Author Topic: EEVblog #763 - Dumpster Plasma TV Bad Cap Repair  (Read 13105 times)

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Offline EEVblog

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EEVblog #763 - Dumpster Plasma TV Bad Cap Repair
« on: July 08, 2015, 10:43:23 am »
Dave & David2 replace the bad caps in the old LG 50PF3DF 50" plasma TV found in the dumpster here:

Will it fix the problems?
Also an impromptu tutorial on how to replace bad/leaking/bulging capacitors, and measuring capacitor ESR in-circuit.
Plus bonus banter.

Teardown here:

PCB Sparkgaps:


 

Offline cpuerror

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Re: EEVblog #763 - Dumpster Plasma TV Bad Cap Repair
« Reply #1 on: July 08, 2015, 11:17:08 am »
Some of those vertical lines might go away after the tv has displayed some variable content such as a tv show. Plasmas will have image retention, and will retain an image indefinitely if simply left off. However, unlike burn in, the retained image fades away as soon as there is moving content on the screen.
 

Offline Ribster

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Re: EEVblog #763 - Dumpster Plasma TV Bad Cap Repair
« Reply #2 on: July 08, 2015, 11:19:42 am »
I saw at 8:45 that you accidentally measured the ESR with the wrong polarity. Should that effect the ESR measurement ?
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Offline EEVblog

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Re: EEVblog #763 - Dumpster Plasma TV Bad Cap Repair
« Reply #3 on: July 08, 2015, 12:13:11 pm »
I saw at 8:45 that you accidentally measured the ESR with the wrong polarity. Should that effect the ESR measurement ?

No, it doesn't matter.
 

Offline EEVblog

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Re: EEVblog #763 - Dumpster Plasma TV Bad Cap Repair
« Reply #4 on: July 08, 2015, 12:13:34 pm »
Some of those vertical lines might go away after the tv has displayed some variable content such as a tv show. Plasmas will have image retention, and will retain an image indefinitely if simply left off. However, unlike burn in, the retained image fades away as soon as there is moving content on the screen.

Thanks, I might try running it for a while.
 

Offline Porto

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Re: EEVblog #763 - Dumpster Plasma TV Bad Cap Repair
« Reply #5 on: July 08, 2015, 01:02:04 pm »
I own a Samsung PS50C91H HD-ready 50" plasma for 8 years now and it's still going strong, no problems whatsoever!  :-+

Those things are really heavy and bulky but the image quality is far better than LCD, IMHO.

Will only change it for a big OLED screen! :)

 

Offline tec5c

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Re: EEVblog #763 - Dumpster Plasma TV Bad Cap Repair
« Reply #6 on: July 08, 2015, 03:57:55 pm »
Dave,

When I used to work in TV repairs down south (south of Wollongong), there was a massive problem with the panel in this LG model (give or take some minor variations in models). The customers who had problems with the vertical lines (99% of the time they were pink pinstripe lines) actually had their TV's replaced with a larger and newer technology unit. A 50" model (if I recall correctly the majority of them were 50") was replaced with a 60" 3D LED LCD model.

The old faulty plasmas were left for us to do away with. Depending on the severity of the lines, they were sold for <= $50 each... the buyers weren't phased at all by the lines, granted the ones we sold only had very minor lines, which in some cases only appeared on certain colour backgrounds (a blue background was the worst)

I actually have two of these TV's, both with lines on them. At first, you could at times get rid of the lines by banging the top front of the glass panel, though to any onlookers this would look like you're having a mental breakdown as we used to smack the crap out of the things.

For the most part, there's nothing you can really do to cure the curse of a faulty panel.

Best advice I can give... If you're buying a new TV, get the extended warranty!!

 

Offline EEVblog

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Re: EEVblog #763 - Dumpster Plasma TV Bad Cap Repair
« Reply #7 on: July 08, 2015, 04:03:48 pm »
For the most part, there's nothing you can really do to cure the curse of a faulty panel.

Thanks for that confirmation!
 

Offline ornea

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Re: EEVblog #763 - Dumpster Plasma TV Bad Cap Repair
« Reply #8 on: July 08, 2015, 04:12:10 pm »
Some of those vertical lines might go away after the tv has displayed some variable content such as a tv show. Plasmas will have image retention, and will retain an image indefinitely if simply left off. However, unlike burn in, the retained image fades away as soon as there is moving content on the screen.

