lg 60pz550 black screen, no power, etc

[legonch]

Ive got a lg 60pz550 tv, it had the purple bars across the top and bottom. I read on here how to fix that, and re soldered all the connections.

When I put everything back together, I do not get the screen. Nothing. I hear the relays click.

I have used an ohm meter to check all the fuses i can see on each of the boards, and they test out all about 1.6.

I have the green led light flashing a pattern. i do have 120 volts going into the main board.

I have tested the power going out to the ysus and vsus boards. One time, I did have power at the plug to the ysus board, but I can not duplicate that at this time. None of the connectors for the boards have any voltage detectable.

I pulled the flat cable out of the av board, used a wire to jump in the holes, and screen will not display anything.

Im suspicious of the main board, but confused why one time I did have voltage at the ysus connector.

At this point I need some help. Im pretty tech savvy, can solder, etc. Thank you in advance.

[tvtimmy]

Re: lg 60pz550 black screen, no power, etc

You will have to post clear pictures of the boards and the whole back of the set.

[legonch]

Re: lg 60pz550 black screen, no power, etc

Here are the pictures as requested. Thank you for helping me

[tvtimmy]

Re: lg 60pz550 black screen, no power, etc

What did you re-solder? Just the coils on the y and z sus boards? There could be bad joints on the power supply. Check them out.

[legonch]

Re: lg 60pz550 black screen, no power, etc

I did just resolder the connections on the two boards. Tv powered up fine before i did that though. Dont see anything that i did that would cause the tv not to power up.

i used an ohm meter on all the fuses. they all check out. I dont think i need to remove the fuses from the board to check them do i? They are soldered in type.

[tvtimmy]

Re: lg 60pz550 black screen, no power, etc

So to be clear , you only fixed the joints on these parts circled in red?

[tvtimmy]

Re: lg 60pz550 black screen, no power, etc

Pic #1

[tvtimmy]

Re: lg 60pz550 black screen, no power, etc

Pic#2

[legonch]

Re: lg 60pz550 black screen, no power, etc

yes, thats all i touched. just disconnected the boards, resoldered the connections, and put back together. Nothing else

[legonch]

Re: lg 60pz550 black screen, no power, etc

I did some multi meter tests, pic shows where I have voltage and where I dont. One relay clicks when I plug it into the wall.

I have a long long short short pattern on the led light on the smaller board

I can not get tv to power on with the remote or by touching the button in front, this used to work before the solder as well.

[tvtimmy]

Re: lg 60pz550 black screen, no power, etc

Here is a list of parts from a repair kit. Start with checking the 5v standby pin and then check the parts on the list.

[legonch]

Re: lg 60pz550 black screen, no power, etc

Here is a list of parts from a repair kit. Start with checking the 5v standby pin and then check the parts on the list.

Im not sure where the standby pin is located. That the 5v labeled on the ysus and zsus boards?

[tvtimmy]

Re: lg 60pz550 black screen, no power, etc

Stb or 5v should be on this connector.

[legonch]

Re: lg 60pz550 black screen, no power, etc

Okay, got a new multi meter. Attached is the pictures of each board with the noted voltages. I do have 5 volts on both the sus boards. on the left board, on the left lower side, the place to test voltage, i get 0 volts then 5 volts, and repeats.

Any ideas?

[tvtimmy]

Re: lg 60pz550 black screen, no power, etc

Watch this video. It should help you check everything.
https://youtu.be/aZF57Bok7Ws

[legonch]

Re: lg 60pz550 black screen, no power, etc

found some of the mosfets are grounded.

the second heat sink up from the bottom on the left board gets smoking hot, the rest do not. That mean anything?

Ive got the correct voltages going to each sus board.

[legonch]

Re: lg 60pz550 black screen, no power, etc

found some of the mosfets are grounded.

the second heat sink up from the bottom on the left board gets smoking hot, the rest do not. That mean anything?

Ive got the correct voltages going to each sus board.

[tvtimmy]

Re: lg 60pz550 black screen, no power, etc

Which boards have the shorted fets? Do they have a Q for the position eg. Q421,Q602?

[Tvbob]

Re: lg 60pz550 black screen, no power, etc

DO your self a favor.... Change the Sustain board with the shorted fet.s and check your buffer boards for shorts (there are youtube videos)
You are not going to be able to check the gate drive components on you bad board and new fet's will POP. Ebay is a good source for used boards

[Unspun01]

Re: lg 60pz550 black screen, no power, etc

DO your self a favor.... Change the Sustain board with the shorted fet.s and check your buffer boards for shorts (there are youtube videos)
You are not going to be able to check the gate drive components on you bad board and new fet's will POP. Ebay is a good source for used boards

Should not need to replace the board. YSUS and ZSUS are easy repairs for this TV with ZSUS being more common failure mode.

The heatsinks are too small for this TV and the 4633 IGBTs commonly run hot and short circuit leading to the failure. (Fairchild FGPF4633 330V PDP Trench IGBT). The gate driver ICs (Fairchild FAN7371) are usually ok, but can also fail sometimes. Any I've had to replace were shorted and easy to find. If you don't know how to check, you are better to replace all the bad IGBTs and their associated drivers with a kit from ShopJimmy:

https://www.shopjimmy.com/lg-ebr7356...repair-kit.htm

On my previous repairs, all of the other small surface mount resistors and components were ok and I didn't replace, but the fuse, the IGBTs and their drivers should definitely be checked.