LG 42PQ6000 - "overlying" blue tint

[armando]

Re: LG 42PQ6000 - "overlying" blue tint

I finally managed to press the instop button.
The screen showed the message "do not unplug" and the set powered off (switching to stand-by mode, with the red IR light on). I waited a while and nothing happened. After 5 minutes I turned on with the remote and I got the initial sequence ("thank you for choosing LG", choice of language, channel search...).
During all these operations colours (menu dialogs) were ok but sadly, when the tuning ended and the set switched to channel 1, the "blue veil" was still there.

I noticed that during the second half of the tuning, when searching for (missing) analog sources, the typical "snow effect" all over the screen was not bluish. So it seems that the... blue effect takes on only when digital channels (or usb files) are to be shown.

As a further (last?) attempt, I also upgraded the firmware. The upgrade looked flawless, but the blue image is still there.

While thanking you again for your kind and useful help, I have to say I still can't believe an hardware issue can arise from a simple video file reading. It seems to me quite a worrying assumption.
Or maybe it was only a really much curious coincidence and the hardware failure had nothing to do with the usb stick or the file reading; in which case I have to admit I expected this tv set, which was highly rated (and priced) at the time, to last a few years longer. :]

[tom66]

Re: LG 42PQ6000 - "overlying" blue tint

I am almost certain your issue is with the main board in some way. You could try reflowing it, although that is usually a temporary fix at best.

[armando]

Re: LG 42PQ6000 - "overlying" blue tint

I am almost certain your issue is with the main board in some way. You could try reflowing it, although that is usually a temporary fix at best.

At this point I also tend to be certain about that, unless there are some other (heavier, lower level) "resets" which require special equipment.
Sorry for my ignorance: what do you mean with "reflowing"?
When you say it's a temporary fix at best, are you suggesting I'd better forget this set and start looking for a new one?

PS. From your technical point of view, what do you think such a main board failure can be caused by? Are all modern tv sets so... fragile?

[tom66]

Re: LG 42PQ6000 - "overlying" blue tint

The most common cause of a failure like this is a soldering defect around one of the balls on the processors on the main board. Often if this defect occurs the processors will malfunction in some way, it depends on the exact location. The balls are hidden under the processor so are not accessible. By heating up the entire board to around 250C, it is possible to cause some of the solder to re-heat and a new connection may be made. This is often temporary, because the solder may crack again, but it can give another year or two's life to the board.

A correct "reflow and reball" operation involves removing the processor entirely, replacing the solder balls with leaded types and then refitting the processor. Not an amateur job, but it is likely to last for the rest of the life of the television if done correctly.

[armando]

Re: LG 42PQ6000 - "overlying" blue tint

Thanks a lot for your kind explanation.
I actually already read something like that (apart from the word "reflowing") last year, when investigating the failure of a laptop's video card which had proved commonly defective on a whole lot of computers produced in a certain month.
What surprises me, about this tv set, is the idea that a soldering defect can arise after more than 8 years of flawless operation and during a quite normal viewing session, moreover with no power lags or fluctuation at all (the set is fed via a sine wave UPS).

Anyway, do you think a standard LG service center could "correctly" perform such a delicate removing/replacing/refitting operation, also without charging it... half the price of a new tv? :]

[tom66]

Re: LG 42PQ6000 - "overlying" blue tint

Thanks a lot for your kind explanation.
I actually already read something like that (apart from the word "reflowing") last year, when investigating the failure of a laptop's video card which had proved commonly defective on a whole lot of computers produced in a certain month.
What surprises me, about this tv set, is the idea that a soldering defect can arise after more than 8 years of flawless operation and during a quite normal viewing session, moreover with no power lags or fluctuation at all (the set is fed via a sine wave UPS).

Anyway, do you think a standard LG service center could "correctly" perform such a delicate removing/replacing/refitting operation, also without charging it... half the price of a new tv? :]

Soldering defects primarily arise due to temperature cycles and also electrochemical properties of solder (if interested look into "tin whiskers")

I don't know where you live, but my experience with service centres has been poor. So, your mileage may vary. Prices are often high as well.

[armando]

Re: LG 42PQ6000 - "overlying" blue tint

So, as a very last attempt before... the rubbish dump, I maybe could try to locate the faulty board and see if I can get a spare one.
I understand I may look stubborn; the fact is I'm sorry to scrap a large plasma panel that still, despite the low resolution, gives an image of higher quality than many other more "modern" panels.

