42LK450-UB Noob question

[nomoresonys]

Re: 42LK450-UB Noob question

Does not apply.

[budm]

Re: 42LK450-UB Noob question

Will the TV still power cycle if you do have the inverter board connected to the power supply board?
Do you still have all your original boards?

[nomoresonys]

Re: 42LK450-UB Noob question

Does not apply.

[will62]

Re: 42LK450-UB Noob question

Before you bypassed the main board, it was receiving an error signal from the inverter board, and controlling both the power supply and the inverter board. The main board may have been attempting resets to correct the problem. You may have seen the picture come on 4 times, because that is the limit of reset attempts before complete shutdown.

Now, with the main disconnected, the driver IC on the inverter board has it's own protection circuit. It monitors for over/under voltage and current. One bad lamp will shut it down just as quickly as a bad component on the board. If there is no current flow due to a bad lamp, it could also be due to a loose wire/connector, hanging there with ~1000V going to it. Not something that you would want to leave on.

Also, as I mentioned in a previous post, the inverter board may need the A-dim and P-dim signals to start. While you're waiting on the new board, you may want to put resistor jumpers on those just to see if anything changes.

Edit: some good info from nomoresonys as I was posting this

[nomoresonys]

Re: 42LK450-UB Noob question

Does not apply.

[budm]

Re: 42LK450-UB Noob question

It can be a little confusing, watch the whole thing, be careful he does inform that there's about 1000 volts, having done all the testing he did in the video, what solved my issue was the ground out test at 16 minutes into the video, I believe he added the extra leads because it took so long for his tv to shut off, yours is going out fast so you just need to ground out each transformer til the backlights stay on, if you find one that makes them stay on, then you found a faulty transformer or ccfl/lamp. he does a bypass which I did, word of advice if you're a bad solderer like me, better practice first, the pads are small and close together. Keep in mind these are two different brands, there may be some differences.

OP's TV does not have Balancer board like the TV I helped you fix, this one has the Inverter board separated from the power supply board, the one you did the bypass on the Balancer board has power supply-inverter board combo and the Balancer board.
So DO NOT TRY TO BYPASS ANYTHING in this OP Inverter board!

[nomoresonys]

Re: 42LK450-UB Noob question

OP's TV does not have Balancer board like the TV I helped you fix, this one has the Inverter board separated from the power supply board, the one you did the bypass on the Balancer board has power supply-inverter board combo and the Balancer board.
So DO NOT TRY TO BYPASS ANYTHING in this OP Inverter board!

Oh crap my bad, sorry bout that, disregard, will edit.

[newkidontheblock]

Re: 42LK450-UB Noob question

OP's TV does not have Balancer board like the TV I helped you fix, this one has the Inverter board separated from the power supply board, the one you did the bypass on the Balancer board has power supply-inverter board combo and the Balancer board.
So DO NOT TRY TO BYPASS ANYTHING in this OP Inverter board!

Thanks for the heads up. I was watching the video and they have the combo board. I figured I didnt even want to go down that road.

[newkidontheblock]

Re: 42LK450-UB Noob question

Also, as I mentioned in a previous post, the inverter board may need the A-dim and P-dim signals to start. While you're waiting on the new board, you may want to put resistor jumpers on those just to see if anything changes.

Edit: some good info from nomoresonys as I was posting this

I did try with a jumper on the A-dim and P-dim as well to see if the results change. The test yielded the same results both times.

[newkidontheblock]

Re: 42LK450-UB Noob question

Will the TV still power cycle if you do have the inverter board connected to the power supply board?
Do you still have all your original boards?

The only thing that was connected to the power supply while I did the test was the inverter board. The main board was dissconnected (as well as the controls like volume and what not because that was attached to the main board) and the T-conn board gets its power from the main board as well. So only the power supply and the inverter board were the only things attached.

And yes, I do have all the original boards. I intend on doing these tests on them as well when i get it working to sell later. Why do you ask?

[budm]

Re: 42LK450-UB Noob question

Try it with every thing connected except the Inverter board to see if the TV will still cycling or not, if it does then you will have to simulate the error signal pin.

[newkidontheblock]

Re: 42LK450-UB Noob question

Try it with every thing connected except the Inverter board to see if the TV will still cycling or not, if it does then you will have to simulate the error signal pin.

So before i unplugged the inverter only, i checked to see what the tv did. The power button will pulse to blue about 3 times, then fade to red meaning the TV was off. Then, i unplugged the inverter and put the main board back on, and it did the same thing. Doing this made me think it is not the inverter at fault here.


AND i was right. Changed to the new inverter, problem is still there....
now that i am all discouraged, any other ideas? There seems to be nothing else that would cause this issue to me. TV still did it with main board attached or detached, same as inverter. Im lost now.

Thanks for all your help so far.

[budm]

Re: 42LK450-UB Noob question

So before i unplugged the inverter only, i checked to see what the tv did. The power button will pulse to blue about 3 times, then fade to red meaning the TV was off. Then, i unplugged the inverter and put the main board back on, and it did the same thing. Doing this made me think it is not the inverter at fault here.


AND i was right. Changed to the new inverter, problem is still there....
now that i am all discouraged, any other ideas? There seems to be nothing else that would cause this issue to me. TV still did it with main board attached or detached, same as inverter. Im lost now.

Thanks for all your help so far.

OK, That is what I am trying to find out what the TV will do if the Inverter board is not connected, and that is why I indicated that you may have to pull the INVERTER ERROR signal pin LOW or pull it HIGH to see how the TV will react. The main board is looking at that error signal from inverter board (which we have it disconnected) to see if the TV should go into shut down or stay on. Right now we do not know if it is looking for LOW signal to indicate that the inverter is OK or if it is looking for HIGH signal to indicate that the inverter is OK.

[will62]

Re: 42LK450-UB Noob question

Budm, look back at the troubleshooting chart on post #7. Main is looking for a low signal on error pin.

[newkidontheblock]

Re: 42LK450-UB Noob question

well when the inverter board was disconnected, the tv did the same thing it always did. Cycle a few times and then shut off. So, even with the inverter board disconnected it still just shuts down after about 10 seconds. So what would you like me to do? I know it says to pull the inverter error signal pin, but you mean just pull it out of the harness? im really sorry.

[will62]

Re: 42LK450-UB Noob question

Can you leave the main connector on, and put a resistor in from the back (where the wires go into the connector) from error to ground?

[newkidontheblock]

Re: 42LK450-UB Noob question

with the inverter board connected as well or no?

[budm]

Re: 42LK450-UB Noob question

Can you leave the main connector on, and put a resistor in from the back (where the wires go into the connector) from error to ground?

+1, use 100 Ohms resistor for pull-down to simulate LOW signal to see what will happen, if it is still cycling then remove the 100 Ohms resistor and then use 1K resistor between that same Error pin and 5VSTBY to simulate HIGH signal and see what will happen.

[budm]

Re: 42LK450-UB Noob question

with the inverter board connected as well or no?

No INVERTER BOARD connected, we are simulating the signal with resistor.

[newkidontheblock]

Re: 42LK450-UB Noob question

+1, use 100 Ohms resistor for pull-down to simulate LOW signal to see what will happen, if it is still cycling then remove the 100 Ohms resistor and then use 1K resistor between that same Error pin and 5VSTBY to simulate HIGH signal and see what will happen.

Disconnected inverter board but I did not have any 100 ohms resistors near buy. RIP Radio Shack. I took a 1k and put it on the Error and Ground of the power supply while everything else is connected and the TV stayed on. I left it sit for about 40 seconds then removed the resistor and the TV instantly turned off on its own.

What now?