LG 42PN5400 Plasma has strange intermittent issue

[SurrealMustard]

This thing is turning out to be tough to troubleshoot. The baseline symptom is that it'll power on and light up the screen, but do nothing else. When I went to test it, I placed the panel face down on the table, remove the back cover, and attempt to measure voltages. The voltages measured normally, so I lifted the panel up to take a look at it, and it was displaying the "no signal" screen.

Following this, I put it back on its stand and was unable to get it to stop working again for a couple of weeks. After that time, the same thing happened again. Any ideas as to what could be causing this issue without having a way to reliably troubleshoot it?

[tvtimmy]

Re: LG 42PN5400 Plasma has strange intermittent issue

Run it through the test patterens and try to make it screw up. I got a feeling the main board is about to go totally out.

[dick_barton]

Re: LG 42PN5400 Plasma has strange intermittent issue

If it's movement then I would ensure, as tvtimmy says, that all screws are tightened but also all the connectors are firmly in place.

[SurrealMustard]

Troubleshooting progress

Run it through the test patterens and try to make it screw up. I got a feeling the main board is about to go totally out.

Do you know the procedure to invoke the test patterns on this model? I ran a web search and didn't find much.

If it's movement then I would ensure, as tvtimmy says, that all screws are tightened but also all the connectors are firmly in place.

A brief inspection yielded no noteworthy loose screws or connections on any of the boards. One of the corner screws on the mainboard was a tiny bit loose, but nothing too crazy.

[dick_barton]

Re: LG 42PN5400 Plasma has strange intermittent issue

As far as I can recall for plasma sets reading the forum, disconnect the ribbon from the mainboard going to the control logic board and short the two pin marked auto-gen on the control logic board using a piece of wire or paper clip and switch on.
If it's a service mode test pattern your looking for then sorry I don't know.

[SurrealMustard]

New details

As far as I can recall for plasma sets reading the forum, disconnect the ribbon from the mainboard going to the control logic board and short the two pin marked auto-gen on the control logic board using a piece of wire or paper clip and switch on.
If it's a service mode test pattern your looking for then sorry I don't know.

I'll give it a try, but in the meantime, I've got some more details on the symptoms. I left it plugged in over the weekend, and when I went to power it up on Sunday, it was locked up. Cutting the power and trying again allowed it to work. Today, I powered it up and left it for a little bit, and when I went back, the panel was on, but blank and the set was once again locked up.

I'll try the AUTOGEN trick tomorrow and see if anything different happens.

[ReeceyBurger123]

Re: LG 42PN5400 Plasma has strange intermittent issue

Mainboard fault, easy diagnoses.

[SurrealMustard]

Test patterns abound!

Got test patterns on the second try with EXT_AUTOGEN. I think the only reason it didn't work on the first try was because I didn't have the jumper attached quite right. I'll pursue the purchase of a mainboard for this thing next.