Instructables

Repairing LCD monitor: how NOT to become planned obsolescence victim

FeaturedContest Winner
Picture of Repairing LCD monitor: how NOT to become planned obsolescence victim
Probably anyone, who are interested in technology heard something about "planned obsolescence". There are some descriptions, how to understand this term, but my favourite is the first one popularized. In 1954, engineer Brooks Stevens said that planned obsolescence is "Instilling in the buyer the desire to own something a little newer, a little better, a little sooner than is necessary."
This time we will try to fight against planned malfunctions, by bringing back to life our favourite LCD.
 
Remove these adsRemove these ads by Signing Up

Step 1: LCD tango down

In my case, LCD could not establish connection with graphic card. Monitor resets after catching correct video signal. It has been lasting 15-40min; and then, after one of resets, LCD catches signal and works correctly until video signal is present.

Placing heat-sensitive electrolyte capacitor near elements which are emitting a LOT OF energy by heat is one of the most common method to reduce life time of product. This causes faster loose of capacitance and, in effect, failure of element. And this, exactly, happens to me.

Step 2: Disassembling LCD

Detach all of the cables connected to monitor. Put it on flat surface, display down. Remove all screws and stand. Almost all cases are joined together with clips. Using flat screwdriver you have to separate both pieces of casing. Screwdriver should be as parallel to the edge, as possible. Put it in the bottom of panel, in crevice between parts of case. Slowly push it up, till clips releases.
Use your engineer sixth sense to dismantle EMC shields.
When You get to cables, make photo of all connectors, it will be big help in assembling. When photos are done, You can disconnect all connectors.

When cables were disconnected, i could take out box with PCBs. Locating power supply is easy: look for the board with soldered power socket.
1-40 of 90Next »
othelwaite19 days ago

very useful - thanks! I'm replacing 5 caps on an LG monitor. When you say it's ok if the voltage is higher, how much higher can you go? I have 3 x 16v and 2 x 25v to replace. Could I use all 25v? Again, thanks!

crazypj7 months ago
Just realised my MIL spec doesn't read properly, the design life will generally be longer and under more difficult conditions the minimum hours requirement will usually be far higher than 'consumer specifications. Microsoft has obviously been using the strategy with Windows but obviously consumers didn't believe the 'whistles and bells' were enough to promote purchase of Win 8 so Microsoft has forced consumers to upgrade (or move to different OS - I'm moving)
crazypj10 months ago
There was a problem with electrolytic capacitors in computers and various other hardware from around 2000 until 2007 so it may not have been planned obsolescence?
I had computer motherboard with several 'bulged' caps but only recently decided to replace them (I need a box to run Win 95)
ac-dc crazypj7 months ago
It is not planned obsolescence, that theory can't be justified in any market where there is competition. In a competitive market if one brand fails prematurely then the customer either is an additional cost under warranty fulfillment or buys a different brand which is a loss of a sale.

The actual reason is that lower quality capacitors cost less. The beancounters tell the engineers to use the cheapest parts available that will do the job at least as long as the warranty period for "most" of the units made.

However, keep in mind that many of these capacitors are only rated for a mere 2000 to 4000 hours on their datasheets. If the monitor is on 12 hours a day that is between 6 months and a year of operation. The main reason they last longer than that is they run at a lower temperature than the max rated temp, but it is a guessing game exactly how long they will actually last.

However, ultimately it is the heat that makes them wear out sooner than desired. The power supply is contained in a metal shielding box inside and customer keep wanting small and thin displays so the passive airflow is not conductive to a cool running power supply.

crazypj ac-dc7 months ago
You are kidding yourself if you don't believe there is planned obsolescence
The Auto motive industry has been doing it since the 1950's. Just because there is a competitive market don't you think everyone is doing the same?
Honda have their reputation for reliability because there are less initial faults and have had a 100,000 mile design life since the early 70's (although if you check re-calls they may go back many years and involve millions of vehicles)
On a slightly different track, John Deere tractors were almost bankrupt because they were too reliable, design life of 20+ yrs. They did market research and found a 12 yr design life was acceptable then repairs would start becoming more expensive each year after breakdowns or just 'old age' making a new tractor cost effective.
Electronic components are no different, MIL spec will give minimum hours life requirement, lower spec just means some components fail earlier but generally not poorer quality (if they have to do the same job) The cost is a reflection of this, the testing rather than production is more stringent. I'm led to believe Intel frequently downgrade expensive chips that don't meet design spec but may exceed a lower chip spec (I'm sure AMD, et.al. do the same but I have no information)
drbogg1 year ago
ok that's nice if you can see the damage component (not rocket science) what if there is no visible signs of damage what then ???
ac-dc drbogg7 months ago
Then you can remove them and check their capacitance and ESR with a meter, but odds are (~ 95% of the time) if there is no visible damage then the capacitors aren't the failure point in a monitor. The next step then would be tracing the circuit, seeing whether it is producing the expected output voltages from the power supply. If it is, the fault should lie beyond it on the video board. If it is not, the PSU circuit will need traced from the AC input all the way to the output, first measuring components with power off then if no fault is found, power is applied and checked from point to point again.

