lg 60ld550

[tearale]

Have a lg TV 60ld550 that won't power up. Red light blinks, but no picture or sound. Tried replacing power board, same results. I at least believe the power supply is good. Need further advice

[mmartell]

Re: lg 60ld550

Start with pics of the internals, one wide shot and one of each board.

[charis]

Re: lg 60ld550

If your led blinks and the tv dont start is inverter problem.See if you have start signal from main board.
Check if you have 3.2v on DRV_ON and also PWM-DIM1 tupical 1.2 -1.6v.
Also check my post about lg Start Up Sequence and Voltages.

https://www.badcaps.net/forum/showthread.php?t=53414

[dick_barton]

Re: lg 60ld550

Hello Charis,
It's a good instruction guide but a bit confusing where you say

To test Tcon jump 12v from SMPS to the Tcon fuse.
Disconect the LVDS cables Jump VCC 3.3v to the LVDS(CN1) connector ground pin.

Edit
So the Tcon is powered at the fuse by +12V and the TCON ground is connected to +3.3V

[charis]

Re: lg 60ld550

Correct.
Jump 3.3V from
the VCC (is label on pcb) to
pin of CN1 who is ground.
Jump 12v from power to the t con fuse F1 .

[BCM_OC]

Re: lg 60ld550

Long time listener, first time caller.

Was going to start a new thread, (and will if that's what the Mod's want me to do) but I seem to be having the same problem with the same LG model 60LD550 TV, so I thought this might be the best place for it. Hopefully you guys can help me out.



So, here's the story - This TV went out on the previous owner, and they attempted their own repairs before finally giving up. Previous owner stated that they replaced the main board, but that didn't fix it. I first thought that this meant that they bought a new or reconditioned board, but upon further questioning it became a little *fuzzy*.

When I asked about the "new" board and asked if they still had it, the owner stated they they were trying to get a refund for it. It was not clear if he still had it in his possession, and they were not forthcoming with any more info. According to them, the TV did nothing (black screen) with the original board and had a "blue screen" (only) with the repaired board.

When I got it back to my shop and tested it, I initially had nothing at all. No picture, no sound, no LED's. I opened it up and I found bent pins on one of the mainboard connectors, two ribbon cables not in their (closed) connectors, and a plug-in connector that looks like it was assaulted with a pair of needlenose pliers.

After fixing the bent pins, properly connecting the ribbon cables, and checking and re-seating the molested connector, I tested it out. The power supply turns on and off, but seems to have a high pitched whine. Front panel LED now comes on steady with the power connected, but flashes once the TV is turned on. Power supply seems to test out OK. 12v rail is a little low at 11.7, but I'm thinking that's still probably "OK". Saw the tips about the inverter (above posts) and tested that, but get nothing at the "INV On" pins.

Next, I followed the (attached) diagrams and pulled the board for closer inspection. Found what I think might be an issue at IC 8100. Pins 1,2, and 3 are bridged with solder. In the diagram it looks as though pins 1, 2, and 4 are the pins that are supposed to be bridged. Also, looks to me like maybe this was a repair, but I'm not certain of that.

Anyway, I'm turning to the experts at this point. So,what do you think? Where should I go from here with this?

Thank you for any help.


(BTW, sorry for the long post, but I thought it was necessary to fully understand the situation)

[nomoresonys]

Re: lg 60ld550

While testing inverter on pin, test with tv plugged in and off which is standby, then hit power see if meter reading changes, inverter on signal should be coming from mainboard. Sounds like the previous owner had not a clue what to do, if you get a good mainboard, might solve issue.

[BCM_OC]

Re: lg 60ld550

While testing inverter on pin, test with tv plugged in and off which is standby, then hit power see if meter reading changes, inverter on signal should be coming from mainboard. Sounds like the previous owner had not a clue what to do, if you get a good mainboard, might solve issue.

Thank you.

When I test as you asked, I get a little over 4 volts on that terminal (18) on power up, but then it drops off rapidly to just over zero.

Here's a schematic for the power supply and the P8000 connector on the main board, and pictures of each. The harness connects these two connectors pin to pin.

[dick_barton]

Re: lg 60ld550

Your photo of the EEPROM shows it as a 24C16WP and attached is a snippet from the data sheet for that IC.
However it does not appear to match the layout shown in your photo. Data sheet says pin 3 is not connected (NC). Your schematic shows it is connected to a resistor?

I think there's definitely an error in the schematic and the IC cannot be an 24C16 as stated in the diagram. Pin 3 is connected as you can see in the photo of the IC.