Thanks, I might try running it for a while.
So does it look like those lines lined up with the previous fault.

I would be curious to discover your results from the moving content fix.  I purchased several plasma's at auction that looked they had been using at a call centre type place as a couple had bad burn in (image retention) from what looked like a digital clock display in the corner.  Overtime it has definitely faded.
 

Offline peter.mitchell

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Re: EEVblog #763 - Dumpster Plasma TV Bad Cap Repair
« Reply #9 on: July 08, 2015, 04:25:26 pm »
I think something like this my fix the lines.
 

Offline daveykeogh

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Re: EEVblog #763 - Dumpster Plasma TV Bad Cap Repair
« Reply #10 on: July 09, 2015, 12:35:21 am »
I thought I'd post something from a TV repair from a while back. My 37 Inch LG packed in, died with a lovely pink screen. So I investigated, found popped PSU caps, and ordered some replacements from RS. 2 days later I get these caps delivered. Appears the delivery guy ran over them, oooops. #Fail. I should have guessed from the tire marks on the packaging.

 

Online Fungus

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Re: EEVblog #763 - Dumpster Plasma TV Bad Cap Repair
« Reply #11 on: July 09, 2015, 01:44:33 am »
Maybe tape a plastic cup over the smoke detector during the great power-on.... ?

 

Offline Bruce_Davis

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Re: EEVblog #763 - Dumpster Plasma TV Bad Cap Repair
« Reply #12 on: July 09, 2015, 02:47:04 am »
I have struggled with desoldering methods, solder sucker, braid, etc.  I'd like to know what make and model of desoldering tool you used in this video.  Thanks.
 

Offline staze

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Re: EEVblog #763 - Dumpster Plasma TV Bad Cap Repair
« Reply #13 on: July 09, 2015, 02:52:35 am »
Seems these old LG plasma's seem to develop cold joints on the controller boards. You might try the old "pressure" test on various parts of the board and see if it ever goes away.

Seems just reflowing the controller board often fixes it.
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Offline SeanB

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Re: EEVblog #763 - Dumpster Plasma TV Bad Cap Repair
« Reply #14 on: July 09, 2015, 03:35:55 am »
Smoke detector there in the ceiling is an optical type, which uses a chamber with a IR LED and a photodiode, which detects small particulate matter and turns on the alarm. Responds to smoke from a smouldering fire, vape from an Ecig or the venting white stuff from a capacitor dying with great displeasure. Testing is done with a simple test rig, which has a canister of small particle powder and a propellant gas ( normally Propane or Butane, though they used to use R11 so as to make it non flammable) that puts a puff of gas into the chamber, or the simpler test is to press the test button, which moves a reflective plastic flag into the chamber into the light path. the IR transmitter is pulsed with the red LED, so as to have low standby current. Battery low ( or a broken supply lead on these remote powered units ) will result in around 10 minutes of chirping as the on board 1000uF capacitor slowly discharges.

 

Offline Razor512

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Re: EEVblog #763 - Dumpster Plasma TV Bad Cap Repair
« Reply #15 on: July 09, 2015, 06:09:55 am »
For the inside of a capacitor, they seem to have a weird cloth/felt like material with some dark colored chemical on them.

(inside of a capxon capacitor that I took apart) http://imgur.com/a/di5y8

Anyway, does anyone know how what the chemical tastes like :)?
 

Offline Razor512

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Re: EEVblog #763 - Dumpster Plasma TV Bad Cap Repair
« Reply #16 on: July 09, 2015, 08:57:52 am »
Cloud reliance is always horrible as the product or service will only last as long as the company can keep their servers running.

There are also many things that can go wrong or opportunity for them to really screw you over.

For example, suppose a service decides that the customers seem to have a lot of information or a lot of reliance on us so we can raise the price more than we normally would, or begin to charge for previously free functionality, and users will be more likely to accept since they don't want their device to become a paperweight.
 

Offline ColinA

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Re: EEVblog #763 - Dumpster Plasma TV Bad Cap Repair
« Reply #17 on: July 09, 2015, 09:47:00 am »
That smoke detector is probably a photoelectric type which work by scattering light in a chamber and looking for changes on the photo detection sensor. The other type known as ION, is being phased out of the industry and typically were not installed in office type environments. The one shown in your video is a two-wire addressable device by a company know as System Sensor, whom also manufactures and licenses out the technology to several other fire alarm manufactures. It is impossible to tell which manufacture yours is without seeing the fire alarm panel itself or taking down the device (not recommended because they are also supervised).

