50PB560B -LG common problems?

[Unspun01]

Re: 50PB560B -LG common problems?

Yes, connecting the copper rings of the holes. Paperclip will apply gentle spring pressure to hold in place. Don't insert too deep - you don't want to accidentally contact other ground points.

Lift black plastic from circuit board side I thing. Look closely at it. You should see a hinge appearance and it should be obvious how it opens.

[jp_fizzer]

Re: 50PB560B -LG common problems?

Ok, so I am trying to connect the two holes, basically I want to connect the copper rings around the holes to each other?

For the black connector, am I slipping my fingernail under the ribbon edge (right side) and lifting, or the circuit board (left) side?

[Unspun01]

Re: 50PB560B -LG common problems?

I really only see two small next to R451 and R452 and below it is a pad labelled Auto.

I am actually not really sure how to release that ribbon connector that goes to the main board. I assume I lift a clasp and then the ribbon cable will pull out but I cannot figure out what I am supposed to lift. I tried both the black plastic part and the silver metal part and neither want to lift easily.

Yes the two pins labelled AUTO are the ones you need. Jumpering these pins with mainboard disconnected and plugging in the tv should let the tv turn on and display test patterns if panel and panel boards are working. It helps you isolate mainboard issues.

Gently lift the black plastic part with fingernail and gently remove ribbon cable by pulling to the right. Very little force is required. If you need force you are doing something wrong and should re-evaluate before breaking something.

[Unspun01]

Re: 50PB560B -LG common problems?

So I unplugged all the boards again and plugged them back in. There was a huge spark when I plugged in the P811 connector but when I turned the TV back on this time it came back on. I have checked all the voltages with the TV on and they are all the same except that pin#6 on P811 is now at 55V where as it was 0V when the TV was plugged in but not working. Is this the key? Does anybody know what that might mean?

The huge spark is a result of plugging in the cable when capacitors were not completely discharged. Possibly the VA supply (approx 60V) or the VS supply (approx 210V). Try to avoid doing this as it can scare you and it is damaging to your TV. You can use a 1W-5W ceramic 1kohm resistor to safely discharge power supply voltages (VA-gnd or VS-gnd)

[jp_fizzer]

Re: 50PB560B -LG common problems?

Attached are photos of the back of the TV and a closeup of the Logic Board.

I really only see two small next to R451 and R452 and below it is a pad labelled Auto.

I am actually not really sure how to release that ribbon connector that goes to the main board. I assume I lift a clasp and then the ribbon cable will pull out but I cannot figure out what I am supposed to lift. I tried both the black plastic part and the silver metal part and neither want to lift easily. I figured I better ask before I break something.

[dick_barton]

Re: 50PB560B -LG common problems?

There was a huge spark when I plugged in the P811 connector but when I turned the TV back on this time it came back on.

In addition I would also check the pins on P801 plug and connector for any damage due to sparking.

[Unspun01]

Re: 50PB560B -LG common problems?

...did some more trouble shooting with the schematics in hand and found that the mosfet was not turning on or off . The mosfet supplies 5v from the 5v-stb which goes on to provide 3.3v 1.8v 1.15 volt.This is the mosfet I jumpered which seems to have restored most of the functionality.The mosfet is Q604 and is switched by Q603 an NPN transistor.Jumpering the Drain AND Source of Q604 is what gave the set functionality again..

Helikvar:

Thanks for posting this information.

I can confirm that your information is good.

I have also repaired a 60PB5600 plasma mainboard similar to 50PB560B in this same manner. For anyone who is interested, here is a summary of the symptoms with my TV and the fix:

Bad mainboard. Initial issue: Has power, will respond to power button and turn on, but no image or menu. Can't turn off once turned on.

Replaced broken HDMI port, replaced MMBT3906 PNP transistor (Q203?), replaced 10k smt resistor.

Was still dead - No power. Replaced -30V, -4.3A SOT23 P-channel FET AO3407A (Q604) (LG part EBK60752501), and now TV turns on.

I got the transistor from an old scrap 37LD450 mainboard (Q409).

Hope this helps someone.

[jp_fizzer]

Re: 50PB560B -LG common problems?

Oh wow, I am really glad I did not bake the boards.

So I see now why the 55V is correct on pin#6 of P811. That pin corresponds to VA which is supposed to be 55V.

Attached are photos of P811 and P813 (which is just the other end of P600 so they are exactly the same) and also a photo showing what the VS and VA voltages are supposed to be.

So the fact that when the TV is working properly pin#6 on P811 is the correct 55V but when the TV is not working properly it is 0V, does this tell me anything useful?

