LG 42PA4500, Stand by only.

[Shinju]

Hey all,

I got this little 42" LG plasma the other day and it seems to be stuck in stand by only.

The first strange occurrence is when first plugged in there is no stand by light on the front of the panel. The mainboard has a red LED blinking on and off every few seconds, when I unplug it and plug it back in the front standby LED comes on and the mainboard LED stops blinking.

Kind of like this guys issue here.

https://www.badcaps.net/forum/showthread.php?t=43543

I have broke down the panel to try and get voltages but all I could get was 5.2v standby, my probes are too large for the super small plugs this panel uses.

I tried taking out the Y and Z boards to see if i could get the SMPS to fire but no luck. It also seems the SMPS power the X and the Y piggy backs off the X.

I cannot seem to find a troubleshooting flowchart for this panel to see if there is a way to fire the SMPS to verify the Main/SMPS is good.

Also this panel has a Panasonic IC driven Y drive.

I am using the photo from the thread above as out TV's are damn near Identical just his mainboard has a TV card slot and mine doesn't but the flow if the panel is the same.


Oh and I should mention, when trying to power the unit on via the powrer butting the red LED on the front of the panel just blinks one time and goes back to standby.
thanks!

[tom66]

Re: LG 42PA4500, Stand by only.

You should try jumpering the PSON and VSON to enable the PSU - it sounds like a main board issue to me

[Shinju]

Re: LG 42PA4500, Stand by only.

You should try jumpering the PSON and VSON to enable the PSU - it sounds like a main board issue to me

I can just use a jumper wire no need for a resistor to do that correct? with the mainboard harness disconnected.

[Shinju]

Re: LG 42PA4500, Stand by only.

This is what I see on the power supply legend for the main board harness.

[tom66]

Re: LG 42PA4500, Stand by only.

Resistor for both, I would recommend.
But IIRC if you ground AUTO GND it should work, thats a self test mode.
Main board must be disconnected for this to work

[Shinju]

Re: LG 42PA4500, Stand by only.

So I tried the grounding of the Auto GND with the mainboard and LVDS disconnected and nothing happens.

I also found a resistor (may or may not be correct resistance) and jumped PL_on and AC_on with mainboard/LVDS and AUTO_gen jumped on the logic board (nothing happens) I tried having the LVDS and no AUTO_GEN jumper (nothing happens) I tried with the sustain boards unplugged From the SMPS (nothing happens).

I did get a replacement main and the standby light comes on every time when I plug in the unit un like the original mainboard issue above, I tried to power on the unit it blinks once and goes right back to solid red. The LED500 LED flashes red for a second when trying to power on the unit.


I have also tried swapping the sustain boards out and combo with old and replacement boards and still no SMPS power up.

I think the SMPS is toast, would that be a safe bet?

[Shinju]

Re: LG 42PA4500, Stand by only.

/bump

[tom66]

Re: LG 42PA4500, Stand by only.

Can you use 100 ohm resistors for jumpering? You could test your unknown resistors with your multimeter. Also the smps must be disconnected from the main board when jumpering

[Shinju]

Re: LG 42PA4500, Stand by only.

Can you use 100 ohm resistors for jumpering? You could test your unknown resistors with your multimeter. Also the smps must be disconnected from the main board when jumpering

I can look at the resistor when I get home, but yes the mainboard was completely unattached from the power supply and logic board.

I think the resistor was 20ohm I took it off a blown Zsus from my 60PV450 repair.

With grounding Auto_GND I grounded it off one of the grounding screws holding the SMPS to the chassis and I also tried another ground point, no luck.

I will see if I cannot find a 100ohm resistor.

[Shinju]

Re: LG 42PA4500, Stand by only.

Got a used (but tested) SMPS coming today, going to give that a shot when I get home this evening.

[Shinju]

Re: LG 42PA4500, Stand by only.

Bad SMPS and Bad Mainboard.

It's alive!

[Shinju]

Re: LG 42PA4500, Stand by only.

Update.

So the panel was working fine after the new SMPS, I let my test video run for 6 hours and called it good, unplugged it and put it away.

Fast Forward to today, I plugged it in and turned it on, the screen primed like normal and the second the mainboard kicked on the no signal graphic pops up and at the middle bottom of the screen about 4" ish long and about 2" high there was a small red pixel storm that lasted about 3-4 seconds ish and it disappeared.

Va voltage spec was 205, SMPS was 204 I bumped it up to 205.5, all other voltages are spot on spec.

Is the ysus failing, or should I put the SMPS voltage back to where it was?

Also noticed on power up with the red pixel discharge there was some pretty good image retention going on from going in and out of menu pages, seems to go away after a few minutes or more.

[Shinju]

Re: LG 42PA4500, Stand by only.

Update

Seems the red pixel storm only happens on cold start, no red pixel misfire at all in the blacks at all outside of the cold start.

[tom66]

Re: LG 42PA4500, Stand by only.

I've seen that one some panels. My tweaked Kuro has horrible sparkles for the first 10 seconds if it's been off for a while. But they go away after that.

Curious what the pic quality is like on one of the budget 42" panels. I saw an LG 42PN430 in an Ikea as a demonstrator. It looked *terrible*. Absolutely one of the worst images I've seen from a plasma or LCD TV.

[Shinju]

Re: LG 42PA4500, Stand by only.

Tom66

The picture is surprisingly decent, it does get a little screen doorish if you are close to it like the 43" Samsung 720p budget plasma panels.

It's no Panasonic, pioneer on the black levels but it does ok.

So the red sparkles are normal? I do have another ysus I can try.

[satveer1984]

Re: LG 42PA4500, Stand by only.

Hi Tom66,

I am having LG 42' Plasma Tv with model no.LGPN4500. One day i am watching the movie then some blast sound comes from my tv and it get off. Then i open its back cover to check fuses but fuses is ok.

I have done some study on it mention below:

1. I have check power supply voltages VA & VS as mention in grid (+5, VS-205, VA-55) Exact output value shown in multimeter--when tv in not on

2. When i turn on the Tv VA & VS value get changed to +5 to 0, VS-205 to 80 and decreasing, VA-55 to 19 and decreasing.

3. I fix Z sus board by replacing faulty NPN : RJP30H2A and it work perfectly.

4. I have check Y buffer board, there is no shortage on it. but when i join Y sus board to Z sus board, Z sus board got blast again.

5. I tried with short EXT_AUTO_GEN but get any screen or sound.

6. There is no shortage or fault detect in Ysus board.

Please help me.

[satveer1984]

Re: LG 42PA4500, Stand by only.

Pics attach for reference if required clear and closed pic please confirm

[satveer1984]

Re: LG 42PA4500, Stand by only.

It got short need to replate it??

[satveer1984]

Re: LG 42PA4500, Stand by only.

tom please help

[katiti]

Re: LG 42PA4500, Stand by only.

i have an lg 42sc410 model which just went into standby. the power supply seems ok. sometimes it powers on for 30 minutes and goes back to standby. where should i start. all the voltages are ok on the smps. please help