in place, the backlight should come on as soon as you power up. It may be an over current problem causing the shut-down, so you don't want to leave them on too long.

[budm]

Re: 42LK450-UB Noob question

https://www.badcaps.net/forum/attach...4&d=1518882273
So after the backlights flash on and go dark, the those Voltages (main board connected) are still the same?

[newkidontheblock]

Re: 42LK450-UB Noob question

There are two fuses for two section of the inverter circuits, did you verify that BOTH of them are OK?

Testing both fuses. Both in AC and DC (because im not sure which on it would be)
In DC, both stayed below .030 both with the TV on or off

In AC, both spiked to .525, but thats it. The fuses on the board say 125v, but i didnt get nearly that.

[newkidontheblock]

Re: 42LK450-UB Noob question

https://www.badcaps.net/forum/attach...4&d=1518882273
So after the backlights flash on and go dark, the those Voltages (main board connected) are still the same?

Yes, I tested each fuse while the tv was going in and out. They remained at the listed numbers the entire process

[budm]

Re: 42LK450-UB Noob question

https://www.badcaps.net/forum/attach...882273</i></b>
We are dealing with DC so you should see 24V DC at each end of the fuse with ref. to GND when TV is ON, the same way you check the Voltages on the connector's pins.

Yes, I tested each fuse while the tv was going in and out. They remained at the listed numbers the entire process

It cannot be 0 V dv because you said the Voltage remain the same (24V is present as shown in your chart when TV is ON) when the backlights go out.
If all the control signals and the Voltages remain the same (TV ON Voltage chart) after the backlights go out then you will be looking at the inverter board or the lamp, so check the inverter transformer high Voltage secondary winding of each transformer to see if the resistance are within 3 % from each other or not first as suggested, but make sure the fuses are good first.
You need to really clarify as to what you mean by the Voltages remain the same (after the backlights go out) as in TV is on Voltage chart or TV OFF Voltage chart.
So the bottom line for the Voltage reading:
1) The Voltage chart when TV is OFF is as shown in your chart #1 (TV OFF Voltage chart)
2) TV is turned on and it has Voltages as shown on chart #2 (TV ON Voltage chart)
3) What are the Voltages AFTER the backlights go off? Chart #1 or chart #2?
Right now it sounds like it goes back to Voltage chart #1 after the backlights go out.

[newkidontheblock]

Re: 42LK450-UB Noob question

Ok, so by voltages stay the same i meant that when the screen is on, the voltages jumped. But as the backlight went out, the voltages either dropped imediately, or progressed to zero (as in losing power). They would jump back up as the backlight would kick on. The bottom half of my voltage chart on jumped to 24v, but stayed there even when the backlight went out. The 12v's up top as well as the 2 DIM wires jumped with the backlight, as did the ERROR wire. Oddly enough, the ERROR wire would be at around 1.2 while the backlight was on, but then jump to the 2.9/3.0 as per the chart. Then, it would fall to zero when the TV would turn itself off after the standard 4 attempts.a

[budm]

Re: 42LK450-UB Noob question

OK, I re-read you reply over and over again, so it sounds like it goes into on/off loop about 4 times that is why the switched 12VDC and switched 24VDC come and go, correct?
If that is the case then do as suggested in post #23.

[newkidontheblock]

Re: 42LK450-UB Noob question

OK, I re-read you reply over and over again, so it sounds like it goes into on/off loop about 4 times that is why the switched 12VDC and switched 24VDC come and go, correct?
If that is the case then do as suggested in post #23.

Ok, so i will get ahold of some 1k resistors and jump to get the backlight to come on and stay on. When i get this done, what will it tell me? Is the point of this just to test the backlight inverter? Obviously its kind of hard to test anything that gets power when it keeps powering back off.

[budm]

Re: 42LK450-UB Noob question

If the backlights stay on then it means the power supply board, inverter board, and lamps are good.
You must do the test WITHOUT the main board connected, the backlights should come on right away when you plug the power cord into the AC outlet and stay on as long as the power cord is plugged in.

