LG W2452V 24-Inch Monitor Tear-Down And Repair

Status
Not open for further replies.

iam2thecrowe

Glorious
Moderator
I normally find in Samsung monitors a Samxon capacitor leaking. I swear monitor manufacturers put them in on purpose as a time-bomb capacitor. They fail after about 5 years, long enough that you thought, ok well i had a good run, but not short enough that it is an early failure. Its good to see an article like this, many monitors can be saved this way if you have a little soldering skill.
 

coolkwc

Distinguished
Oct 18, 2007
3
0
18,510
0
Bad cap again...the cheapest yet effective time bomb of all components. Seldom got ppl want to dismantle dead old monitor even they have solder skill, simply because dismantle process before you can access to that tiny component itself already stopped alot of ppl ambitious. So i say this is effective time bomb to kill the device.
 

iam2thecrowe

Glorious
Moderator


I generally have no problem getting anything apart and it only takes a few minutes. But yea i agree with this a little, a HP monitor i recently tried to fix was held together with noting but plastic clips, it was not designed to be taken apart once assembled. The plastic clips often break and they don't go back together 100%.
 

crmaris

Reputable
Dec 4, 2014
4
0
4,510
0
When you want to check which capacitor is preventing a PSU (embedded in a device or a standalone) from starting try heating the ones that look defective with the heating iron. The bad cap once heated will allow the PSU to start and then you will know which one is bad.

If you want a more scientific way then you should get an ESR meter. I have seen many caps that weren't bulged but still were bad (high ESR).
 

coolkwc

Distinguished
Oct 18, 2007
3
0
18,510
0
Basically none of them except those 'audiophile' equipment and PC component hear about our rant over internet/forum about badcap. Consumer product they often use dirt cheap component to maximize their profit. Nowadays especially those Japanese and Korean brand, they just provide design, and left manufacturing process (material decision) to those China maker, so basically Japanese and Korean device = China brand. A good example is Panasonic product never use a single piece of capacitor from its own brand or any other Japanese brand despite the fact that its capacitor is highly reputable. What a shame.
 

Daniel Sauvageau

Reputable
Aug 12, 2014
313
0
4,780
0

To use an ESR meter properly, you have to remove the caps from the circuit first and that's half of the replacement job for a cap you are already suspecting might be bad to start with. I went with the "targets of opportunity" strategy there: I'm already elbows-deep into this thing, might as well replace all potential suspects while I am in there instead of discovering a few more years down the road that another one that I skipped decided to go bad.

If you paid someone $75-100 to repair an LCD, would you risk having to pay for having it repaired again 3-4 years due to skipping a $5 ($1 part + $4 time) opportunistic part replacement?

As far as the caps from my previous repair in this monitor go, I would be really surprised if they went bad without external signs since Panasonic is a far more reputable capacitor brand and the caps I used have much better specs than Samwha's. I repaired a bunch of PSUs using Panasonic FM-series caps and none of them have as far as I know.

If I had an ESR/ESL meter, I might have pulled one out just to see how the three years used FMs compare against fresh ones.


The most difficult part is prying the bezel off to remove the LCD from its enclosure. That part alone took me about an hour the first time since I did not know what sort of snap arrangement was used and there were no broken snaps to give me easier starting points. When I opened it up to do finish the repair this time around, I could have been in and out in about an hour, were it not for the hours spent taking photos for the tear-down.

The repair itself only takes a few minutes once you have access to the PCB when you have a strong suspect before you even open the device and are going straight for it before investigating anything else.
 

cats_Paw

Distinguished
I normally find in Samsung monitors a Samxon capacitor leaking. I swear monitor manufacturers put them in on purpose as a time-bomb capacitor. They fail after about 5 years, long enough that you thought, ok well i had a good run, but not short enough that it is an early failure. Its good to see an article like this, many monitors can be saved this way if you have a little soldering skill.
Em... yeah its called Planned obsolescence, nothing new, just another way most people are getting F'ed and dont know it.
 

razor512

Distinguished
Jun 16, 2007
2,051
7
19,815
15
Many monitors now use lower quality capacitors in order to shorten the lives.

