LG Plasma 50PK540 Lightning Victim LED Light Relay Clicks On Plug In Nothing Else

[Michale32086]

LG was the victim of a lightning strike. No bad caps or burn marks, no scorched areas at all..

I get no power on VS or VA.. Zilch.. Nada.. None..

So, I am thinking bad power PCB....

[MagicSmoke]

Re: LG Plasma 50PK540 Lightning Victim LED Light Relay Clicks On Plug In Nothing Else

Unplug power connectors to X & Y boards and see if VS & VA come on and stay on. If not then PSU, if so then X or Y have problems.

[Michale32086]

Re: LG Plasma 50PK540 Lightning Victim LED Light Relay Clicks On Plug In Nothing Else

OK, unplugged the X and Y boards..

The VS acted a little different. It counted up slowly from .000v to around .035v.. But it got no where near the 201v it should be..

I didn't even bother checking the VA, as it's obvious the power PCB is shot...

Thanx for the input.. Still no chance to play with my Rigol!!

[selldoor]

Re: LG Plasma 50PK540 Lightning Victim LED Light Relay Clicks On Plug In Nothing Else

Well it is meter time- Fuses ok?-
Next two gray components between the two relays and the edge of the board.
Think some sort of surge protectors - test them for resistance.
Next Looks like two?? Bridge Rectifiers on the end of the heatsink often suffer in surges

[Michale32086]

Re: LG Plasma 50PK540 Lightning Victim LED Light Relay Clicks On Plug In Nothing Else

And I GOT my meter this time!!

Yea, fuses check out OK..

Next two gray components between the two relays and the edge of the board.

Refering to pic. There?? RED


Next Looks like two?? Bridge Rectifiers on the end of the heatsink often suffer in surges

There?? BLUE

[selldoor]

Re: LG Plasma 50PK540 Lightning Victim LED Light Relay Clicks On Plug In Nothing Else

Yes

[Michale32086]

Re: LG Plasma 50PK540 Lightning Victim LED Light Relay Clicks On Plug In Nothing Else

OK I get about 16ohms +/- .2 or so on the gray components

The bridge rectifiers look in good shape. No burns, bulges or blows... Can I check their voltages??

[selldoor]

Re: LG Plasma 50PK540 Lightning Victim LED Light Relay Clicks On Plug In Nothing Else

If the pins are visible/ touchable from the top of the board set your meter on 600vdc and
test the outer two pins. VERY carefully!!
THEN metre on 600vAC test middle two pins. should be same as mains voltage.
Also test the resistance of the green glass? component near the mains socket.

If the BRs are not easily accessible or you dont want to mess with high voltages
you can do an ohms2000 test on the bridge with power OFF 1 to 2 then rverse the probes and test again then 3 to4 then reverse the probes and just as final test
for a dead short 2 to 3

[Michale32086]

Re: LG Plasma 50PK540 Lightning Victim LED Light Relay Clicks On Plug In Nothing Else

If the pins are visible/ touchable from the top of the board set your meter on 600vdc and
test the outer two pins. VERY carefully!!

That always scares me the crap, as my grandson would say.. But, better to be scared and cautious then brave and stoopid..

The meter I have is auto-adjusting so I don't need to worry about settings beyond the AC/DC setting..

If the BRs are not easily accessible or you dont want to mess with high voltages
you can do an ohms2000 test on the bridge with power OFF 1 to 2 then rverse the probes and test again then 3 to4 then reverse the probes and just as final test
for a dead short 2 to 3

They are fairly accessible, but I'll check the connections this way first...

[Michale32086]

Re: LG Plasma 50PK540 Lightning Victim LED Light Relay Clicks On Plug In Nothing Else

I assume the pins are numbered as shown??

[selldoor]

Re: LG Plasma 50PK540 Lightning Victim LED Light Relay Clicks On Plug In Nothing Else

Yes - we are only doing this as you seemed to suggest there was no power but a short cut and often easier to get at is to test the BIG caps voltage maybe up to 400DC
so again careful does it.

[Michale32086]

Re: LG Plasma 50PK540 Lightning Victim LED Light Relay Clicks On Plug In Nothing Else

The right one...

1-2 6.7 Mohms
3-4 1.69 Mohms

The left one...

1-2 8.7 Mohms
3-4 2.8 Mohms

[Michale32086]

Re: LG Plasma 50PK540 Lightning Victim LED Light Relay Clicks On Plug In Nothing Else

On the marked cap

397V

[selldoor]

Re: LG Plasma 50PK540 Lightning Victim LED Light Relay Clicks On Plug In Nothing Else

Looks good to me so far what is the voltage printed on the cap

[Michale32086]

Re: LG Plasma 50PK540 Lightning Victim LED Light Relay Clicks On Plug In Nothing Else

450v

[vinceroger69]

Re: LG Plasma 50PK540 Lightning Victim LED Light Relay Clicks On Plug In Nothing Else

On the power board there are about 7 white ceramic resistors (2 on the left 5 on the right of the psu) do these all test ok? it should say on the side of them what they should read.

[selldoor]

Re: LG Plasma 50PK540 Lightning Victim LED Light Relay Clicks On Plug In Nothing Else

Just in case you were wondering or anyone spots it the test for the bridge was not quite correct - It was ok for testing for a short but to test correctly meter should be in Diode mode - hence the reason for reversing the leads should show something one way and infinity when the leads swapped.

[Michale32086]

Re: LG Plasma 50PK540 Lightning Victim LED Light Relay Clicks On Plug In Nothing Else

On the power board there are about 7 white ceramic resistors (2 on the left 5 on the right of the psu) do these all test ok? it should say on the side of them what they should read.

Should those be tested with the unit powered up??

[Michale32086]

Re: LG Plasma 50PK540 Lightning Victim LED Light Relay Clicks On Plug In Nothing Else

Just in case you were wondering or anyone spots it the test for the bridge was not quite correct - It was ok for testing for a short but to test correctly meter should be in Diode mode - hence the reason for reversing the leads should show something one way and infinity when the leads swapped.

Ahhhhhh Makes sense.. Sorta

[vinceroger69]

Re: LG Plasma 50PK540 Lightning Victim LED Light Relay Clicks On Plug In Nothing Else

With power off and on ohms mode on meter.