LCD Monitor issues/Repair - Page 1
Forum section: electronics / repair

author: Nevakonaza
author_rank: Contributor
timestamp: January 06, 2013, 06:17:18 pm
content: Hey guys,Hopefully i can get some help,Now im new to electronics but its something ive always been intrested in and want to learn.I have a LCD monitor here,22" belinea 0. display,Its been in the loft/Attic for a while,In its original box & wrappings all sealed up..it was fully working when it went up and now its not.When i first switched it on..the green light,and the screen were flashing very quick..then i turned it off and tried again...nothing,No lights...no sighn of life.So i open up the back to take a look inside (for bulging caps etc) they "Visually" look fine,I have replaced the T2 5Amp fuse on the PSU board...plugged it in and tried again,The green light flashes and so does the screen very fast..but that's it.Not sure whats happened to it to be honest,It was going to a friend as he has a 14" monitor lol.Would you say its a cap problem?...or a problem with the board that recieves the signal from the pc?The PSU board has 12 caps.5x 470mf 35v5x470 mf 25v2x 1000 mf 16vAppreciate any help here,please excuse the noob-ness.

author: marshallh
author_rank: Unknown
timestamp: January 06, 2013, 06:59:04 pm
content: Possible causes that come to mind1. Bad CCFL tube (unlikely as they will last 5-8 years in consumer elec.)2. Open/shorted HV transformer windings (usually thermal stress/shock related)3. Controller board failure (unlikely)4. Power supply problem (more likely)Take clear, well lit and focused pictures of each pcb. If you're lucky the voltages coming off the (usually separate) power supply pcb may be labeled. You're right that caps are usually the first thing to go.Heat is an alum. electrolytic cap's worst enemy. If the attic temperatures were sustained over 90 degrees F for more than just a little while, it's plausible some/all of the dielectric fluid has dried out. Caps don't have to be completely gone and busted to cause problems... I would replace them all.Panasonic FC or FM series low-ESR caps for replacements.

author: Nevakonaza
author_rank: Contributor
timestamp: January 06, 2013, 07:17:47 pm
content: Quote from: marshallh on January 06, 2013, 06:59:04 pmThanks for replying.You mention - 2. Open/shorted HV transformer windings (usually thermal stress/shock related)In the summer it does get rather hot in the loft,and during the winter very cold!Would you really say its worth buying all those caps,then using the time to replace them...and potentially still not fix the issue?

author: Skimask
author_rank: Super Contributor
timestamp: January 06, 2013, 08:29:11 pm
content: Yep, I'd try it.A 10pk of 470mf 35v caps and a pk of 1000mf 16v...Got any good "junk-tronics" laying around you can scavange parts from?Generally speaking, you can almost always go higher in voltage ratings, like 99+% of the time.Cap values...a bit of a different story. I've never had a problem going with higher values (never lower), maybe 50% higher. So you could most likely go with 680 for the 470's and probably 1500 for the 1000's. But you kinda gotta make sure they're all matched up...e.g. if the cap's you're pulling are in "pairs", replace them as matching "pairs".

author: Nevakonaza
author_rank: Contributor
timestamp: January 06, 2013, 09:02:07 pm
content: Not got any junk electronics that i can salvage from,But looking around at local stores then sell the caps i need individually and i can buy each of what i need separately.Does these look "Okay"..there's the 470mf 35V,I don't think they're a branded make or anything,But i just want to get the monitor working for a cheap as possible...i mean it might still not work after replacing the caps. :/Ive not linked to the caps or site ,don't want to break any forum rules or anything.With all 12 caps id need,comes to just under £5.5x 470mf 35v5x470 mf 25v2x 1000 mf 16v

author: M. András
author_rank: Super Contributor
timestamp: January 06, 2013, 09:09:40 pm
content: if the caps wont solve the problem you can take them out and reuse for something else dont buy twice

author: Nevakonaza
author_rank: Contributor
timestamp: January 06, 2013, 10:28:28 pm
content: Would you say those i posted above would be suitable?Says in their description they are suitable for TVs...but not sure if this is just a selling gimmick.

author: marshallh
author_rank: Unknown
timestamp: January 06, 2013, 10:50:38 pm
content: If they don't say Low-ESR... they aren't... those look to be the cheapest available.They will work but suffer the same fate eventually. They are used for filtering switch mode supply outputs, which is why it's important for long term longevity you get proper caps and not just any old caps.It's up to you, it will probably work with those for at least a while.

