New power supply, but tv fails to power on.

[Glitcher]

Re: New power supply, but tv fails to power on.

Wait so you have replaced the PSU already and it still has the same problem correct?
And you have the 5V output from the PSU but still no red standby LED light?

[Marzog]

Re: New power supply, but tv fails to power on.

Wait so you have replaced the PSU already and it still has the same problem correct?
And you have the 5V output from the PSU but still no red standby LED light?

That's correct. Granted, I was able to check the standby voltage without the power supply connected to the main board. With the main board connected, disconnected, or with a 1k resistor in place between pins 1&3, still no led light. As far as I could see at least.

[Glitcher]

Re: New power supply, but tv fails to power on.

I would say that your main board is probably bad.

[Marzog]

Re: New power supply, but tv fails to power on.

I would say that your main board is probably bad.

Aye. Based on what others have been saying, I'm leaning towards that conclusion as well. But before I spend the $65 for a new main board, is there any possible way to work around whatever the faulty part is?

For example, if the audio chip is the culprit, is there a way to work around it? If it helps I will likely be using this tv as a second monitor for my laptop, so sound wouldn't be needed. Not sure if it's possible to do this, but just thought I'd ask.

[Caleb]

Re: New power supply, but tv fails to power on.

You can check resistances across each of the power pins of main board to ground screw. I think the standby supply is likely the one in trouble, if it test low ohms you can try unplugging harness to button board and see if your lucky enough to have trouble on it rather than the main. While it is possible many times to repair a main board it is probably overly ambitious for your first repair, even the experienced techs have relatively low success rates on component level repair of main boards.

If your still wanting to try and find the culprit you can try to rig a current limited power source up across the short circuit and see which components heat up first

[Marzog]

Re: New power supply, but tv fails to power on.

Tested all the pins using one multimeter prong, with the other on ground screw. Multimeter was set on Ohms (200).

Here are the results:
1: 1
2: 1
3: 1
4: 0.6
5: 0.6
6: 0.6
7: 1
8: 1
9: 0.6
10: 0.6
11: 0.6
12: 0.9
13: 1
14: 1
15: 1
16: 1
17: 0.6
18: 0.6
19: 1
20: 0.6
21: 1
22: 1
23: 1
24: 1

[budm]

Re: New power supply, but tv fails to power on.

Is that '1' for 1 Ohm, '0.6' for 0.6 Ohm? They do not look right, it can't have 1 and 0.6 Ohm on that many pins.
Are there labels for each one of those pins?

[Marzog]

Re: New power supply, but tv fails to power on.

The multi meter simply said 0.6 on most pins. If it didn't have a reading, it just showed
1----.- where '-' designates a blank space.

And each pin has a label as far as I can tell.

The attached picture below indicates which pin is which as far as I can see.

[budm]

Re: New power supply, but tv fails to power on.

OK, '1' = over range.
And those that show 0.6 are the ground pin,
Other pins are not showing low resistance, so it can be active shorts that will not show up until power is apply.

[Marzog]

Re: New power supply, but tv fails to power on.

How will I measure them with the power on? I checked the same ions with the power on, and the only difference was the ground pins read 1.1-0.9. The rest were over range. Is there where I'll need the 1k resistor and some small wires?

[Caleb]

Re: New power supply, but tv fails to power on.

Just to be clear (you posted the power board pic) you were testing for shorts on the main board correct? If so the short is beyond a switching component and will only be presented to the power board when it is switched on. You wont be able to measure resistance with the board on, you could put your meter into current mode and check for current draw, standby should draw less than an amp. That makes it very difficult to locate, the only way Ive been able to find one like this is by applying an alternate power source to the shorted circuit and waiting for the component to get hot.

If you want to try that you will need a current source preferably 5v limited to no more than 800ma. You will have to pull the affected circuit out of the wiring harness on the power board and add in your current source in a minute or so the bad component should get quite warm.

[Marzog]

Re: New power supply, but tv fails to power on.

Just tested with the main filter cap (CP815) with the main board attached. If I'm reading the multimeter correctly (I had it set to DCV 1000) it read between 245-265. I attached a picture of the setting I had the multi meter on.

[Marzog]

Re: New power supply, but tv fails to power on.

Did two follow up readings on the main filter cap. Multimeter was on same setting as in the previous post.

Without main board attached and no resistor but no resistor: 165
Without main board attached and WITH a 1k resistor jumping pins 1&3: 390

As you can guess by now, I'm very inexperienced with electricity and how circuit boards functions and all that. Any ideas what these readings mean? Assuming I read them right in the first place.

[budm]

Re: New power supply, but tv fails to power on.

"Without main board attached and WITH a 1k resistor jumping pins 1&3: 390" that means the PFC Voltage circuit is working fine.

[Marzog]

Re: New power supply, but tv fails to power on.

"Without main board attached and WITH a 1k resistor jumping pins 1&3: 390" that means the PFC Voltage circuit is working fine.

Alright. So, what exactly is this pointing to? Does all of this indicate that the main board is indeed at fault? Should I consider getting a replacements in board? Or are there some more tests you'd like me to conduct?

[budm]

Re: New power supply, but tv fails to power on.

At this point I believe your power supply to be OK, I have you put 5 Ohm 5 Watts resistor load on the 5V standby just to be sure that the 5V is steady as in my post 14, but I do not know if you have done that or not.
We also suggest you to put meter in DC Current in line with the 5V STBY output to look at the current draws by the main board.

[Marzog]

Re: New power supply, but tv fails to power on.

How would I apply 5 Ohm 5 Watt resistor load onto the standby?

And how would I test the dc current draw of the main board? Since, measuring what current it draws would require it to be plugged in. And if it's plugged in... I don't know how I'd get a reading from it.

[budm]

Re: New power supply, but tv fails to power on.

"How would I apply 5 Ohm 5 Watt resistor load onto the standby?" You will be running the power supply board by itself, you will connect the resistor between the ground pin and the 5VSTBY pin, then check the voltage on the resistor, it should maintain 5VDC.

To check the current draw you will have the main board connected to the power supply board and, you will have to cut the 5VSTBY wire and put meter in DCA mode and connect each probe to each end of the wires, you basically put the meter in series with the wire. You should read your meter manual and learn how to use it next.

[Marzog]

Re: New power supply, but tv fails to power on.

To check the current draw you will have the main board connected to the power supply board and, you will have to cut the 5VSTBY wire and put meter in DCA mode and connect each probe to each end of the wires, you basically put the meter in series with the wire. You should read your meter manual and learn how to use it next.

Read the owners manual, and followed the instructions for conducting a DC current measurement.

I conducted this test with my multimeter in 10A. I assumed that the 5VSTBY wire is the wire correlated with pin #3, so that's the wire I snipped and tested.

According to my multimeter, the current draw changed with each of those 'tick' sounds.
E.g: it would display 0.38 *tick* 1.59 *tick* 0.51 etc.

As far as I could tell, there was no pattern to the current draw, but it fluctuated between 0.30 and 2.08.

[budm]

Re: New power supply, but tv fails to power on.

This reading is from just having the boards connected but the power switch not activated? 2A is quite a lot for being in standby mode, it is varying because the STBY power supply voltage is going on and off.