LG 42pq3000 just backlight

[steve2k34]

Hi can anyone help me at all ive got a lg 42pq3000 plasma tv here when i switch it on i get no picture its just glowing as you can see in the picture i get like a snowy sound like a hissing i no its sound as if i press mute it dissapears please can anyone help me diagnose this problem at all many thanks

[tom66]

Re: LG 42pq3000 just backlight

OK, this is a plasma. It does not use a backlight. Each cell emits its own light. But that means the panel, sustain boards and power supply are probably working. Probably.

Let's rule out the plasma panel, sustain boards and the power supply: Do you see the points marked "EXT_AUTO_GEN" on the control board?

• Turn TV off.
  
• Disconnect LVDS cable from control board (this is the top most black tape connector in this picture: https://www.badcaps.net/forum/attach...2&d=1359559144.)
  
• Take a 100 ohm resistor and jumper between the auto gen holes.
  
• Turn TV on.
  
• The panel should show test patterns - does it?

[tom66]

Re: LG 42pq3000 just backlight

Oh and service manual if you need it
http://www.tgohome.com/ServiceManual...&Search=Submit

[steve2k34]

Re: LG 42pq3000 just backlight

i dont have an resistors to test that so looks like im srtuck for the moment

[tom66]

Re: LG 42pq3000 just backlight

Maplin Electronics sell resistors.
Or you can jumper across it with a wire, but I do not want you to damage the board in case this is not OK.

[steve2k34]

Re: LG 42pq3000 just backlight

right i will have to pop to maplins in the morn which holes exactly do i need to stick this resistor into

[tom66]

Re: LG 42pq3000 just backlight

Here

[steve2k34]

Re: LG 42pq3000 just backlight

right thank you, just making sure as dont want to mess it up further. Thanks for your help much apreciated, i will look into this further tomorrow.

[steve2k34]

Re: LG 42pq3000 just backlight

ive put the 100 ohm resitor in and i get all the test patterns show up now

[tom66]

Re: LG 42pq3000 just backlight

Great, in which case, replace the main board (unless you want to repair it.)

[steve2k34]

Re: LG 42pq3000 just backlight

the main board with the hdmi sockets etc?

is there any chance you would no how to repair the main board, as whats there to loose apart from having to buy a new one many thanks

[tom66]

Re: LG 42pq3000 just backlight

Yeah, that's the main board.

See Retiredcaps thread on testing voltage regulators:

https://www.badcaps.net/forum/showthread.php?p=300999

BTW, I notice a 50" main board on eBay. That probably won't work as the 50" panel is 1366x768 and the 42" is 1024x768, but it might be possible to change the settings in firmware.

[steve2k34]

Re: LG 42pq3000 just backlight

Thank gonna have to buy me self a multimeter looks quite hard to do but will have a go at it

[tom66]

Re: LG 42pq3000 just backlight

Maplin Electronics sell multimeters for £5 each. Or eBay.

[steve2k34]

Re: LG 42pq3000 just backlight

yes ive been lloking around for one and seen there about £5.00 is there a certain one you would sugest to me on ebay? and also when i find what regulator is wrongt are they easy to source as sometimes maplin dont stock stuff

[tom66]

Re: LG 42pq3000 just backlight

You can order the regulators on eBay or Farnell.

Maplin's basic meter is fine.
http://www.maplin.co.uk/domestic-multimeter-37279

The DT830B is also a good meter for basic usage, and it's probably made by the same company as the Maplin meter.

[steve2k34]

Re: LG 42pq3000 just backlight

got my multi meter

this may sound like a daft question but im just being cautious do i have the board fully connected up to the tv ?

do i have the tv plugged in if so in standby or switched on for my readings?

[tom66]

Re: LG 42pq3000 just backlight

Yes, you need to have it powered on, with the fault showing on the display.

[steve2k34]

Re: LG 42pq3000 just backlight

right if ive done this right here is my readings im trying to do them of the data sheet but a bit confused with it at the mo

ic1107
az1085s
adje1
832j73

1- 0.60
2- 1.85
3- 4.85



ic1102
az1085s
adje1
832j73

1- 0.03
2- 1.28
3- 3.29

ic1104
az117d
1.8e1
838j25

1- 0
2- 1.81
3- 3.3

ic1103
az117d
-3.3e1
853k18

1- 0
2- 3.3
3- 5.05

ic1106
az1085s
-3.3e1
903j80

1- 0
2- 3.3
3- 4.84

[selldoor]

Re: LG 42pq3000 just backlight

Those results are spot on.