50PC1d power board

[caspermccormack]

Hi all,

I'am new hear and would like to find out some info on a power board for my 50" plasma LG tv. At first the whole screen went pixelated, random colours on a fuzzy screen with the sound still working. A friend of mine tested the tv and came to the fault being the Y-sus, he also checked the buffers which where fine. When I got the tv back it would switch on but only for 5 seconds and go back into stand by. This he said was caused by the faulty Y-sus and once replaced it would be fine. So after fitting the new Y-sus it still has the same power issue. I have removed the power board and checked for any burn or visual damage on it, all looks fine. There is no way near the volt outputs at the Va or Vs(60v and 192v). There is a tread here that has a simular problem on this board as in the centre blue component is bulgeing at the sides, or maybe the 3 relays at the bottom of the board, this is where i can hear the unit switching off, could these be the cause of this fault?

[TechShui]

Re: 50PC1d power board

The relay you circled in the photo; I don't see it bulging, but there is a black line on it. Is that marker?

The bottom ones look OK.

Are you sure you're not seeing any VA or VS? What screw are you using for grounding?

Try grounding on the metal grommets on the bar that runs across, that's part of the chassis.
Make sure the probe doesn't wiggle or move, tape it down if you have to.

Next, while touching the red probe to the VS wire on the board's plug, use your other hand to turn on the TV.
Just be careful, don't slip, there's a lot of voltage that you're measuring here.

You should get around 189 - 193V, for a second or two and the TV will click, and shut off, and it drops to 0.00.
While you're at it, go ahead and measure ALL the pins coming off the power board.

Yes, there are many, at least 8 or 9 on each connector. Keep a notepad handy to write them down.
It may be easier if someone is helping by turning the TV on and off when necessary.

Always consider the possibility that the new Y-sus replacement is faulty. Where did it come from?
Was it used or "new"? Was it repaired? (i.e. IPM replaced).

A simple test you could perform is unplug BOTH the Y and Z sus boards. Yeah, I know you replied in another thread that unplugging the Z made no difference, what about both? And then try it with the Z plugged in, and the Y unplugged.

[caspermccormack]

Re: 50PC1d power board

The relay you circled in the photo; I don't see it bulging, but there is a black line on it. Is that marker?

Thats marker, only slightly out of shape.

The bottom ones look OK.

Are you sure you're not seeing any VA or VS? What screw are you using for grounding?

Grounding at the metal frame

Try grounding on the metal grommets on the bar that runs across, that's part of the chassis.
Make sure the probe doesn't wiggle or move, tape it down if you have to.

I'm sure it's a good earth

Next, while touching the red probe to the VS wire on the board's plug, use your other hand to turn on the TV.
Just be careful, don't slip, there's a lot of voltage that you're measuring here.

Thats what I was doing, no power when it is turned on.

You should get around 189 - 193V, for a second or two and the TV will click, and shut off, and it drops to 0.00.
While you're at it, go ahead and measure ALL the pins coming off the power board.

Done that, all there, 5v,6v,12v and 19v oh and the 3.4v. Just not getting Va and Vs.

Yes, there are many, at least 8 or 9 on each connector. Keep a notepad handy to write them down.
It may be easier if someone is helping by turning the TV on and off when necessary.

Always consider the possibility that the new Y-sus replacement is faulty. Where did it come from?
Was it used or "new"? Was it repaired? (i.e. IPM replaced).

New board from ebay, I must check who, but had vgood feedback.

A simple test you could perform is unplug BOTH the Y and Z sus boards. Yeah, I know you replied in another thread that unplugging the Z made no difference, what about both? And then try it with the Z plugged in, and the Y unplugged.

Done that too, no joy.

I was chatting to a guy who has fixed one on here, he said he replaced most of the Mosfets on the board and that worked for him. I'll recheck the voltages tomorrow and note them down pin by pin.

thanks for your help,

Casper.

[tom66]

Re: 50PC1d power board

I posted in the other thread you posted in, but here's what I wrote:

Try unplugging the Y-sustain board and seeing if it turns on. Looking from the back of the TV, the board is on the left hand side, and is the largest of the two boards connected to the plasma panel.

