LG 42LW450U mainboard MICOM SoC_Reset holding processor in reset?

[jesterace]

Hi,
I'm troubleshooting another TV that has no backlight or picture. Standby light comes on, and TV can be turned on with all PSU voltages available. I've followed the procedures to jump start the backlight, and that works ok but there was still no picture.

All PSU voltages appear normal.

Suspected mainboard and have been following the schematics checking voltages. Haven't found any missing voltages on the mainboard but have discovered that it's a MICOM microcontroller that starts the TV up. It's sending the PSU turn on signal ok, but the INV_CTL or (INV_ON) is 0v.

My main question is about a pin labelled SoC_Reset on the MICOM chip. It's reading 0v.

From my bit of experience fixing laptops, i'm guessing i'm right in thinking the main processor/video chip is being held in reset (problem)?

Just wondered if anyone encountered this before?

I suppose signals like the INV_ON signal from MICOM gets sent out after the reset it pulled away from SoC??

Cheers,
James.

[CapLeaker]

Re: LG 42LW450U mainboard MICOM SoC_Reset holding processor in reset?

what are the numbers on that chip so we can pull the specs hopefully.

[jesterace]

Re: LG 42LW450U mainboard MICOM SoC_Reset holding processor in reset?

number of chip is uPD78F0514

I read a bit about it in one document but from how i understood, the pin used for this SoC_Reset is a programmable in/out pin. Not sure if it's programmed to be active low or what in this TV.

[CapLeaker]

Re: LG 42LW450U mainboard MICOM SoC_Reset holding processor in reset?

that's the question I don't know either. You can try cutting the trace, lift a pin, tracing the reset trace etc.

[jesterace]

Re: LG 42LW450U mainboard MICOM SoC_Reset holding processor in reset?

yep think i'll follow it, maybe cut the trace and see what happens if i pull the reset high.

I suppose considering the PS_ON signal is coming out of the MICOM, the EEPROM/data is probably in good shape?

[ngth82]

Re: LG 42LW450U mainboard MICOM SoC_Reset holding processor in reset?

My appologies for resurrecting an old thread, but were you able to diagnose what was wrong with your MICOM? I have the same issue that is being tracked in a new thread for a 55LV5500. Your response would be greatly appreciated and any insight into fixing your current issue would help me (and others!) out.

Thank you,
Thomas

[TLFonderie]

Re: LG 42LW450U mainboard MICOM SoC_Reset holding processor in reset?

I'd like to resurrect this thread too. I have the 42LW450U that has not picture. I found out that the MOFSET Q601 is dead. I would like to order two new ones (I'll replace Q602 while I am there).
I never ordered MOFSETs before.
What I can read on them is
18NM60N
GK2AR V6
CHN 039
apparently from ST Micro from the logo.

Someone could tell me where I can buy this by unit? Thanks... and keep all feeding the badcaps community!

[petehall347]

Re: LG 42LW450U mainboard MICOM SoC_Reset holding processor in reset?

https://uk.rs-online.com/web/c/semic...384E4D36304E26

[budm]

Re: LG 42LW450U mainboard MICOM SoC_Reset holding processor in reset?

BTW, What is the P/N of the IC that the GATE of the failed MOSFET connected too? When that MOSFET went out it could have taken out the Gate driver circuit inside the IC with it so your newly installed MOSFET can be damaged.

[TLFonderie]

Re: LG 42LW450U mainboard MICOM SoC_Reset holding processor in reset?

https://uk.rs-online.com/web/c/semic...384E4D36304E26

Thanks Peter... I studied mechanics so my knowledge in electronics is limited. But I want to learn.
So my question might be silly but there are 4 different MOFSETs on the link that you provided. How do I know which one is the one I am looking for? Will the 4 of them do the job?

[TLFonderie]

Re: LG 42LW450U mainboard MICOM SoC_Reset holding processor in reset?

BTW, What is the P/N of the IC that the GATE of the failed MOSFET connected too? When that MOSFET went out it could have taken out the Gate driver circuit inside the IC with it so your newly installed MOSFET can be damaged.

Hi Budm,
As mentioned in my previous post, I have a limited knowledge in electronics but I am willing to learn. So thank you both for your help. I will put in pictures of the board so maybe you can tell me if I am wrong.
As far as I can see, there is only one IC near the MOFSETs. One of it's branch is going to a strange MOFSET that has only two branches, not three, and this MOFSET seems to feed the triger (middle) branch of the MOFSET.
Hopefully my explanations make sense.

If that IC needs to be changed, that will be a soldering challenge because it's quite small.

I'll post the pictures in a minute.

[TLFonderie]

Re: LG 42LW450U mainboard MICOM SoC_Reset holding processor in reset?

