LG 50PC1DR doesn't power up. Just clicks.

[Lopdebif]

Hey everyone, I've got an LG 50PC1DR that my neighbor gave to me for fixing his lawn mower. He got it from his old boss, so I have no history on the TV.

Upon plugging it in, I hear the PSU click, red light on the front of the TV goes green, then another PSU click, then light goes back to standby red. (few LED's on the other boards turn on during this process, then turn back off). Pressing the power button simply does this again. Zero activity on the display, doesn't attempt to light up or anything.

I've removed and inspected the PSU board (and other boards in the TV without removing them yet) very carefully and have found no signs of bulging caps, no leakage, nothing burned or charred. The PSU just clicks, then clicks again a few seconds later and it does not cycle on its own. Only when I push the power button, click, ... click.

Unplugging the Y or Z SUS boards does nothing, same clicks, no changes.

I do have a digital multimeter, but I'm not sure where to place my ground when testing voltages. Any help is greatly appreciated. Thanks!

[tom66]

Re: LG 50PC1DR doesn't power up. Just clicks.

Your ground for your multimeter goes on the exposed metal chassis, the wall mount bracket is usually a good place.

Can you post some pictures of inside the set?

[Lopdebif]

Re: LG 50PC1DR doesn't power up. Just clicks.

You'll notice a sloppy solder job on the optocouplers, I bought a new iron and I'm undoing that as we speak. Not sure if I attempted the bridge correctly anyways.

[tom66]

Re: LG 50PC1DR doesn't power up. Just clicks.

OK, along the power connectors going to the main board, you'll see labels marked 19V... 5V... RL_ON... etc. Can we get a picture of these labels?

[Lopdebif]

Re: LG 50PC1DR doesn't power up. Just clicks.

Sorry about the delay, my digital camera couldn't have picked a worse time to start acting up.

[tom66]

Re: LG 50PC1DR doesn't power up. Just clicks.

OK, please measure the following pins while the set clicks on and off. Hold the measurement while it clicks, to see if the reading changes:

S-5V
RL-ON
AC-DET
6V
3.3ON
3.3V

To measure: all connectors installed. Multimeter black probe on chassis. Red probe to touch metal sheath around each pin visible on each connector.

[Lopdebif]

Re: LG 50PC1DR doesn't power up. Just clicks.

Thank you Tom for your time, here are the voltages:

S-5V - 4.82 - 5.02
RL-ON - 4.3 - 4.48
AC-DET - 4.66 - 4.85
6V - 5.67
3.3 ON - 3.82 - 4.27
and all 3 3.3V's tested at 3.31

They obviously bounce around a bit so I hope this will suffice.

That 3.3 ON seems a little high?

[tom66]

Re: LG 50PC1DR doesn't power up. Just clicks.

They are the same regardless of the clicking?

[Lopdebif]

Re: LG 50PC1DR doesn't power up. Just clicks.

Well when it clicks a second time (powering off) the voltages drop. Did you want me to test voltages after the second click? Like standby? Thanks!

[tom66]

Re: LG 50PC1DR doesn't power up. Just clicks.

Yes, please -- but right now, it looks like a main board problem as your voltages look fine.

[Lopdebif]

Re: LG 50PC1DR doesn't power up. Just clicks.

OK here we are:

S-5v - 5.02v standby, drops to 4.85v when powering up
RL-ON - .05v standby, 4.32v when powering up
AC-D - 4.83v standby, 4.65 when powering up
6V - standby, voltages slowly dropped, 5.62v when powering up
3.3 ON - .05v standby, 4.27v when powering up
3.3v - all 3 were .68v standby (seemed steady), 3.27v when powering up.

[tom66]

Re: LG 50PC1DR doesn't power up. Just clicks.

OK, near the top left of the power board, there is a connector going to the Y-sus.
On it there should be some pins marked Vs, Va, 5V, etc. Please make measurements there.

[Lopdebif]

Re: LG 50PC1DR doesn't power up. Just clicks.

Ok:

10-pin connector:

VS - all 3 voltages read -(negative) .2v upon turning the tv on, they went back to zero after 2nd click

NC: -.1v
GND (all 4): -.2v
VA: 4.5v
VA: 4.5v

and for the 4-wire connector:

GND: -.2v
GND: -.2v
5v: 4.75v
5v: 4.75v

I saw no "standby" voltages besides slow residual power drops.

[tom66]

Re: LG 50PC1DR doesn't power up. Just clicks.

OK, and if you unplug the Y and Z SUS do you note any change in those voltages?

[Lopdebif]

Re: LG 50PC1DR doesn't power up. Just clicks.

I believe the Z SUS wiring harness goes through the Y SUS? See the first photo I've posted above, the wires run above the PSU and behind the squirrel cage fan, to the Z board.

Upon unplugging the 10-wire and 4-wire harnesses that go to the Y SUS, the VS voltages yield no changes. However the VA voltages jump up to 56v! (from 4.5 with the harness connected). The panel sticker indicates 60v for VA and 196v for VS.

[tom66]

Re: LG 50PC1DR doesn't power up. Just clicks.

It sounds like you have a bad Vs and short on Va.

Let's try to rule out bad plasma panel short (which would terminate the repair, due to it being uneconomical to repair.)

Unplug the highlighted cables. Measure Va and Vs. Note: Under NO circumstances reconnect these cables with the TV power on or within 5 minutes of turning the TV off or else you will kill the plasma panel.

[Lopdebif]

Re: LG 50PC1DR doesn't power up. Just clicks.

Ok I've unplugged the two connectors you've circled.

With the 10-pin and 4-pin Y SUS connectors connected:

VS: (all 3) -.2v
VA: (both) 4.5v

With the 10-pin and 4-pin Y SUS connectors disconnected:

VS: (all 3) -.2v
VA: (both) jump to 56v

So no changes in behavior. The 2 connectors you circled are still disconnected as per your recommendation. Thanks so much for helping so far!

[tom66]

Re: LG 50PC1DR doesn't power up. Just clicks.

Hmm, it sounds like you may have two faults. Try with the Z-sus isolated and the Y-sus connected.

[Lopdebif]

Re: LG 50PC1DR doesn't power up. Just clicks.

Ok with the Z SUS board disconnected:

With 10-pin and 4-pin connectors connected to the Y SUS:
VS - 55v for all 3 (didn't register until the last second)
VA - 56v for both

With 10-pin and 4-pin connectors disconnected to the Y SUS
VS: -.2v for all 3
VA - 56v for both

[tom66]

Re: LG 50PC1DR doesn't power up. Just clicks.

VS = 55V?
Are you sure...? Please recheck. Vs should be 185V or so when working, if in error, I would expect Vs to be low but not equal to Va (may be a coincidence though...)