Pn50c490b3d power no video

[crdz66]

HELLO.

I NEED YOU OPINION ON THIS PLASMA TV WITH NO VIDEO.
THE TV LOOKS TURN BUT, THIS IS THE FACTS:
1. I DON'T HAVE LED ACTIVITY ON LOGICAL BOARD.
2. VS_ON SHOW 0 VOLTS.
3. 15V ARE GENERATE LIKE 5VOLTS STANDBY.
4. CAN RUN PROCESS SELF TEST BECAUSE NOTHING SHOW ON SCREEN (PATTERN COLORS PROCESS)

THERE IS A PROCEDURE FOR FIND A SHORT.
When troubleshooting, It's very important to first check Vs, Va, Vsc & Ve
If Vs is missing (0V), disconnect power and check for short. Use ohm meter to measure resistance while disconnecting Y-Board & X-Board supply feeds one at a time.
Turn Power On and Test SMPS with short connector removed for correct Vs voltage verification. (It may only come up briefly but to full level). Again be careful not to reconnect Power Connectors until Vs falls below 10V.

Dump questions.
The leads of the multimeter need to be one vs and the another on ground, right? on power supply?
after that need disconnect x-main board?
what do i expect?

thanks

[ReeceyBurger123]

Re: Pn50c490b3d power no video

So with Ymain and Xmain unplugged Vs comes up and works, with them plugged it it doesn't at all ?

[crdz66]

Re: Pn50c490b3d power no video

let me check

[crdz66]

Re: Pn50c490b3d power no video

well, I unplug the x and y main board and I hear the typical sound from samsung but with no video and vs voltage

[ReeceyBurger123]

Re: Pn50c490b3d power no video

Let me rephrase that, I meant does Vs come up and then shut down with X and y disconnected ?

[crdz66]

Re: Pn50c490b3d power no video

The tv sound remain on with no video at all and vs = 0volts with x and y disconnect

[ReeceyBurger123]

Re: Pn50c490b3d power no video

Ok sounds like the Psu is the problem then if you get 0 volts. Have you checked all the fuses on the Psu ?

[crdz66]

Re: Pn50c490b3d power no video

yes it is ok. anyway check power board out from the tv??

[ReeceyBurger123]

Re: Pn50c490b3d power no video

You can leave it in the tv, just unplug it from the mains. Does your meter have a diode or ohms mode ?

[crdz66]

Re: Pn50c490b3d power no video

yes, it is fluke 116

[ReeceyBurger123]

Re: Pn50c490b3d power no video

Ok put it in to diode mode and check the fuses.

[tw2005]

Re: Pn50c490b3d power no video

When you did the test with x & y disconnected, did you have the probes connected, then power the Tv on watching the meter the whole time? About 200v typically? It will be brief and the only way you'll see it if it's there is if the meter is connected ready to go on powerup and you're watching the instant power is applied.

With this series if either the x or y main are disconnected it goes protect. This is why in the procedure it mentions you may only see it briefly.

If you have Vs briefly then the PSU is most likely ok.


If it is there, this sounds like a typical xmain ( could be ymain failure) . the 42" is certainly prone to xmain failure and also had a firmware upgrade for it.

I expect the 50" model will be very similar in design to the 42 and probably suffers the same failures

[crdz66]

Re: Pn50c490b3d power no video

I test with x and y disconnect and vs doesn't show nothing change.
But you still can hear the samsung sound everytime turn on.
I have 15v present too.
no green light on logical board.

[tw2005]

Re: Pn50c490b3d power no video

It may be the logic board i feel. the logic board is actually like a master controller,, iy's what turns on vs etc and if it detects an issue it goes protect but from the few sammys I've looked at that green activity light should be lit and blink. Normal operation is roughly 1hertz blink, in protect may be once every 3 - 5 secs.
if there is no green LED at all and volatges to it are good, I think it maybe dead.

Cheap part to get and try too. $22

http://www.shopjimmy.com/samsung-bn9...ctrl-board.htm

I don't want to lead you down the wrong path but no green LED sounds wrong..

[tw2005]

Re: Pn50c490b3d power no video

First step in one flow chart i found, No video but sound

check logic board LED operation, if not normal replace logic ctrl board( no green LED is abnormal)

For sure have a dig around the PSU, I don't want to stomp on any other ideas but it may also be worth seeing if you can force it(PSU) on manually and checking if Vs arrives. It gives the forced on test pattern test using the logic board but assuming the logic board is dead you may have to work out whether vs on is a high or low command and apply that at the PSu and see what you get.

I'd do it in isolation of the other boards though and I'm not sure if no load is good or not, common suggestion is 2 incandescant bulbs in series across Vs. I've never done it, just throwing some ideas out there

[tw2005]

Re: Pn50c490b3d power no video

I believe 5V and 12v gets supplied to the logic, I don't know much more at this stage.

[crdz66]

Re: Pn50c490b3d power no video

This morning the vs show voltage (on power supply test points, there are two) and show some kind voltage rise from 3.2 and stop 5.7volts and even the big capacitor show the same 5.7volts. but vs_on never change.
very weird.

[crdz66]

Re: Pn50c490b3d power no video

last update info.
After replace the Power Supply and logic board (y and x board are fine), the tv turn on with vs, vsc, va voltage correctly, but, now the tv is make a weird noise from panel close to power supply. that sound hear like some kind electric plant. constant but no loud.
I check for cracks but can't find nothing. the test patterns doesn't work either. The tv remains on and logic board blink normal 1 by sec.
What else can be???