Here are the pictures










I put a red square around the faulty MOFSET on the last picture

[petehall347]

Re: LG 42LW450U mainboard MICOM SoC_Reset holding processor in reset?

Thanks Peter... I studied mechanics so my knowledge in electronics is limited. But I want to learn.
So my question might be silly but there are 4 different MOFSETs on the link that you provided. How do I know which one is the one I am looking for? Will the 4 of them do the job?

pick the one that looks the same as yours . there are 3 different case styles

[TLFonderie]

Re: LG 42LW450U mainboard MICOM SoC_Reset holding processor in reset?

pick the one that looks the same as yours . there are 3 different case styles

Yes you're right, the first one is the one as it has the tread for the screw to the heat bridge

[budm]

Re: LG 42LW450U mainboard MICOM SoC_Reset holding processor in reset?

Pictures are low res so I cannot even read the P/N of the PCBA.
That section where the MOSFET is si the PFC section.

[TLFonderie]

Re: LG 42LW450U mainboard MICOM SoC_Reset holding processor in reset?

Sorry about the low resolution, the pics have been resized when I added them into my badcaps account. The PCB part numbers are PCB P/N EAX62865401/8 (rev 1.0 2010.11.19) LG P/N EAY62169801
Funny enough it has two part numbers...

[budm]

Re: LG 42LW450U mainboard MICOM SoC_Reset holding processor in reset?

EAX???? (printed directly on the board) is the PCB (Blank circuit board without parts installed)
EAY??? (on the barcode sticker) is the PCB Assembly which is the PCB stuff with the required parts to make PCB Assembly for particular model, countries, ECT.
http://www.shopjimmy.com/lg-eay62169...upply-unit.htm
LG EAY62169801 (EAX62865401/8) Power Supply.
Pictures provided by shojimmy.
Please see if this is the same as your board.
BTW, those two MOSFETs are for the PFC Voltage booster circuit, they are bascially connected in parallel, the one device with two leg is the diode for the PFC.
The SMD IC close to the MOSFETs is the PFC Controller IC, P/N?
So when you say the MOSFET is dead what exactly do you mean? It has very very low resistance between S and D pin? If it is shorted or has very low resistance the main AC fuse should have blown too.
The more details as what TV/Board not doing the better.

[TLFonderie]

Re: LG 42LW450U mainboard MICOM SoC_Reset holding processor in reset?

EAX???? (printed directly on the board) is the PCB (Blank circuit board without parts installed)
EAY??? (on the barcode sticker) is the PCB Assembly which is the PCB stuff with the required parts to make PCB Assembly for particular model, countries, ECT.
http://www.shopjimmy.com/lg-eay62169...upply-unit.htm
LG EAY62169801 (EAX62865401/8) Power Supply.
Pictures provided by shojimmy.
Please see if this is the same as your board.
BTW, those two MOSFETs are for the PFC Voltage booster circuit, they are bascially connected in parallel, the one device with two leg is the diode for the PFC.
The SMD IC close to the MOSFETs is the PFC Controller IC, P/N?
So when you say the MOSFET is dead what exactly do you mean? It has very very low resistance between S and D pin? If it is shorted or has very low resistance the main AC fuse should have blown too.
The more details as what TV/Board not doing the better.

Actually, both EAX??? and EAY??? are printed on board. I have another number on the sticker, which BB2HD62169811056 (1.4)
I also found another part number printed on the card, which is LGP4247-11SLPB
Unfortunately as I am located in Europe, I do not have access to shopjimmy, the access is prohibited for some reason.

Anyway, I detached the MOFSETs and tested them... and I was wrong, both seem to work (tested with my tester on "Diode" mode).

So I plugged the 220V input cable and measured the output lines of the card. The led feeding lines are all at 5.1V. The motherboard feeding line has 3.5V where indicate, but has 0V on the 12V lines (PWM, N.C., DRY-ON) and the 24V lines as well (24V, PWR-ON).

One weird thing is that when I put my multimeter in alternative voltage position and I put only my minus wire on the ground of the card (on one of the screws), I get a 12V reading without having the positive wire touching any component...

[R_J]

Re: LG 42LW450U mainboard MICOM SoC_Reset holding processor in reset?

Your led voltage (118 vdc) comes from D206, filtered by C212 & C213 and feeds one lead of the led's. The return lines are controlled by the led driver sub board

[R_J]

Re: LG 42LW450U mainboard MICOM SoC_Reset holding processor in reset?

Ops... Ignore my post #19, wrong thread

As for this thread, Check your P201 PWR-ON pin, that pin turns the power supply on and off and I believe needs to be (high) to turn on the board.
To test the power supply, disconnect the cable between P201 and the main board, then get about a 1k resistor and connect it between 3.5v and POW-ON, that should give you +12v and +24v