author: justanothercanuck
author_rank: Frequent Contributor
timestamp: January 06, 2013, 10:54:15 pm
content: Not every monitor uses just 1000 and 470uf caps... I'm in the middle of fixing 4 LCD's and here's my shopping list:2x 220uf 25v4x 220uf 35v4x 470uf 25v2x 1000uf 10v6x 1000uf 16vQuote from: marshallh on January 06, 2013, 10:50:38 pmI had that issue today... Ideally, you would want a cap that's low ESR and high temp, but I could only find either-or. Eventually I settled on low ESR, because if they fail again, I can just replace them again in a year or so when they fail.

author: Nevakonaza
author_rank: Contributor
timestamp: January 07, 2013, 02:02:12 am
content: Thanks for your help guys,Sourced some "United Chemi-Con" caps on Ebay,and they work out cheaper than if i were to get those i posted earlier above...they're Low impedance/Low ESR ,Long life 105c rating.

author: 6502nop
author_rank: Regular Contributor
timestamp: January 07, 2013, 03:29:27 am
content: I'd be a bit leery about eBay caps. There are many counterfeits out there. I highly recommend going right to the source, either DigiKey or Mouser (not sure what else you've got in the UK).United Chemi-Con (UCC) makes some very good LESR caps, and is one of the top four - those being UCC, Nichicon, Panasonic, and Rubycon. My go-to for caps, especially those for switch-mode power supplies (SMPSs) is the Panasonic "FR" series, which have taken over from the FC/FMs. To give you an idea, here's what I found at Mouser:Nichicon PW 470uF/35V (#647-UPW1V471MPD) = $0.68 ea,Panasonic FR 470uF/35V (#667-EEU-FR1V471) = $0.39 ea.Nichicon PW 470uF/25V (#647-UPW1E471MPD) = $0.48 ea.Panasonic FR 470uF/25V (#667-EEU-FR1E471) = $0.35 ea.Nichicon PW 1000uF/16V (#647-UPW1C102MPD) = $0.70 ea.Panasonic FR 1000uF/16V (#667-EEU-FR1C102) = $0.39 ea.As you can see, the Pannys are a bit cheaper, with the same or better specs. If you're looking elsewhere, the Panasonic and Nichicon part numbers are the same as Mouser's, with the first three-digit section taken off (647=Nichi, 667=Panny).Now, about those caps - what they do, and why they're in there...In a linear power supply, the main caps are used to filter out the 50/60Hz frequencies and store the charge. It'll be 100/120Hz if it's after a bridge rectifier. Still, not too high a frequency, so a regular General Purpose (GP) cap can be used. I really like the Nichicon "VZ" series for this.In a "switcher", or SMPS, the frequency is stepped up quite a bit, typically running about 100KHz. To filter this effectively, the internal impedance of the cap, mostly defined by the Equivalent Series Resistance (ESR), needs to be very low. This means the cap can now handle much higher frequencies, but that's not all. These SMPSs also crank up the current, too. So, your poor cap now has to filter high frequenciesand"ripple" currents. And if you're wondering, the "SM" in SMPS could also stand for "Sado-Masochist", because the caps are, by design, sitting right next to components that tend to get very hot. If you're keeping score, that's a "Low ESR, high ripple current, 105C rated cap".After some trial-and-error, a few Japanese companies came out with types that fit the bill. About ten minutes later, the Chinese companies came out with their "crapacitors". The difference is night and day. In fact, there are some brands of "craps" that are considered to be "Replace-on-Sight", such as Fuhjyu (or "F-Us") or G-Luxons. If you want your SMPS to last, stick with:Nichicon PJ, PW, HD, HN, or HZ series.Panasonic FC, FM, or FR series.Rubycon YXG, MBZ (?) series. <-- rare as hen's teeth to find!UCC/NCC LXY, LXZ series.If all you do is simple low frequency (<30-50KHz) breadboarding or linear power supplies, then the Nichicon VZ are about the best bang (if you hook 'em up backwards) for the buck in GP caps and the Panny FRs for SMPSs. Note that some PC motherboards require even better caps than an FR on their Vreg sections, so be sure to double-check specs when recapping a mobo.If you haven't yet ordered these, then please post the link to the ones you want to buy, as well as the actual brand and series of caps that are on the PSU, so that we can take a look and see if they're the correct series for the job.nopIt's pronounced "Nee-chee-kohn", by the way.