Some will even design the boards around a more difficult repair, for example acer likes to sometimes completely flatten the leads against the PCB before soldering, thus it becomes annoying to desolder.

Here is the repair I did on my acer x191w a while back https://www.youtube.com/watch?v=hLbSbhvTTgY

PS, even on some relatively high quality brands, you will often fine a few cheap capacitors used in order to shorten the life of the panel.

The same also applies to many HDTV's

If the capacitors do not have the leads completely bent, then you are looking at about 40 seconds to a minute to replace each bad capacitor, if they are bent, then it takes much longer because there is always a little bit of solder left over, and you do not want to pull, even if you see a tiny bit as you do not want to damage the solder pads.

While the companies know that some people will do a repair them self, they know that the vast majority of people will not want to do the repair them self. Thus using a design that is is centered around being harder to fix, will prevent them from going to a 3rd party repair service, as the work involved will make the repair costs too high to justify it as compared to just getting a new device.
 

JayTs

Reputable
Mar 16, 2015
1
0
4,510
0
Years ago my Acer monitor died after only 18 months, and I did a repair like this one. I had never opened a flat screen monitor and was amazed at the cheap construction, being held together by wimpy plastic clips and sticky tape. I found failed capacitors and decided to replace all of the caps with high-quality Nichicons. Four years later, the monitor is still working perfectly, running about 16 hours per day.

For anyone who wants to try this type of repair, you need to know the following specs of each capacitor:

1. Capacitance (microfarads or uF). Match or exceed the original.
2. Rated voltage. Match or exceed the original.
3. Diameter and length. You may use a different size if you are sure it will fit.
4. Lead spacing. Measure the distance between the leads from the cap or holes in the PCB.
As explained in the article, capacitors in the power supply should be chosen to handle high ripple current and/or low ESD as necessary.

Once you have the information, it's complicated but not too difficult to find replacements at Mouser, Digi-Key, or other reputable electronic component distributors. Pick a top brand like Panasonic, Nichicon (my two personal favorites). Look for "Aluminum Electrolytic Capacitors - Leaded" or similar.

To replace all of the capacitors in my monitor, I spent about $15.

With good quality capacitors, how long can a monitor last? Who knows?
 

zodiacfml

Distinguished
Oct 2, 2008
1,145
0
19,280
0
This what I hated in electronics. I perfectly working device crippled by these capacitors. That immediately brings me to mobile GPUs that stops working just after your warranty. Grrrr.
 

Daniel Sauvageau

Reputable
Aug 12, 2014
313
0
4,780
0

Well...
1. depending on how the PWM controller is designed, excessive super-sizing could cause control loop stability or transient response issues. The extra energy available in the output caps also means the PWM's output current limit will be less effective at preventing loads from destroying themselves in case of a momentary malfunction or short. Bigger is not always better. I used the super-sized caps I used mainly because I happened to have them in stock and they physically fit on the PCB. Going one or two ratings up rarely hurts but it might not always work, especially with modern devices that require much faster transient response, ex.: Haswell-ready PSUs and VRMs, CPUs, GPUs and SoCs with dynamic core voltage and fast power state changes.
2. that depends on whether the existing caps are used anywhere near their rated voltage. In the LG display here, LG used 25V caps on the 12V rail. I used 16V caps since that is already a 33% margin and should be comfortable enough.
3/4. yup, physical fit is always a make-or-break thing - doesn't matter how good your replacement is if it does not fit.
5. I think you meant ESR, ESL or ESZ. As noted in my tear-down though, reducing ESR may increase ringing since it reduces damping, namely that of resonance between the cap's ESL and other circuit capacitances.