[Unspun01]

Re: 50PB560B -LG common problems?

This is a plasma TV model. It has a logic board located directly in center of TV below the power board. It has a built-in self test feature that can test the panel and panel driving boards without a mainboard connected.


1) UNPLUG THE TV.

2) Disconnect the cable between the mainboard (the one with AV inputs) and the logic board. It shouldn't matter which end of the cable you unplug.

3) On the logic board there are 2 open-holes that can have a small jumper inserted ( like a small paperclip). The two points have a label printed on the board called AUTO_EXT_GEN or similar. Spend a few minutes looking for it - you'll find it.

4) Insert a bent paperclip into both holes of the AUTO_EXT_GEN holes with mainboard disconnected and plug in the tv.

5) If power board and other panel boards are ok you should see test patterns display on your panel automatically.

Make sure that you do not insert the paperclip or jumper wire too far. You do NOT want the ends of the paperclip or wire to contact the logic board and the metal underneath that is the back of the panel (it is grounded).

[dick_barton]

Re: 50PB560B -LG common problems?

Can you post pictures of what you are refering to. The 55V is your VA supply. I would be looking at the solder joints on the Zsus board and ensure that they are all good.
What is the part number written on IC704???

Remember that we don't have the set in front of us and probably have never worked on this model before.

Edit
IC704 is the XD engine on the Logic Board and will run hot.

[jp_fizzer]

Re: 50PB560B -LG common problems?

Ok, so I did some more research on the subject and decided not to bother baking the boards yet. I put everything back together and the TV turned on. I cycled the power and it would not come back. So I unplugged all the boards again and plugged them back in. There was a huge spark when I plugged in the P811 connector but when I turned the TV back on this time it came back on. I have checked all the voltages with the TV on and they are all the same except that pin#6 on P811 is now at 55V where as it was 0V when the TV was plugged in but not working. Is this the key? Does anybody know what that might mean?

Also, there is a small board below the power board that has 4 ribbon cables coming into it. It has IC704 on it which is very hot to touch. Also, D401 on that same board is now flashing, it was not on when the TV was not working.

Any suggestions would be greatly appreciated.

[dick_barton]

Re: 50PB560B -LG common problems?

You don't say what the various pinouts for P600 ans P811 are?? They should all have names alongside them as shown on the circuit board.

There should be a white label on the back of the plasma screen giving the various voltages that should be present. It looks like you're missing VA to start with but that could be for other reasons.
Can you post a picture of the label as well as the boards and one showing alll the boards connected to each other.

[Unspun01]

Re: 50PB560B -LG common problems?

DO NOT place the power board in the oven. Ever. You will create irreversible damage. This is not a fix for power board on this TV or ANY TV.

NO NO NO.

Also, DO NOT put this mainboard in the oven. This model of tv does not have BGA main IC processor chip so this is not going to fix either and may cause irreversible damage to your board.

Let me be clear, some people have had luck with TEMPORARILY repairing certain models of LG plasma, LED and LCD tvs that have BGA main processor IC under a heat sink that was known to warp the circuit boards over time.

This is not the same type of mainboard . OVEN IS NOT A FIX.

[jp_fizzer]

Re: 50PB560B -LG common problems?

So I have tried disconnecting all of the various boards one at a time and powering it up but never any difference so I have no idea which board might be the problem. I have read about some people having success reflowing the boards in their oven. As a last ditch attempt to revive the TV is there any point in putting the power board and main board in the oven?

[jp_fizzer]

Re: 50PB560B -LG common problems?

Hello, I have a 50PB560B and I started having an issue where I would have to try turning the TV on and off several times before it would finally turn on. The standby light would always go on and off, but the screen would just stay black. Now, I cannot get the screen to ever come on, although the standby light still switches when I turn the power on and off. I have thoroughly checked all the boards and cannot find any suspect looking components, no bulging, no leaking, no charring.

I have checked the voltages on the P600 connector on the main board as well as P811 on the power board. I think they look okay compared to the diagrams printed on the boards, here are the voltages:

P600:
pin 1: 17.3V
pin 3: 0
pin 5: 5.2V
pin 7: 5.2V
pin 9: 0
pin 11: 0
pin 13: 5.2V
pin 15: 1.5V
pin 17: 3.2V

P811:
pin 1: 201V
pin 2: 201V
pin 3: blank
pin 4: 0
pin 5: 0
pin 6: 0
pin 7: 5.2V

I really have very little experience but would love any help anybody is willing to give. Does anybody have any suggestions for what I can check next?

thank you very much.