To be concise, if someone needs this instructable to fix a capacitor problem, a more advanced repair is probably beyond their skill level and definitely being the scope of what someone could instruct in a reply box on a website unless a person already had specific details about their testing results.
baspazz1 year ago
When working with Capacitors, is there a safe easy way to make sure they are discharged?
ac-dc baspazz7 months ago
The high side (rectified mains current) capacitor will have a bleeder resistor draining it within seconds of unplugging the monitor. The low side switching filtration capacitors don't need a bleeder or drained at all because they are all within about 5V to 12V charge.

This is not the case with some other consumer electronics, but with LCD monitors there's little to be concerned about.
pben baspazz1 year ago
When working on an LCD monitor the best is probably time. Un-plug it and let it set for several hours and then open it up. It is a little more dangerous on a CRT because the picture tube itself can hold a charge for several days. I would stay away from CRTs just beacuse of the high Voltage and they are so bulky. With so many LCD failing because of bad caps you should score a few from any business if you ask around. Be sure to recyle if you can't fix it. The older cold filments in some CRTs has mercury in it. We already have enough mecury in the fish we eat from the coal we burn to power our computers.

The only 100% sure way is to short the two leads of the cap. A needle nose pair of pliers with insulated grips work well but time usually is enough. No cap is ideal and they all have resistance between the plates.
Jords001 pben1 year ago
Isn't using a high ohm resistor better? I thought you could ruin the solder by short circuiting.
pben Jords0011 year ago
You could if you had a huge cap and it hasn't drained. You are not likely to find that in a LCD monitor. The large caps are usually the ones that fail just beacuse filter caps seem to be near the heat producing parts that cause the cap to bulge.
This instructable is excellent but I would recommend that those that are not trained in the gentle art of soldering to go to you local repair shop for TV and computers and obtain from them old PCB's and if you think that you do not need a soldering iron that is all that expensive but those cheapies do not last and can damage the semiconductors it can be life long tool if cared for! My Weller was bought in 1970 and all I had to replace the tips and I used it as part of my tools for over 40 years and it was not all that more expensive than the junk from the Orient they only lasted for six months if I was lucky! The one melted the handle on the first day and the other became red hot in a short while. Use now these old PC boards to practice desoldering and resoldering on this board as if you burnt parts unnecessary then it is too late for tears and use ROSIN cored solder preferably 22gge If some components are stuck with rubber based glue burn this glue with the tip of your soldering iron to burn it off AFTER the connections were desoldered
It is definitely much easier to solder with a good soldering station, but the truth is that the single sided phenolic PCBs used for monitor power supplies can be easily enough soldered with even a low end $5 Radio Shack soldering iron and the default tip that comes with it. Those irons will last for years but the tips themselves will wear down after a few dozen hours of use, or even less if using highly active flux or solder containing it... but certainly far longer than needed to repair dozens of monitors.
jetpower1 year ago
Good work!  This issue is so prevalent that a number of suppliers (including at least one popular Louisiana-based repair shop) package and sell capacitor sets for this exact repair.  I've used a bunch of them to repair "failed" LCD displays! 

Your point about the economics is also spot-on:  The industry's development community has been phasing out 4:3 displays for a number of years.  Reasons given include HD and DVD compatibility, but the bottom line is the Bottom Line:  Pixel-for-pixel, widescreen displays cost less to manufacture than 4:3 displays of equal advertised size, yielding higher profit margins for producers. 

At some point (perhaps when 4:3 becomes truly obsolete), the playing field will again be saturated with a single style, and industry designers will be tasked with developing the next innovative profit accelerator at the expense of value. 

In the meantime, we can make them all wait another 3-5 years (or more) by repairing our good old 4:3 displays, with their 12% more screen real estate for the same "size" screen. 