[newkidontheblock]

Re: 42LK450-UB Noob question

Ok, sorry for the delay. I have no electronic hobby stores near me at all so i had to get resistors shipped in........

So i jumped the pins on the opposite end of the connector from the power supply (just unhooked it from the main board and added resistors where needed, while not having the main board attached to anything)

The screen will come on for about 2 seconds then turn off again never to come on again until i pull power away and give it back (toggle the surge protector)

So if what im reading is correct, I have myself a bad inverter board? ill send a pic of the jump so you see what i did, to make sure its correct.

[will62]

Re: 42LK450-UB Noob question

You've got a 50-50 chance that it is the inverter board, and not a bad lamp. Do you want to go ahead and order a new board, or keep troubleshooting the shutdown?

[newkidontheblock]

Re: 42LK450-UB Noob question

Well like I said its only like $25, so its not the end of the world. I just wanted to be sure not to keep throwing money at it.

Now on a follow up question, you are not the first person to mention a lamp. While i may be ignorant, what do you mean? I keep thinking the only TV's with the actual bulb in it, but what "lamp" would this tv have?

Thanks again

[will62]

Re: 42LK450-UB Noob question

CCFL lamps or bulbs.

[vinceroger69]

Re: 42LK450-UB Noob question

Well like I said its only like $25, so its not the end of the world. I just wanted to be sure not to keep throwing money at it.

Now on a follow up question, you are not the first person to mention a lamp. While i may be ignorant, what do you mean? I keep thinking the only TV's with the actual bulb in it, but what "lamp" would this tv have?

Thanks again

some older lcd tvs like yours use ccfl tubes like in this ebay add
https://www.ebay.co.uk/itm/32-LG-LCD...IAAOSwO7haOwuD

your set could have a failed invertor board a bad ccfl tube or even a bad tube holder i would try a invertor board next if this was my set (you can always re sell it it fails too fix your set) as to get too the ccfls you need to remove the lcd panel and as these are fragile high risk of cracking/damaging it.

[budm]

Re: 42LK450-UB Noob question

Well like I said its only like $25, so its not the end of the world. I just wanted to be sure not to keep throwing money at it.

Now on a follow up question, you are not the first person to mention a lamp. While i may be ignorant, what do you mean? I keep thinking the only TV's with the actual bulb in it, but what "lamp" would this tv have?

Thanks again

https://www.ccflwarehouse.com/

https://www.youtube.com/watch?v=EO2gHBJCvH0

[newkidontheblock]

Re: 42LK450-UB Noob question

Now while the screen was out, i did do the flashlight to make sure it wasnt just the light itself going out. There was no picture while the screen went off, like it legitimately just turned off and back on four times. So I dont think it is the bulbs themselves or the picture would still be visible without the light right?

Also, how would a bulb being out cause the whole screen to go out? Being as the picture would actually go out entirely versus just the light, that is why i was leaning on the main board. But when i did the resistor test, the screen was only fine for a few seconds before it kicked out.

Am i missing something?

[nomoresonys]

Re: 42LK450-UB Noob question

http://www.shopjimmy.com/auo-19-42t1...t-inverter.htm My first thought is maybe one or more of the capacitors on the inverter is bad, hard to tell without testing.

[nomoresonys]

Re: 42LK450-UB Noob question

Now while the screen was out, i did do the flashlight to make sure it wasnt just the light itself going out. There was no picture while the screen went off, like it legitimately just turned off and back on four times. So I dont think it is the bulbs themselves or the picture would still be visible without the light right?

Also, how would a bulb being out cause the whole screen to go out? Being as the picture would actually go out entirely versus just the light, that is why i was leaning on the main board. But when i did the resistor test, the screen was only fine for a few seconds before it kicked out.

Am i missing something?

Tv's have protection shut down, when it detects fault it shuts down for safety and to prevent further damage, fire etc. like a bad ccfl/lamp for example, will shut it down.