LG 42PC1D No Video

[mnow]

Got a LG 42PC1D with no video display!
Va and VS are normal and assume that Vy of 122v and VSC of 188V is normal also (might have those mixed up). Z board seems to be working as well.
So why no picture?

[maxvalutech]

Re: LG 42PC1D No Video

Yes.

[mmartell]

Re: LG 42PC1D No Video

IPM's ?

[mnow]

Re: LG 42PC1D No Video

Wouldn't the IPM be working if VSC and Yv are there?

[mnow]

Re: LG 42PC1D No Video

Can the Ysus board be checked without the drivers connected? Need to measure voltages at different pinouts to verify IPM!

[mnow]

Re: LG 42PC1D No Video

OK, Just scoped the Y outputs and there is signal there with -Vy @ 200v, VSC @ 120v. On the Z board, signal also scoped with a Z-bias of 100v and no picture on the screen. Is it possible the sacreen could be bad?

[mnow]

Re: LG 42PC1D No Video

Anyone have some input to this problem?

[Andrew F. Ali]

Re: LG 42PC1D No Video

Are the voltages on the label the same as those you measure. Vs, Va, etc?

[mnow]

Re: LG 42PC1D No Video

All voltages at normal rating! Scoped the Ysus driver and Zsus boards and all signals appear normal. I do however have one red LED on the logic board (all others are green).

[Wilderone]

Re: LG 42PC1D No Video

Do you have any glow on the panel when the TV is powered on?

[Andrew F. Ali]

Re: LG 42PC1D No Video

the vital signs are OK. A red LED on the Logic Bd. is indication of a problem there. Either it is not getting a healthy 5V supply or some other component malfunction.

[mnow]

Re: LG 42PC1D No Video

No glow on the panel at all Wilderone.
Yes I agree that red is bad. All the power rails are at spec and clean DC.
If only could find a service manual on this, would help greatly.

[Andrew F. Ali]

Re: LG 42PC1D No Video

Look at the CTRL Bd and search for 2 pins/holes labeled AUTO-GEN. Disconnect the Main Bd. from the CTRL Bd. Solder/connect a jumper between the AUTO-GEN pins/holes. Apply the ac and if the Panel is good the Test Patterns should show. If the screen shows a perfect White display, then the Panel is OK and your Main Bd. or LVDS cables is the fault.

[mnow]

Re: LG 42PC1D No Video

Thanks Andrew, will try that tomorrow.

[mnow]

Re: LG 42PC1D No Video

Finally got to that TV and found the auto-gen, problem is that it is a 4 pin header and not sure which pins need to connect.

[R_J]

Re: LG 42PC1D No Video

The center 2 pins are common, I would think either pin 2or3 to pin4. Other ctrl boards auto_gen connect the 2 pins with the resistors off them.

[mnow]

Re: LG 42PC1D No Video

OK, Jumpered pins 3 and 4 on auto-gen header with and without LVDS cable connected. Still black screen! The only difference noted was that LED 1 and 3 came on in the CTRL board rather than LED 2 and 3 without the jumper. They are outlined in red.

[Markus1]

Re: LG 42PC1D No Video

If only could find a service manual on this, would help greatly.

You can find the Service Manual under this address:

https://archive.org/stream/LG_42PC1D#page/n0/mode/2up

Hope it works.

[mnow]

Re: LG 42PC1D No Video

Unfortunately incomplete just like all the other schems out there!
Does not show the complete picture.

[Andrew F. Ali]

Re: LG 42PC1D No Video

To do the AutoGen test, you have to disconnect the PSU from the Main Bd. and the Main Bd. from the CTRL Bd. Then you would have to put the PSU in Self-test mode to turn it on.