As your great 'ible shows, we can also continue making our statement against planned obsolescence by repairing our widescreen displays!
jetpower --

"a number of suppliers (including at least one popular Louisiana-based repair shop) package and sell capacitor sets for this exact repair"

-- where? who? help.
ac-dc Rich997 months ago
They do it to make a profit. Their ordering higher quantity gets them a price break then a second monetary advantage when they mark up a kit to sell to you. To recap all the at risk electrolytics in a typical monitor costs only $6 or so to order $4 worth of quality capacitors from Digikey and $2 in USPS postage. Either way you had to know the diameter and height of the capacitors as well as their rating because a shop can't possible preassemble a kit that fits every possible monitor model out there.
Video screens matching the cinema standards (1.85:1/2.38:1) are starting to appear.
Remember we had black bars top/bottom 'letter box' mode with DVDs on 4:3 TVs.
16:9 TVs solved that, so now they release movies in cinema aspect ratios with 'letter box' bars to create demand for wider monitors...
shortw1 year ago
1st)
Electrolyte capacitors used for DC circuits like this one are polarity sensitive. They are marked with an minus.
Installing them backwards will fry the rest of the power supply/ or power board beyond repair.
SO make sure you mark the polarity and make notes before you remove them from the board.!!!

2nd) It is NOT ok to replace capacitors with an capacitor of an different uF value. This could or will put extra stress, voltages and amperage on other components and will or could reduce their life or could destroy them.
However it is ok to use capacitors with an higher voltage ( V ). Usually higher voltage capacitors are also bigger, so make sure that they will have enough room / clearance on the board and after installing the board into the housing so they do not touch anything.
.
I repaired many power supplies just by replacing capacitors. and I am not a electronic expert.  

ac-dc shortw7 months ago
Actually, no on both counts.

1) If installed backwards they will indeed violently vent making a mess you then have to clean up, but it will not fry the rest of the power supply. IF it were a very crude power supply without any overvoltage protection then it could damage the logic ICs on the video board, but otherwise it would just shut down and in either case it should cause no damage to the rest of the PSU.

You don't need to mark them, the PCB almost always has silkscreened polarity markings and even if it doesn't, a simple continuity check between the trace and a known common ground point will tell you which is ground - with their being no negative voltage in a monitor PSU.

2) It is definitely OK to replace capacitors with a different value. They are not used as timing capacitors so it's not a matter of needing a specific uF value. Instead they install one expected to provide at least the minimal level of ripple filtration the rest of the monitor needs, and a lifespan longer than the product warranty period.

In fact, it is a VERY good idea to use both a slightly higher voltage and a higher capacitance value, to use the largest part that will physically fit in the available space. This will cause a slightly higher inrush surge current, but it's fairly irrelevant as the impedance of the rest of the power supply, even all the way out to the electric company transformer, is far more of an impact than a local ESR drop.

Just don't go overboard. For example if the original capacitor is 1200uF, you could get away with using 1000uF, 1500uF, or even 2200uF, but don't try to shoehorn a 4700uF in it's place.

On the other hand, you can also usually get away with using a little bit lower capacitance value if it is an emergency, but then do at least still use a higher voltage so (within the same make and model of capacitor) the ESR does not rise.

I have repaired many monitors' capacitors, doing exactly as described above with zero repeat capacitor failures years later. The last piece of info that helps is pick a top brand with especially low ESR rating, so you can have an expectation the repair will never need to be done again. The cost difference to do a monitor at a time is very small compared to the labor the first time, let alone if the day comes the repair would be needed again because a lower quality capacitor was used for the repair.
veeguy shortw1 year ago
You can usually get away with replacing a capacitor with one of *close* capacitance. Capacitors are not precision devices. A tolerance of 10 to 20 percent is normal and acceptable. Unless the cap is in a critical timing circuit, the close value will most likely work. Look at the picture of the burst caps. Do you think those caps were anywhere near their marked values in the weeks or months leading up to their total failure?

You can *always* replace a cap with the same capacitance with one of a higher voltage, as long as it will physically fit. If instead of looking for a bad cap, you suspect a bad resistor , diode, transistor or other heat producing component, an easy way to get a "snapshot" or a circuit board is to turn the curcuit board upside down, power it up and place a piece of thermal FAX or printer paper on the board. Any hot spots will show up immediately. If you have a row of resistors and one is much hotter than the others (or one is *not* hot when the others are) that's a place to look closer. Same think if a transistor with a heat sink is not heating up, check it out.

I am an industrial electronic technician. I work on everything from handheld gas detectors and handi-talkies to 1000 HP rated Variable frequency drives.
Pwag veeguy1 year ago
I'm going to file this little trick away in my "This is clever enough to be useful some day" box.