I know I could, if I was skilled enough, try to repair the board myself, but I'm afraid such a task is honestly beyond my reach.
Do you think I have any actual chance, removing the back cover, to correctly spot the responsible board, thus avoiding the risk of buying a wrong spare part?
By the way, I just recalled that when the tv stopped at first (while watching the USB file), before I started resetting and so on, I got some messages saying "input blocked".

PS. I looked into "tin whiskers". Thanks for the hint.
Quite interesting. Quite... disturbing, as well. :]

[vinceroger69]

Re: LG 42PQ6000 - "overlying" blue tint

yes if you remove the back cover and take a good clear picture of the boards that are used in your set we should be able too help you find the correct part.

[armando]

Re: LG 42PQ6000 - "overlying" blue tint

I'll try to arrange a suitable working space where to proceed with the removal and the pictures.

In the mean time, I'd be thankful to any technician telling me if (and how) an hardware failure like this can be triggered by a simple USB video file playing. Does that make any sense from a technical point of view? Do such things happen normally? Are they to be expected?

I know at this point it makes no difference, but I always assumed that hardware and software were... separate worlds and that normal user-level software operation never could produce hardware damage. Is that assumption wrong?

[Th3_uN1Qu3]

Re: LG 42PQ6000 - "overlying" blue tint

normal user-level software operation never could produce hardware damage. Is that assumption wrong?

The CPU is divided into several blocks. Not all of them are required/active at the same time, so the CPU's power consumption and heat output varies depending on what it's asked to do.

It is possible that playing a video off the USB drive, which requires the internal video decoder, led to a higher power consumption and overheated the chip. LG is known for skimping on heatsinks in their TVs.

I have a 55LE5500 main board with a partially failed CPU that will work as a regular TV or monitor just fine, but if I try to play a video from USB, it will show a garbled picture and continuously restart the video from the beginning.

[armando]

Re: LG 42PQ6000 - "overlying" blue tint

... It is possible that playing a video off the USB drive, which requires the internal video decoder, led to a higher power consumption and overheated the chip. LG is known for skimping on heatsinks in their TVs.

Thanks for your answer, which seems to me a quite convincing explanation. The strange thing is that the failure occurred at the very beginning of the file playback, when the internal video decoder had supposedly just started working (and warming up). Morevover, it was the first file played that night, so the decoder had no reason to be already hot.
Anyway, this explanation of yours may make sense from a wider point of view, as we actually started using the USB port only almost a year ago, gradually increasing the frequency, while in the previous years the USB port was nearly unused, so the "skimpiness" of the manufacturer had no way to... show up.

I have a 55LE5500 main board with a partially failed CPU that will work as a regular TV or monitor just fine, but if I try to play a video from USB, it will show a garbled picture and continuously restart the video from the beginning.

I appear to be more... lucky, as my TV shows its blueish picture always, whatever the source. Colours are correct only when menus are displayed, which proves (kind of mockery, I would say :] ) the plasma panel to be ok.

[budwich]

Re: LG 42PQ6000 - "overlying" blue tint

are you using a usb "stick" or a usb interface to an external hard drive?

[Diah]

Re: LG 42PQ6000 - "overlying" blue tint

with same apk you send INSTOP send to the TV INSTART and upload photo on the screen shoot
if the Tuner Module Type changed by SM will give likly the issue you described after INSTOP

[armando]

Re: LG 42PQ6000 - "overlying" blue tint

are you using a usb "stick" or a usb interface to an external hard drive?

When the failure occurred I was using a 2GB stick, the same I had been using for 6 months or more with no problems.
Later I also tried with a self-powered external hard drive.
With both devices the playback runs normally, but the blue tint is always there.

[armando]

Re: LG 42PQ6000 - "overlying" blue tint

with same apk you send INSTOP send to the TV INSTART and upload photo on the screen shoot
if the Tuner Module Type changed by SM will give likly the issue you described after INSTOP

I'm afraid I didn't quite understand the meaning of "changed by SM".
Anyway I'll try to send the INSTART and upload the screenshot.

[armando]

Re: LG 42PQ6000 - "overlying" blue tint

Here it is.
You can also see the lovely blue special effect in the background. :]

[armando]

Re: LG 42PQ6000 - "overlying" blue tint

Here are other photos, from the inside.
I noticed the central board main chip is marked "XD". As the TV, when in Demo mode, shows correct colours in the "XD off" (right) half screen, maybe the fault is there?