These are not individually wired back to the system but rather they work on a two-wire 24volt DC addressable data bus. The system installer would program a building location for each device on the bus. One can also attach output relays to these data lines and program them to react when certain logic events happen.

The ION phasing out is a result of the micro controllers now used in these commercial type devices that allow them to be programmed toreact to changing events in the same way the ION detectors did. I can go on and on into more detail but..I cannot be bothered.

I will have to send in a couple different manufactures devices for a mailbag "quick teardown".

 

Offline boffin

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Re: EEVblog #763 - Dumpster Plasma TV Bad Cap Repair
« Reply #18 on: July 10, 2015, 12:47:59 am »
kilobyte = 1024 bytes (JEDEC standard)
kibibyte = 1000 bytes

While JEDEC says that 1024 bytes is a kilobyte, the rest of the world (SI standards an all) say a Kilobyte is 1000 bytes
However, a Kibibyte (kilobinary) is ALWAYS 1024 bytes (not 1000) as defined by the IEC

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Offline mikerj

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Re: EEVblog #763 - Dumpster Plasma TV Bad Cap Repair
« Reply #19 on: July 10, 2015, 02:11:07 am »
the rest of the world (SI standards an all) say a Kilobyte is 1000 bytes

If you read a microcontroller datasheet that stated a device had e.g 16Kbytes SRAM, would you expect 16000 bytes or 16384?
 

Offline Monkeh

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Re: EEVblog #763 - Dumpster Plasma TV Bad Cap Repair
« Reply #20 on: July 10, 2015, 04:21:34 am »
the rest of the world (SI standards an all) say a Kilobyte is 1000 bytes

If you read a microcontroller datasheet that stated a device had e.g 16Kbytes SRAM, would you expect 16000 bytes or 16384?

16384, because K is not an SI prefix.

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Offline Alexei.Polkhanov

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Re: EEVblog #763 - Dumpster Plasma TV Bad Cap Repair
« Reply #21 on: July 10, 2015, 05:39:08 am »
I think something like this my fix the lines.

I fixed two things like this - a conference room wired phone and an LCD panel monitor. Monitor had 2 colour lines and phone had big gap in the middle of the screen. I did not know anything better so I just used heat gun and kept rolling plastic Teflon wheel (not sure where it came from) over the ribbon cables and eventually I got contact.
 

Offline EEVblog

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Re: EEVblog #763 - Dumpster Plasma TV Bad Cap Repair
« Reply #22 on: July 10, 2015, 07:59:04 am »
I'm surprised that you didn't do a rant about losing a days work to Altium's cloud.

a) It is free software that is unreleased and still in beta, problems are to be expected. Ok, not that problem, but you get my drift.
b) It didn't happen to me, so any rant on my part would be irresponsibly based entirely on 2nd hand information.
 

Offline Alexei.Polkhanov

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Re: EEVblog #763 - Dumpster Plasma TV Bad Cap Repair
« Reply #23 on: July 10, 2015, 05:20:04 pm »
These are not always exactly solder joints. Those flex/ribbon cables are sometimes glued with some strange adhesive and then something will need to be pushing against the joint. What I found is that these often fail after being in storage or in a car at -20C or colder temperature. When I lived in Montreal I remember third case - perfectly working LCD display on Panasonic phone died after I carried it home when it was -27or-29C outside. Same thing may happen due to heat. I think it is bad design in general.
Big Apple monitors had that problem too. Co-worker who used to work at Apple store in Montreal ( as a student I assume) also had this theory about why this fault was particularly common in Montreal. Surely enough I got 27 inch apple monitor/PC at work with green line on it.
 

Offline EEVblog

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Re: EEVblog #763 - Dumpster Plasma TV Bad Cap Repair
« Reply #24 on: July 10, 2015, 07:08:53 pm »
There seem to be many TV's around that display colour bars as a result of poor or failed solder joints. I saw a couple of YT videos where poking the controller board or FFC would trigger the problem.  Is there any chance of showing if this TV has the same problem? You could show a detailed view of the cause of the symptoms under magnification.

I think I had a poke around last time it was open and nothing.
Someone who's day job is repairing this model says it's the panel, essentially unrepairable.
 


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