LG 42LB5600 TV with faulty EAX65423701 PSU

[Dannyx]

Re: LG 42LB5600 TV with faulty EAX65423701 PSU

Ever thought about to measure the current draw of the main board? Maybe it draws more that the VSB rail of the PSU can handle? So put that main board back on the PSU and retest.

Also check the main board VSB rail with your ohm meter between the GND and VSB rail, maybe there is a short? Check the others too on the main board.

Ok, there's definitely a short on the main board between 3VSB and GND. Now I feel like an idiot....where do I start ? I posted some pics of the area of interest of the main board. The 3VSB trace run underneath the board and to that IC403, which is a 5432 TI47A P2M363 (that's what it says on it from top to bottom - it's not very clear in the close-up). Couldn't find anything about this thing.....I assume it's a buck/boost converter, since I see a coil next to it. I'll try pulling it out anyhow to see if the short goes away. Then we've got IC404 which is a regulator and doesn't read any shorts between its pins. The board itself is an EAX65361505. Cheers and thanks again.

[Dannyx]

Re: LG 42LB5600 TV with faulty EAX65361505 main board

Here are the pics of the area of the main board where I THINK the fault lies. At the top, you can see the power connector. The 5VSB pins are the second and third ones from the right of that connector. I also tried a close-up of that IC if it's of any help....turned out pretty sh!t, so I apologize for that.

[vinceroger69]

Re: LG 42LB5600 TV with faulty EAX65423701 PSU

can you try using a low voltage and freeze spray and see what part heats up?

[Th3_uN1Qu3]

Re: LG 42LB5600 TV with faulty EAX65423701 PSU

Try a large cellphone battery, should make something smoke rather quickly. 3.7v should not harm any good parts on that rail.

[Dannyx]

Re: LG 42LB5600 TV with faulty EAX65423701 PSU

can you try using a low voltage and freeze spray and see what part heats up?

Pulled out that IC and the short's still there. I don't have a can of spray on me right now sadly...will try it soon. In the meantime, I'll keep looking around.

[dick_barton]

Re: LG 42LB5600 TV with faulty EAX65423701 PSU

The smd in the red box does not look healthy but it could be flux on top of it. Can you measure it's resistance using your meter probes across it.

[Dannyx]

Re: LG 42LB5600 TV with faulty EAX65423701 PSU

The smd in the red box does not look healthy but it could be flux on top of it. Can you measure it's resistance using your meter probes across it.

That's a zener diode which I initially removed and put back after measuring and reading ok. The short's still there even with that diode, EEPROM chip (the one with the yellow dot at the bottom) and that mystery IC removed, so I'm starting to think there's a short in the CPU itself...just a hunch :|

[dick_barton]

Re: LG 42LB5600 TV with faulty EAX65423701 PSU

I would use my meter on ohms and check all the smd capacitors for short.

The earlier suggestion of using a variable power supply and bringing the voltage up on that supply rail slowly from 0V which would heat up the offending component is the only other simple method.

[Th3_uN1Qu3]

Re: LG 42LB5600 TV with faulty EAX65423701 PSU

Unfortunately shorted CPU is common if there has been a surge thru one of the HDMI ports. Cheap set-top boxes are known to do that.

[Dannyx]

Re: LG 42LB5600 TV with faulty EAX65423701 PSU

I would use my meter on ohms and check all the smd capacitors for short.

The earlier suggestion of using a variable power supply and bringing the voltage up on that supply rail slowly from 0V which would heat up the offending component is the only other simple method.

Trouble is that if I do that they ALL seem to register a short, since they go between 3v and GND, so if there's a short somewhere else, it will show up through every component.....at least that's what I think.

[Th3_uN1Qu3]

Re: LG 42LB5600 TV with faulty EAX65423701 PSU

Yes. Inject current and see what gets hot.

[CapLeaker]

Re: LG 42LB5600 TV with faulty EAX65423701 PSU

Trouble is that if I do that they ALL seem to register a short, since they go between 3v and GND, so if there's a short somewhere else, it will show up through every component.....at least that's what I think.

Quite right on parallel things in a circuit, but yet not. If you have a sensitive Ohm meter that can measure very small amounts of resistance, then this isn't an issue. There are devices actually made for that. Google "Leakseeker 89" for example.

Instead of freeze spray and injecting current, you also can use 99% rubbing alcohol and inject current. Yep, the alcohol will evaporate faster where it is hot.

Once you inject like 3V and 2A and that main IC get's hot, that's gonna be about it.

[angel-boy]

Re: LG 42LB5600 TV with faulty EAX65423701 PSU

I notice that this tv from this post arrive in my service with supposed PSU problem , but after check the tv the problem is with mainboard ( logic board ) , seems like the XD Engine LGE 2134 fault.

But Ic403 and IC1300 was removed . Only think to do , replace digital board.

[dick_barton]

Re: LG 42LB5600 TV with faulty EAX65423701 PSU

Trouble is that if I do that they ALL seem to register a short, since they go between 3v and GND, so if there's a short somewhere else, it will show up through every component.....at least that's what I think.

No so. For example if you put 2 x 1K ohm resistors in parallel and a piece of wire with a resistance of 0.5 ohms (to act as the short) also in parallel with them then although the resistors now look as though they are short circuited, if you put a voltage across them say of 1V, the short circuit piece of wire will draw approx 2 Amps. The resistors will still only draw a max of 1mA each (1V/1K). Total current through the circuit 2.002A

Hope I got that right.

[Dannyx]

Re: LG 42LB5600 TV with faulty EAX65423701 PSU

I notice that this tv from this post arrive in my service with supposed PSU problem , but after check the tv the problem is with mainboard ( logic board ) , seems like the XD Engine LGE 2134 fault.

But Ic403 and IC1300 was removed . Only think to do , replace digital board.

That's exactly the same issue I had - pulled out the two ICs (the EEPROM and the buck regulator) and short was still there. Tell me: did your power LED also flicker like mine did ?

[angel-boy]

Re: LG 42LB5600 TV with faulty EAX65423701 PSU

I belive is the same TV, i`m from Constanta to. I dont remove any IC from board, only test the XD ic and is fault.

The mainboard will arrive tomorrow , and hope to finish this TV.

[Dannyx]

Re: LG 42LB5600 TV with faulty EAX65423701 PSU

I belive is the same TV, i`m from Constanta to. I dont remove any IC from board, only test the XD ic and is fault.

The mainboard will arrive tomorrow , and hope to finish this TV.

Yeah, dead CPU most likely...hunks of junk >_>

[angel-boy]

Re: LG 42LB5600 TV with faulty EAX65423701 PSU

The TV works again.

[Dannyx]

Re: LG 42LB5600 TV with faulty EAX65423701 PSU

The TV works again.

Never got to fix mine though - client refused and took it back.....fine, I said )

[angel-boy]

Re: LG 42LB5600 TV with faulty EAX65423701 PSU

I belive is the same TV, i`m from Constanta too.