LG 37LH5000 boot loop due to shorted inverter

[tom66]

First time I had this. Inverter was shorted (fuse still OK.) As soon as inverter supply came up, TV rebooted, causing it to get stuck in a boot loop. Unplugging inverter allowed TV to power up fine with no backlight.

I found BD9215AFV burnt plus two FDP8447L MOSFETs shorted.

I am trying to source BD9215AFV now, the FETs were easy enough.

[stj]

Re: LG 37LH5000 boot loop due to shorted inverter

$9 for one
http://www.ebay.com/itm/201086770501

$38 for ten
http://www.ebay.com/itm/191066810286

[tom66]

Re: LG 37LH5000 boot loop due to shorted inverter

Yeah I saw that but I don't feel like waiting 2-3 weeks. I'm trying to find one closer to home.

[stj]

Re: LG 37LH5000 boot loop due to shorted inverter

digikey has them,
x for the chip, x x2 for the postage!

[tom66]

Re: LG 37LH5000 boot loop due to shorted inverter

Plus import fees... I got bit by that last time!

[vinceroger69]

Re: LG 37LH5000 boot loop due to shorted inverter

the only one i can see really in the uk is chs
http://www.chsinteractive.co.uk/elec...al-i-c-smd.htm
bit pricey and postage high imo.

[tom66]

Re: LG 37LH5000 boot loop due to shorted inverter

Have ordered from CHS, only UK source... Bloody expensive!

[vinceroger69]

Re: LG 37LH5000 boot loop due to shorted inverter

i tried the shop i use in birmingham too they didnt stock it either chs very expensive anyway hows you plasma still running good i hope?

[tom66]

Re: LG 37LH5000 boot loop due to shorted inverter

The Kuro is still working fine, I've since moved it into the new house.

[vinceroger69]

Re: LG 37LH5000 boot loop due to shorted inverter

cool that was a nice easy fix then also i hope you fix this lg inverter too with the price of that part!

[tom66]

Re: LG 37LH5000 boot loop due to shorted inverter

Hmm :/. I finally fixed the inverter issue, turned out there was a small 10k resistor O/C on the inverter board, feeding the STB pin of one of the BD9215AFV IC. It's only current limiting into an IO port, so I subbed it with a 22k and it worked. The TV turns on and the backlight lights, however, it makes a hideous buzzing sound (worse than chalkboard grating), and a portion of the screen does not light.

I suspect there is a short in the panel... bulb to chassis... yay...

I will have to take the panel apart to repair it.

[sven337]

Re: LG 37LH5000 boot loop due to shorted inverter

Hi,
I'm working on a similar inverter from a LG TV. The board is referenced 6632L-0549A, and it sports 4 transformers, 8 MOSFETs. The BD9215AFV was OK, but it was the slave chip BD9898FV that was dead, as well as three shorted MOSFETs.
I've replaced everything (replacing the BD9898FV was very tedious, I unfortunately destroyed a trace or two so had to fix things up with wire), and the inverter seems to at least start up, but it still doesn't appear to work.

Since I suspect you are working on the exact same board, I'm asking here:


There is a LED on the inverter which lights up for a short time when I power up the TV, then it appears to continue its "boot loop" just like before. Any idea what logic drives the LED?

There's also a strange part on the board, under a blob of glue, next to silkscreen that says "REG". Any idea what this can be?

I haven't yet looked at the "status" pin of the inverter, I suspect it's detecting a fault somehow (either because I botched my repair job or because some other part is broken) and telling the TV to stop.

What is this resistor you are talking about? What was the fault?

Thanks

[tom66]

Re: LG 37LH5000 boot loop due to shorted inverter

Are you sure the chips are different? I thought both were BD9215AFVs?

Mine still isn't working, the LED does now light up, I think it indicates the ignition phase for the bulbs but I haven't found any further info or documentation. In the middle of a house move, so won't be able to have a look at it again for a while.

[sven337]

Re: LG 37LH5000 boot loop due to shorted inverter

I'm sure the chips are different. BD9215AFV is the "master" (according to the datasheet), and BD9898FV is the "slave" (again, according to the datasheet, I'll confess not having given much attention to what those chips do exactly). BD9898FV burned when I tried to start the inverter with the broken MOSFETs removed (not the smartest idea on the planet, but I wasn't expecting the chip to blow...).
So I sourced it (with difficulty), and replaced it, and I get to the point where the LED lights up for about 1 second, then stops again.

I'm still hunting for documentation. Will post an update if I make any progress.

Note: I'm not sure what inverter you have, but 6632L-0549A appears to be replaceable (according to pictures) with 6632L-0579A, aka PNEL-T808B (vs T808A for 0549A). 0579A is somewhat easier to find a replacement for, in case this gets to the point where we can't actually fix the board.

[tom66]

Re: LG 37LH5000 boot loop due to shorted inverter

I have the 549.
That might explain why it isn't working, I swear it was a BD9215AFV for both... but then again it was badly burnt and I could not make out the part # completely.
I spent £11 on the chip from CHS... so I am a bit pissed if I bought the wrong one!!! (Ugh!)
I may go for swapping the inverter. From China it's about £25.

[sven337]

Re: LG 37LH5000 boot loop due to shorted inverter

This inverter's architecture is fairly complex compared to others.
If you need one, I managed to buy a BD9898FV at an unbeatable price: http://www.aliexpress.com/item/Bd989...080638181.html
Note the picture says BD9897FS (the most common single-chip driver for similar inverters), but the marking really is BD9898FV. Is it genuine, I don't know, since my inverter isn't working one can wonder

The 0579A is indeed about 25GBP (will you guys ever join eurozone?), and I'm pretty sure it's compatible with 0549A. The TV isn't mine however so it isn't my decision.

[stj]

Re: LG 37LH5000 boot loop due to shorted inverter

(will you guys ever join eurozone?)

NO, because then the government in the u.k. would not be able to run a printing-press 24 hours a day to hide the collapse.

[sven337]

Re: LG 37LH5000 boot loop due to shorted inverter

I wonder if the lamps themselves aren't bad. What's the likelihood that they'd be e.g. shorted?

What gives me trouble is that only one wire is actually connected from the lamp to the inverter! I don't know where the other one is, perhaps the chassis is used?

[tom66]

Re: LG 37LH5000 boot loop due to shorted inverter

This is always a possibility, practically the only way to be sure is to take the panel apart.

[sven337]

Re: LG 37LH5000 boot loop due to shorted inverter

Two of the three FETs I've replaced were shorted again after a few minutes of experimentation. Perhaps the lamps are bad, or the transformers - anyhow I give up. I may attempt to replace this inverter (6632L-0549A) with an apparently compatible, used 6632L-0579A, but I'm not sure this is worth the expense.