[Helikvar]

Re: 50PB560B -LG common problems?

Hello everyone. My second post though I have been following this group for a year or more.I too have a 50PB560B that was completely dead when brought to me.The HDMI port had been completely torn out from the main board along with several resistors and a few transistors.Some tracks in the board were damaged as well.Searching the internet found nothing for a main board .Out of stock was all I found.But thanks to the schematics in this thread I was able to replace all of the missing components. Still need to fix a few traces but by jumping a mosfet on the main board I have gone from a completely dead set to turning it on and off and displaying the menu and all its functions.I even have the led lit up now while off. I had to order the p-ch mosfet that I jumpered and should have it in a week or so.I should know then if that is the issue with it.I was going to buy the repair kit from jimmys but did some more trouble shooting with the schematics in hand and found that the mosfet was not turning on or off . The mosfet supplies 5v from the 5v-stb which goes on to provide 3.3v 1.8v 1.15 volt.This is the mosfet I jumpered which seems to have restored most of the functionality.The mosfet is Q604 and is switched by Q603 an NPN transistor.Jumpering the Drain AND Source of Q604 is what gave the set functionality again.I will update this post once the new mosfets arrive and are installed.

[Unspun01]

Re: 50PB560B -LG common problems?

Tried the repair kit. No dice.

replaced all three IC's in the repair kit. cant even get an error code of any sort unless there is no power to the main.

when its all plugged up it does nothing when you hit the power button. That repair kit had a new eeprom, a chip for what i think is audio, And the new main IC.

the ic doesnt get hot or anything.

The repair kit should have solved your problem. The mainboard is your problem - especially since every other board appears normal and you see a test pattern screen with mainboard disconnected.

The repair kit has 3 ICs: Main IC (IC400), Audio IC (IC606) and SPIFLASH/EEPROM (IC505).

In all likelihood, only Main IC400 is bad, but you cannot get the part separately anywhere else so you have to buy the 3 part kit. The other 2 ICs (audio IC and EEPROM) could have been kept aside for now.

Audio IC (IC606):
If bad, Audio IC could pull down voltages and prevent main IC from getting correct voltages, and perhaps no standby LED. If bad, IC would likely get hot but I think you checked this. If bad, TV may not start, but even if audio IC is completely removed TV should start (no sound) if all else is good. Audio IC is not usually the problem and didn't need to be replaced.

SPIFLASH/EEPROM (IC505):
If bad, would usually prevent the TV from booting correctly, but you should still see standby LED on front of TV. SPIFLASH/EEPROM likely not your issue and didn't need to be replaced.

Main IC (IC400):
Totally dead TV as you describe still points to the main IC LGE8220. There could be a few things at work here:

1) Is the IC installed in correct orientation? It is possible to install 180 degrees out of place.

2) This IC is not easy to work with due to fine pitch between pins. Check under strong magnifying lens (or with multimeter) to ensure no shorts between adjacent pins which should not be connected.

3) You may not have solder bridging adjacent pins, but with 156 pins, it's possible some aren't soldered at all.

I do not know if you used hot air rework station, or infrared solder station, or manually soldered each and every pin. You didn't say.

With hot air or infrared - if you did not adequately heat the area, you may have some pins making good connection, and some pins making no connection. You may need to re-touch some with fine-tip solder iron.

I strongly advise you to RE-EXAMINE all of your solder connections under good light with strong magnifying lens to ensure you do not have any solder bridged between adjacent pins, that the IC sits completely flat against the board and that every single pin is actually soldered.

Can you please upload high resolution close-up photos of your solder work on the main IC and audio IC under good light from a few different angles?

[Bloopeta]

Re: 50PB560B -LG common problems?

Did you ever get anywhere with this?? I have the same problem

[budm]

Re: 50PB560B -LG common problems?

Ahh gotcha. Im not super familiar with those but its good to know what i need.

What im curious is, Would it be an issue for the main chip to be expecting 3.3v and gettin 3.194v that was one possible issue with the voltage. the other was 1.15 getting 1.17v which i figured was pretty close on that one.

Look up the spec sheet to if it is out off spec or not.

[Demonata08]

Re: 50PB560B -LG common problems?

It looks like you need an oscilloscope for those last three tests.

Ahh gotcha. Im not super familiar with those but its good to know what i need.

What im curious is, Would it be an issue for the main chip to be expecting 3.3v and gettin 3.194v that was one possible issue with the voltage. the other was 1.15 getting 1.17v which i figured was pretty close on that one.