In a dark room, does the screen flicker just before turning off? If so you have an AC Detect problem, which I have seen quite a lot with the 42" and 50" PC series plasmas from LG. I'm not sure why, but it's an easy fix (just requires a bit of solder, not even a component to replace.)

I see you've tried the Y-sustain so it's probably the AC Detect problem.

[caspermccormack]

Re: 50PC1d power board

Cheers Tom, will look at it tomorrow and get back to you.

[caspermccormack]

Re: 50PC1d power board

I posted in the other thread you posted in, but here's what I wrote:



I see you've tried the Y-sustain so it's probably the AC Detect problem.

Nothing at all from the screen, red led on the front goes out and then back on after 3 to 5 seconds, back into Standby.

[tom66]

Re: 50PC1d power board

Nothing at all from the screen, red led on the front goes out and then back on after 3 to 5 seconds, back into Standby.

Okay, the screen doesn't always flash when it does this. Is there a pin labelled ACD or AC-DETECT on the power supply outputs (going to the main board)?

[caspermccormack]

Re: 50PC1d power board

Okay, the screen doesn't always flash when it does this. Is there a pin labelled ACD or AC-DETECT on the power supply outputs (going to the main board)?

Yeah its pin1 loc p800 on the powerboard, with the unit switched on it throws out 4.8v before it shuts off again.

[caspermccormack]

Re: 50PC1d power board

So I have checked the following again today and here's the results

vs......anywhere between 70-40v on 3 outputs.
va......1-2v on 2 outputs
5vdc...ok 2 outputs
3.3v....ok 2 outputs
19v.....18.9v 2 outputs
12v.....ok 2 outputs
6v.......5.9v 2 outputs
s-5v.....ok
vs-on....4.7v
5v-d.....4.89v
m5v......4.9v
acd.......4.9v
rl-on......4.8v

There seems to be missing the va and vs on the board. I have a new Y-sus board and it was supplied by GTV in Watford England. I have taken photos of LEDs that light up on the back of the tv, may help diagnose the fault.
The red circle is on in standby, and the 3 green are on when tv is turned on.




Thanks again!!

[tom66]

Re: 50PC1d power board

In standby, is the pin >4V?

When it is turned on using button or remote, does it stay at >4V?

When it clicks off, does it stay >4V?

[caspermccormack]

Re: 50PC1d power board

In standby, is the pin >4V?

When it is turned on using button or remote, does it stay at >4V?

When it clicks off, does it stay >4V?

Standby.......4.89v
Turned on.....4.87v
Off...............4.89v

hope that helps!

[tom66]

Re: 50PC1d power board

Standby.......4.89v
Turned on.....4.87v
Off...............4.89v

hope that helps!

Okay, that confirms it's not an AC detect problem.

It's possibly a power supply problem since you're not seeing enough voltage on Vs or Va. Va is probably the fault.

Can you post a picture of the bottom of your power supply?

If you need them, I've got a spare main board and AV input board for the 42PC1D; I expect they'll be compatible with the 50PC1D. Do your boards have any numbers on them?

[caspermccormack]

Re: 50PC1d power board




There you go!

[tom66]

Re: 50PC1d power board

Bottom side; it's usually green in colour.

Your main board is the one with the HDMI inputs and DTV tuner on it. It does all the processing to display the video on the screen. Are there any model numbers on the main board? (Come to think of it, on mine you had to take the cover off the AV input area to get to the boards, so it might be tricky.)

[caspermccormack]

Re: 50PC1d power board

Sorry mate,



Cheers

[tom66]

Re: 50PC1d power board

Sorry mate,



Cheers

Bottom side of PSU . That's main board, I'll check mine later to see if numbers match.

[caspermccormack]

Re: 50PC1d power board

I'll pull it out and get a snap!! sorry

[caspermccormack]

Re: 50PC1d power board

[ben7]

Re: 50PC1d power board

You say the blue thing in the middle of the PSU is bulging out is sides? That is some type of X-class capacitor I believe.

-Ben

[caspermccormack]

Re: 50PC1d power board

Here you go Ben,