Edit
You mention you have the 12V but do you also have the 24V supply?

[nomoresonys]

Re: lg 60ld550

.

[nomoresonys]

Re: lg 60ld550

Thank you.

When I test as you asked, I get a little over 4 volts on that terminal (18) on power up, but then it drops off rapidly to just over zero.

Here's a schematic for the power supply and the P8000 connector on the main board, and pictures of each. The harness connects these two connectors pin to pin.

Ok, that looks like what you should expect on that pin.

[BCM_OC]

Re: lg 60ld550

Your photo of the EEPROM shows it as a 24C16WP and attached is a snippet from the data sheet for that IC.
However it does not appear to match the layout shown in your photo. Data sheet says pin 3 is not connected. Your schematic shows it is connected to a resistor?
I think pin 3 (NC) and pin7 (WC) have been swapped in the diagram in error.

Good catch. After posting the pics and schematics earlier, I just kept looking at the board and the schematic. I ended up taking that solder bridge off - as it didn't seem necessary for legs 1 and 2 (already going to ground) and leg 3 is connected to a 3.5v trace with a 47.5 k resistor.

My thought was that maybe it was a repaired board and that was done in error and it was maybe pulling down the 3.5 v trace. Either way, it made no difference to the current issues. Hopefully it (IC) didn't get damaged if it was incorrect before. Wish I had another board to check.

[BCM_OC]

Re: lg 60ld550

Ok, that looks like what you should expect on that pin.

Well that's on pin 18 (INV-ON) on one side of the connector.

What I don't seem to have is 12v on 17, 19, and 21, which would correspond to "INV-ON" (17), "A-DIM" (19), and "P-DIM #1" (21)

I don't know which side on the mainboard connector is input and which side is output.

[dick_barton]

Re: lg 60ld550

You can check your voltages at the connector shown in post#8 where the names are given alongside the connector. See your 3rd & 4th photo of post#8.

[BCM_OC]

Re: lg 60ld550

You can check your voltages at the connector shown in post#8 where the names are given alongside the connector. See your 3rd & 4th photo of post#8.

I did. I just may not have explained it well enough.

Here is that 4th picture of the power supply connector again. If you look at at the three 12V terminals on the right side, I have 12v (11.7) there. However, on the opposing terminals on the left side of that connector I do not have any voltage.

[BCM_OC]

Re: lg 60ld550

Good catch. After posting the pics and schematics earlier, I just kept looking at the board and the schematic. I ended up taking that solder bridge off - as it didn't seem necessary for legs 1 and 2 (already going to ground) and leg 3 is connected to a 3.5v trace with a 47.5 k resistor.

My thought was that maybe it was a repaired board and that was done in error and it was maybe pulling down the 3.5 v trace. Either way, it made no difference to the current issues. Hopefully it (IC) didn't get damaged if it was incorrect before. Wish I had another board to check.

Here is a pic I found on Ebay of the same board. It is in the listing for a board repair service, and if you look closely at that IC (top, just left of center) you can see that it does not have any solder bridge between the terminals.

It's here; https://www.ebay.com/itm/Mail-in-Rep...Y-p:rk:26:pf:0

[dick_barton]

Re: lg 60ld550

I did. I just may not have explained it well enough.

Here is that 4th picture of the power supply connector again. If you look at at the three 12V terminals on the right side, I have 12v (11.7) there. However, on the opposing terminals on the left side of that connector I do not have any voltage.

Do you have the 24V and 3.3V supplies?

[nomoresonys]

Re: lg 60ld550

Maybe try heating with a hairdryer a small section at a time on powerboard, see if it comes on or there's any change, can also heat mainboard and inverter boards and see if it comes on or changes any.

[BCM_OC]

Re: lg 60ld550

Do you have the 24V and 3.3V supplies?

Yes.

Something funky is going on with that power supply though. I got a little tingle when I brushed up against one of the heat sinks. Stuck a meter on them and one is over 60 volts and the other is around 32 volts. (see pics) One of the outside legs on one of the mosfets is shorted to ground. Time to freshen it up I guess.

Somebody must make component kits for these, right? Any suggestions?

[BCM_OC]

Re: lg 60ld550

Maybe try heating with a hairdryer a small section at a time on powerboard, see if it comes on or there's any change, can also heat mainboard and inverter boards and see if it comes on or changes any.

I was really hoping to avoid that "repair" if possible. Need to see what I have here, though. At this point I'm not sure what's good and what isn't.