Thank you for sharing that.
I agree with veeguy - using a slightly larger value would be fine (normally these caps are just power supply filter caps).
Rich991 year ago
i found three semi-burst capacitors in my magnavox (it did last three years) a year ago. i abandoned the repair when i could not find replacement caps.

where can i find very small volume purchases of these components?

great 'ible, pics and captions... thanks
veeguy Rich999 months ago
Hope you didn't toss your Magnavox flat screen yet. The 37" ones are notorious for the power supply caps going out. You can get all the replacement caps at either Mouser electronics, JDR Microdevices, MCM Electronics, DIGIKEY Electronics and *MANY* more electronics stores. All of these places have web sites, do a Google search. The entire set of caps to fix my Magnavox 37" cost less than $15.- including shipping. The set has been working great for at least 3 years since then.
Great place to find capacitors kit to fix your LCD : http://lcdalternatives.com/Default.aspx

SHUSSBAR---
thanks for the link.
Rich
cube000 (author)  Rich991 year ago
What capacitance do You need?
Rich99 cube0001 year ago
cube000 --

i thought it was three, but only need two... 25 V , 150 uf

i still have all the assembly screws, but it'll be a lot of trial and error to get it back together!

i must have been thinking of a pic i saw describing my exact problem... there's some ible's here on instructables, and a lot of links to other sites.

thanks for responding.
cube000 (author)  Rich991 year ago
Look for 220uF, 25V, low ESR, they will do the job. They are very common.
crazypj10 months ago
I have more trouble un-soldering the damaged ones than fitting new :)
Do internet search of 'bad computer caps' There is a pretty good Wikki on the problem
amnt1 year ago
Thanks for the tutorial, I changed these 3 capacitors! but my surprise when I powered on the monitor, damn! the lcd screen was cracked! :( but at last I could saw that the flashing problem was solved ! hahaha I should be more careful the next time.

Acer Screen AL19A6W
IMG_20130712_193113.jpg
nerd7473 amnt11 months ago
that sounds good until you get to the part where the LCD is cracked
nerd747311 months ago
cool, are you good at diagnosing computers?
As an aside, many (especially older) electrolytic cap problems were caused by something dubbed the "Capacitor Plague" - basically, a tawdry tale of corporate espionage gone slightly wrong, causing the market to be flooded with electrolytic caps that would die after only a short use.

http://en.wikipedia.org/wiki/Capacitor_plague
mickeypop1 year ago
I see talk about planned obsolescence and poor quality caps.   
Having been in electronic design for over 40 years, i know that is usually not exactly true.

One of the most common causes for electronic failures is heat.  Just touch the back of a LCD monitor or TV, feel how warm they get.   This is only the heat that gets thru the plastic, the heat inside is probably  20 - 30 degrees warmer.

The number one weakness common to most LCD monitors is poor air flow. This is largely due to the EFI shielding switching power supplies need to block  RF interference.

The heat builds up in the LCD casing, causing it to cook the caps.  This causes shorting in the caps shutting down the PS.

If you are repairing a monitor it is a good idea to see if you can increase the effective cooling to extend the life or you may just cook the replacement caps too.

Tip;  Keep items away from you monitor.  I see odds and ends set around and on monitors all the time.    Anything that can block convection cooling can also kill the monitor eventually.

There are basically 3 common areas that kill electrolytics most often;
Polarity Reversal, -- they cannot be put in backwards. they will *explode on power up.

Over Voltage, -- If the PS stops regulating or spikes get thru, if the voltage is higher than the cap's rating, if an under voltage cap is used, again *explosion can happen.

Heat, -- (usually most common) Electrolytics are not good with excessive heat, as the heat rises the internal resistance goes down.  This in turn pulls harder on the PS generating still more heat, and the cycle repeats till something gives.  Usually a cocked cap.

* The explosion is not usually a violent action,  just that the cap opening up by sliding the outer shell up, the twisted layers then short together.
You forgot component quality... plenty of horrible capacitor manufacturers out there.
So it's not malice, it's just the drive to keep these things as thin as possible and as cheap as possible and the societal drive to have a "new" thing every year or two that's pushing this.

It's not "Let's build it so it'll fail in a year boys," it's "It only has to last a year or two let's not use the top shelf components."
Actually they buil it according to the BOM, if the BOM says make it as economically as possible then do it. In the industry I work in, we cannot, people would be at worst dead or at least, without electricity.
1-40 of 90Next »