As for how long the LCDs will work with good caps, I think my older LG is about 10 years old now, so my repair extended its life by six or seven years. The CCFLs or the inverter started dying out a few years ago (flickers for a while until it warms up) and I have not looked into that yet. I did have a quick check for any obvious issues but did not find anything. Now that I have an oscilloscope, I could re-open it to at least check voltage rails. If I had a high voltage (3kV) probe, I could also take a look at CCFL voltage, see if the flicker is due to a lamp ignition or inverter output voltage issue. In any case, it seems seven years or so would be a reasonable expectation for CCFL-based LCDs.
 

GKramer

Reputable
Mar 17, 2015
1
0
4,510
0
Daniel, you mentioned that you used a 16v cap for a 12v rail. This is not good. The voltage will exceed 12v many times. You would have to look at it with a digital scope during transients and power on to know how much. Also the 16v number is probably +- 10%. If i was doing the design I would spec in the 25v part for sure. Also do not change the nominal capacitance value. This can cause a instability issues. Slightly lower ESR would likely not cause a problem. The main reason that electrolytic caps fail is do to the ripple current being exceeded. Ripple current is the main factor affecting the life of the cap. I have seen many inexperienced engineer not take ripple current in to account. ( I used to support power supply designers as an applications engineer)
 

iam2thecrowe

Glorious
Moderator


pretty much all motherboards use 16v caps on 12v rails. while i find all these suggestions from technically trained electronics experts interesting, the end result was it worked. I dont go oscilloscoping any capacitor replacements i do and they have all worked fine, so long as you dont use crap quality caps they will last.
 

ddowers

Honorable
Mar 17, 2013
2
0
10,510
0
I have a Samsung tv and the caps overheat on the power supply board. this happened twice. Once I had the board replaced. the second time an old time tech just replaced the overheated caps. Samsung is know for caps failing in all products.
 

Daniel Sauvageau

Reputable
Aug 12, 2014
313
0
4,780
0

16V is the "rated working voltage" - the voltage at which endurance specs are specified at. When you look at capacitors' service life, the operating life is specified for the rated AC ripple peaking at the rated working voltage while at the rated operating temperature. They are the maximum guaranteed ratings, which means the parts are designed with some unspecified margin beyond that to accommodate yields. The only capacitor rating specified as a nominal value with tolerance is capacitance since it has a direct effect on circuit behavior. For the other specs, you just need to meet a minimum value.

As thecrowe said above, all (or practically all) motherboards (and GPUs, PSUs, HDDs, SSDs, etc.) use 16V caps for 12V rails. As far as using a DSO goes, you must have missed the last few slides where I actually did exactly that. While the scaled-down images do not show it clearly, the ringing peaks just over 1V above DC with the part above 500mV lasting less than 200ns (measured on a different screen cap not included in the article because I was already well over the 40 slides guideline/limit without them) and that includes whatever amount of common-noise is introduced by the break-out wires, so we are likely talking less than 13.5V DC+AC peak in this case. (The 12V rail voltage was at 12.57V, in case you wondered where the extra 0.5V came from.)
 

PaxtonFettyl

Reputable
Mar 21, 2015
1
0
4,510
0
Great article! I did something similar on my Dell 24" LCD a while back after it died right after the warranty expired. $700 investment and I just couldn't bear to toss it. Couldn't find the problem, so someone showed how to bypass the built-in power supple with a standard Dell laptop power supply. Works great! Talk about being happy when you know you fixed something. Thanks again for the great article!
 

Globalrebel

Reputable
Apr 6, 2015
1
0
4,510
0
I keep running into a problem with a monitor. It has these lines of dots running across the screen when viewing a image source. The image is there, but the dots are moving and go from top right to bottom left.

I was hoping someone here has dealt with this before. I've tried different connectors and computers, all with the same issue.
 

Daniel Sauvageau

Reputable
Aug 12, 2014
313
0
4,780
0

Well, since you tried different PCs and got the same result, I think it is quite reasonable to conclude the problem is indeed with something in the display. From the description, it sounds like the display controller is out of sync with the data stream. If you have an OSD option to reset or optimize display parameters, you might want to give that a shot.
 
Status
Not open for further replies.

ASK THE COMMUNITY

TRENDING THREADS