LG 32LC2D - Power supply with burnt IC

[Ken Laszlo]

Hi Folks

I recently acquired one of these sets very cheaply with a known fault.
The fault was that the set would not turn on. The seller also said that before that, they had lost sound on the set, and that they have been using an external sound system.

Hoping that it may be a simple case of replacing some bad capacitors, I took the power supply board out - Many of the main capacitors are bulging, just as I suspected but looking on the back of the board has revealed something nasty.

(See photo)

It looks like one of the surface mount ICs relating to the power has burnt out.

My question to you now is . . . is it worth attempting a further repair of this board, and replace the bulging capacitors (and the IC), or should I just try to get a replacement power board?

Also, could the blown IC that is visible here have caused damage to the other boards?

Thank you
Chris

[michael dranfield]

Re: LG 32LC2D - Power supply with burnt IC

I think I have had this fault before and the 8 pin chip you refer to is a MOSFET that is just used as a power switch to switch off the rail to the sound output stage , however a photo of the other side of the board would be very useful in identifying the psu .

[Ken Laszlo]

Re: LG 32LC2D - Power supply with burnt IC

I appreciate the reply, Michael.

As you request, a few more photos of the PSU board.
I marked all original capacitors with an X for my own purposes.
I cleaned up the burn mark off the board.

I would not trust the other IC next to the one burnt out either (another MOSFET perhaps?), as it looks like it may also be damaged due to heat. Some of the plastic is raised up off the top of it.

The power supply board model number reads LGLP2637HEP.
PCB number stamped on the top reads 68709D0006B Rev 1.2

Thanks again
Chris

[ReeceyBurger123]

Re: LG 32LC2D - Power supply with burnt IC

You need to replace every cap on that Psu apart from the primary units. Also whats the circuit ref of that Ic ? I would say it burnt up because of the badcaps letting too much ripple current through thats why you never ignore badcaps.

[Ken Laszlo]

Re: LG 32LC2D - Power supply with burnt IC

Sounds like excellent advice to me, ReecyBurger.

My searches reveal that the burnt-out IC at position Q209 is a IRF7807, 30V N-Channel Mosfet. The suspect one next to it is Q210, IRF7807z Mosfet.

Chris

[budm]

Re: LG 32LC2D - Power supply with burnt IC

You should also do the resistance test between the output Voltage pin and GND that goes to the sound output power amp ICs to see if it shows very low resistance otherwise you will be blowing the parts due to shorted parts in the main board.

[Ken Laszlo]

Re: LG 32LC2D - Power supply with burnt IC

Thanks, BudM - I will do.

In my travels, I found this very useful image.
I also had my jaw drop at the price of 130C capacitors (£5 each).

Chris

[Ken Laszlo]

Re: LG 32LC2D - Power supply with burnt IC

Thanks for all your input.
I had a look at the costs involved and decided to buy a complete 2nd user 'known working' power supply off eBay, which has cost less than all the replacement components combined (not to mention the additional work and hassle).

Thank you again, BudM for the pointer about checking if there is a short-circuit relating to the Audio power IC- I'll do this when I have a moment, and well-before I put in any replacement PSU. I know audio issues are very common in these LG sets. Is it common for the Audio Power IC's to go short-circuit?

Happy to hear any other advice or tips as I go further into repairing this set.

Chris

[vinceroger69]

Re: LG 32LC2D - Power supply with burnt IC

Hi for capacitors i use
http://cpc.farnell.com/
i usually use fc/fm/fr panasonics the prices from cpc are very good and atleast there genuine parts as if you buy from ebay etc some are fakes.

[joe-joe]

Re: LG 32LC2D - Power supply with burnt IC

hallo,
i have the same problem with my LG
the 6 V is missing!
i got a advice to replace Q209 and Q210= fet s
and U 204 =IRU 3037?
i have doubts about the last one?
anyone has experiens with it??
thanks