Fixing an LCD monitor....

[humble]

I decided to break my no post rule here 1 time with the thought that this might be a very helpful bit of 411 for a few of us at one time or an other. The combination of price pressure on both LCD's and LCD users leaves us with more and more LCD's with marginal part quality and more and more folks pressed for funds when there 18 month old LCD goes on the fritz. Obviously there are a huge number of variables but the most common issue is one where the LCD fires up for a moment and then goes dark. You can cycle it with the power switch and duplicate the condition repeatedly. Normally this is a sure sign of 1 or more failing capacitors. This is actually a fairly simple do it your self fix....

My sons 19" Sceptre X9 had this problem occur during the week so when Friday evening came I decided to go ahead and troubleshoot it. All monitor cases are functionally the same, they have a set of screws and some type of clasp system. You undo the screws and use a plastic knife or wedge to pry the seam open. The guts are pretty simple some have 1 combined board but most have 2 like the Sceptre.




This is actually the "after" picture but it shows the 2 boards and is a pretty typical configuration. If you look at the bottom center right you'll see two upright "baby blue" cylinders, these are the capacitors I replaced. Here is the "inverter board" (PS board) removed prior to replacement.



A little out of focus but the 4 larger "cylinders" in the back are the most likely to fail. The 2 470ufd25V on the left are very problematic for the Sceptre so I decided to swap them 1st (or you can just do them all).

Here is a shot of the 2 capacitors in question replaced...



Here is one of the monitor plugged back in minus the plastic casing for testing...



Total cost was 2 x $1.29+tax and about an hour of time. This is actually a very simple repair with very minimal downside...after all its already broken isn't it? If it's time to upgrade and you've got the bucks then by all means do so....but if you get caught at a bad time or its a good monitor (out of warranty obviously) then go ahead and give this a try

[minke]

nice work,always good to do a bit of soldering to avoid throwing money away.

must add that its probably not a good idea to open your faulty tv and randomly grab capacitors,unless you know what you are doing. I know it,you know it,but we live in the age of the terminally stupid

[daddog]

Wow. Thanks for posting. I just might try that some day should it happen to me. 

[humble]

nice work,always good to do a bit of soldering to avoid throwing money away.

must add that its probably not a good idea to open your faulty tv and randomly grab capacitors,unless you know what you are doing. I know it,you know it,but we live in the age of the terminally stupid

Very very good point that I should have mentioned. There are components that maintain a stored charge (including capacitors). While many are designed to dissipate that charge quickly not all are. If you look at the 1st picture the larger horizontal baby blue/black capacitor is a 300V one. Not enough charge to really hurt you but mishandle it and it will "bite" a bit. Some TV's have ones with 100X+ that voltage, also be very careful around CRT'a since they can implode if they are handled wrong....

[RTHolmes]

nice work

seems strange that after all these years its still bad caps which are the cause of 99% of electronics failures, they seem to have a lifespan of 2+yrs compared to every other components 20+yrs. One of the rotary trim pots on my X52 has gone screwy - I have it mapped to rpms and it drops slowly over time, a quick nudge and its back up to level. classic symptoms of a dying cap and I guess I'll get round to fixing it eventually, unfortunately my weller tcp has fried which will turn it into a £60 repair job

[Ghosth]

Good post Humble, TY sir!  <S>

[MrRiplEy[H]]

Be aware that the LCD screens contain a high voltage component with 20 kilovolts voltage so don't mess with the innards if you're not comfortable with electronics.

[TheZohan]

most monitors that go bad it just a capacitor blown, the computer store i work at we replace them and then use them for in house monitors but its a low cost fix 9 out of 10 times

[humble]

Be aware that the LCD screens contain a high voltage component with 20 kilovolts voltage so don't mess with the innards if you're not comfortable with electronics.

This is a bit misleading and overly broad. As a general rule the only real source of high voltage in any type of display is the flyback transformer...named for the fact that careless contact can result in exactly that. The flyback transformer can hold a charge for up to a week and should be treated with care. It will ALWAYS have red and black leads and a RED wire with insulated cap below is an image from Wiki article...


You can safely discharge the flyback transformer (or a large capacitor) very easily.
http://www.repairfaq.org/sam/captest.htm   

Prudence is always called for anytime your pushing the envelope of your knowledge base but this type of repair exercise is very simple and safe. Stepping up to an LCD TV requires a higher level of caution in carefully identifying the various components but the real points of concern are only 2. Identifying the flyback transformer and any large (and potentially high voltage) capacitors....those should always be discharged prior to handling

[MrRiplEy[H]]

This is a bit misleading and overly broad. As a general rule the only real source of high voltage in any type of display is the flyback transformer...named for the fact that careless contact can result in exactly that. The flyback transformer can hold a charge for up to a week and should be treated with care. It will ALWAYS have red and black leads and a RED wire with insulated cap below is an image from Wiki article...
(Image removed from quote.)

You can safely discharge the flyback transformer (or a large capacitor) very easily.
http://www.repairfaq.org/sam/captest.htm   

Prudence is always called for anytime your pushing the envelope of your knowledge base but this type of repair exercise is very simple and safe. Stepping up to an LCD TV requires a higher level of caution in carefully identifying the various components but the real points of concern are only 2. Identifying the flyback transformer and any large (and potentially high voltage) capacitors....those should always be discharged prior to handling

The problem is that any wannabe DIY electrician may not tell a flyback transformer from a coffeemaker. Very hazardous stuff unless you know exactly what you're doing.

[SPKmes]

Just on LCD screens....when you get a solid line down the screen, could this be attributed to the caps, or is that a bit more of an issue?

[cattb]

Thanks Humble good post and resources to go with
Cattb

[OOZ662]

I run under the issue that I haven't been able to separate myself from my lovely CRTs yet. I'm too scaredy to work on those myself. I'd really like to have a whack at fixing this ~34" TV, but I have no idea what's wrong with it and it's intimidating as hell inside it.

Just on LCD screens....when you get a solid line down the screen, could this be attributed to the caps, or is that a bit more of an issue?

I believe that's an entirely unrelated problem.

[humble]

You need to be much more careful around a TV since the flyback is normally fairly robust. In addition the TV will have other large capacitors that are more likely to carry a charge so you'll wan't to discharge them if you need to handle them. However about 60%+ of the time you can visually tell if a capacitor is bad. The LCD issue can very well be a capacitor (it's the single largest cause of failure in any electronic device). As a general rule you can very safely scout for bad capacitors...if you find one or more that are visibly bad then you've probably (but not always) found the source of the problem. If the board is relatively easy to detach then it's worth attempting a replacement....or armed with the 411 you can go to a local repair shop and flat out ask them...my TV has a bad capacitor, how much will you charge to replace it for me if I bring you board? Whole TV? I've had guys charge me as little as $10 to replace a part on MB if I bring the board in already stripped...I actually had one guy trouble shoot the board find a second problem and fix both for $10.

[noTch]

Hey humble, I went to my local Radio Shack and got some  470uf35v capacitors. Will the "35v" be to much for this application?