Samsung PN43E450 - Won't turn on

[spudnik144]

Hi - this is my first post in this forum.

I have a Samsung PN43E450. It appears dead, no lights, no clicking, nothing at all happens with the power button or remote.

So far I've traced the fault to the main board by disconnecting it and performing the test that grounds some pins on the power board and shorts some points on the logic board. Got a good test display of colors and patterns cycling through. The main board is BN96-24583A.

I'm only getting .06 volts on the pins connected to the power button. there should be 3.3 volts on those pins. The .06 goes to 0 volts when the power button is depressed.

The PS-ON pin on the power board reads 2.35 volts with the main board plugged into it, and 3.66 volts with the main board unplugged. I think 3.66 volts is closer to what it should be. Does this indicate a short somewhere on the main board?

The standby pin reads 5.1 volts.

I've tried tracing the 2.35 volts from the PS-ON pin to other points on the main board. Kind of hard without a schematic. I only get to a point just to the right of the characters "R215" on the upper right hand side of the board. After that any readings in that vicinity are .02 and .06 volts. There are some points that read 5 volts (from the standby pin?).

There's an IC in that area, a Z1051P1. Could there be an issue with that?

Where else would you suggest to take readings on the main board to narrow down the fault? I'd really like to repair this at the component level if possible as opposed to replacing the board.

Any help or hints is much appreciated.

Thanks

[tom66]

Re: Samsung PN43E450 - Won't turn on

[Posted in error - re-read post and see you have done test already. Sorry.]

[spudnik144]

Re: Samsung PN43E450 - Won't turn on

No problem - thanks for replying.

Any ideas on what component may be causing the problem?

[tom66]

Re: Samsung PN43E450 - Won't turn on

It doesn't help you much, but I ended up replacing the main board on a PS51D450 for the same fault. Samsung didn't change much between D and E series PDP. I found a used part for £14.50 (about $25.)

One advantage of swapping the main board is if you can get hold of a PN43E490 main board, and a bluetooth transmitter, you can upgrade your TV to the 3D capable model, if that matters to you. I can confirm this works on the 51" D450.

[MagicSmoke]

Re: Samsung PN43E450 - Won't turn on

Unless your really good at removing and re-soldering tiny SMD components It is easier to replace main board. Just went through this w/ my PN60E550.

Had 5.3v to main board, 3.3v on voltage regulator but it was not making it to the power button control.

Without a schematic of the board it is almost impossible to locate the fault. I replaced the main and now have correct voltage to power button. I know that's not what you want to hear but I could not find a schematic for mine anywhere.

[Agent24]

Re: Samsung PN43E450 - Won't turn on

If the voltage at the power button is low, there could be a shorted debounce capacitor on the power button line, I had that on an LCD monitor once. I have also encountered shorted\leaky buttons too.

[spudnik144]

Re: Samsung PN43E450 - Won't turn on

Thanks everyone for the helpful comments!

I have replaced SMD components before - definitely not an easy task though. If I could identify the faulty component I'd give it a try then replace the board if it didn't work out.

Interesting about upgrading to a 3D capable model. I'll research that further.

I've disconnected the power button and re-checked the voltage at the connector on the board. Still the same low voltage. Do you think it could be some shorted capacitors on the board near this connector?

[Agent24]

Re: Samsung PN43E450 - Won't turn on

Check the resistance across the power button circuit, and see if there a short first

[spudnik144]

Re: Samsung PN43E450 - Won't turn on

Thanks, I'll check for a short across the power button circuit when I get home from work. I'll report back.

[spudnik144]

Re: Samsung PN43E450 - Won't turn on

I've checked all the pins on that 8 pin connector on the main board connected to the power button, with the power button disconnected from the main board. Pins 2 and 3 are shorted, none of the other pins are shorted together. I've looked at a manual and it looks like pin 2 is ground, and pin 3 is 3.3 volts.

Can someone confirm that pin assignment? If that is the case, then this could lead me to where the problem lies.

What do you think?

[tom66]

Re: Samsung PN43E450 - Won't turn on

That does look bad. Could the 3.3V supply on the board be bad? This may be a linear regulator or switching supply.

[Agent24]

Re: Samsung PN43E450 - Won't turn on

Can you put the manual up here or link to it? I couldn't find one easily. Photos may also help.

[spudnik144]

Re: Samsung PN43E450 - Won't turn on

Here's the manual I was referencing.

http://elektrotanya.com/samsung_pn43.../download.html. I know it's not the e450, but I thought the pinout info would at least be the same.

It breaks into several PDF files. I looked at the "05_wiring_diagram". On page 5-5 there's a pinout for CN710 which I took to be the connector I've been testing.

[spudnik144]

Re: Samsung PN43E450 - Won't turn on

Here's a link to a PDF that documents the wiring and pinouts for the E450 and the E490.

[Catman5775]

Re: Samsung PN43E450 - Won't turn on

I am new to this forum, a lot of good info here. I cannot seem to start a new thread due to being new but I would like to add a different problem that maybe I could get some help with, sorry to add this in the middle but I don't know any other way to post. I have a LN40C630K1FXZA that wont turn on, fuses are good, I have 170 volts across yellow capacitors in standby, 400 when on . I only have backlite when cable between main board and power board is disconnected I would appreciate any help Thanks

[Agent24]

Re: Samsung PN43E450 - Won't turn on

I am new to this forum, a lot of good info here. I cannot seem to start a new thread due to being new

https://www.badcaps.net/forum/showthread.php?t=30531 explains it

[spudnik144]

Re: Samsung PN43E450 - Won't turn on

OK, back to our regularly scheduled program

Anyone have any suggestions on my next places to check on the board? Looks like there are debounce capacitors on those pins as Agent24 mentioned. I could try replacing them. I'll post a picture later.

[tom66]

Re: Samsung PN43E450 - Won't turn on

I'd focus on the power supply side - do you get 3.3V back with that board removed? A shorted debounce capacitor would simply cause buttons to stop working... now a shorted decoupling capacitor, on the other hand, could cause all sorts of issues.

[spudnik144]

Re: Samsung PN43E450 - Won't turn on

Yes I do get 3.3 volts with the main board disconnected. But I thought I had eliminated the power supply as the issue with the test I had done earlier.

Here's a picture of the power button connector:

[tom66]

Re: Samsung PN43E450 - Won't turn on

In this case, I mean the main board power supply. The various rails for on board components. The 3.3V to the PSU is just an on/off command and the voltage is usually pulled up by the PSU.