author: mariush
author_rank: Super Contributor
timestamp: January 07, 2013, 03:41:51 am
content: Nichicon HM, HN and HZ are discontinued. Use HD and HE, they're not quite super low esr but still low esr. Certainly much lower esr than some noname/chinese capacitors.Panasonic FM and FR are low esr. FC is tehnically still low esr, and it was considered one years ago but by today's standards is not that great. On eBay you may find Panasonic FL or FJ... don't recommend buying them, Panasonic only sells to high volume buyers and FL/FJ aren't available at official distributors so who knows where the ebay people source them from.United Chemi Con has also KY and KZE series that are good capacitors, low esr, high ripple, quality capacitors. Avoid KZG and KZJ series from them, they're known in the repair guys "circle" for going bad with no reason after some time, probably manufacturing flaw in these series.Rubycon has some series with low impedance, low esr .. ZL* series.. ZLK , ZLG ... see chart here:http://www.rubycon.co.jp/en/catalog/e_SERIES-CHART.htmlThe ones towards the top are best.Try to order from official distributors digikey.com , newark.com/farnell.com (same company) , rs-online.com , mouser.com

author: Nevakonaza
author_rank: Contributor
timestamp: January 07, 2013, 04:02:08 am
content: Thanks so much for your help guys,really helpfull.These are the caps i was going to order.35V 470uF (need 5x)http://www.ebay.co.uk/itm/14081643582725V 470uF (need 5x)http://www.ebay.co.uk/itm/12070178597116V 1000uF (need 2x)http://www.ebay.co.uk/itm/16V-1000uF-105-C-Panasonic-8mm-radial-Capacitor-X-2-/120673487086?pt=UK_BOI_Electrical_Components_Supplies_ET&hash=item1c18b348eeAs for distributors,i cant seem to find many in the UK...their either overpriced or have a minimum amount you have to spend on the order,OR have no 25v 470uf in stock....Ebay gives me better options.I also have another question,discharging caps...is this necessary for the caps im replacing? ,especially been on a Power supply?..im new to all this,But we got to learn somehow eh?

author: M. András
author_rank: Super Contributor
timestamp: January 07, 2013, 09:05:00 am
content: 25ZLJ470M10X12.5 farnell has 1600 units of them its a 25v 470uf pretty high ripple cap. i doubt farnell has minimum order limit even in the uk and not that expensive of course if you buy 1k at the same time the price will drop to the third of the 1 unit price idiotic pricing on their end. for ebay if you willing to gamble and buy again caps when they die again its up to you. as i said dont buy twice

author: Nevakonaza
author_rank: Contributor
timestamp: January 07, 2013, 11:11:03 am
content: Quote from: M. András on January 07, 2013, 09:05:00 amJust checked out Farnel prices,For all the caps i need but using RubyCon...the total comes to more than twice the price of the Ebay NichiconsMy ebay selection £4.95 inc deliveryFarnel £13.44 (Minimum Order Quantity: 5 caps of each value)big difference,and quite a lot of money to pay for not even knowing if the monitor will still work after changing the caps.im slightly confused by your post...are you saying those 25V 470uF i have linked too are no good?Thanks guys!

author: G7PSK
author_rank: Super Contributor
timestamp: January 07, 2013, 12:05:58 pm
content: You could go for the cheaper ones and if that makes the unit work upgrade the caps. and keep the cheap ones for a less demanding job.

author: dave_birdi
author_rank: Contributor
timestamp: January 07, 2013, 12:15:35 pm
content: Quote from: Nevakonaza on January 06, 2013, 06:17:18 pmCould you upload a picture of what you saw?

author: justanothercanuck
author_rank: Frequent Contributor
timestamp: January 07, 2013, 12:55:40 pm
content: Quote from: Nevakonaza on January 07, 2013, 04:02:08 amIt's always good practise to discharge all your caps, but in my experience the caps in LCD monitors are normally already discharged because of how they fail. But getting shocked by a cap hurts, so I'd always recommend discharging them.

author: Nevakonaza
author_rank: Contributor
timestamp: January 07, 2013, 01:09:57 pm
content: Heres a video of what happens,Sorry for the quality it was shot on a phone camera. :/ ...its all i have.You probably cant see it,But at the same time as the green light is flashing,so is the screen panel slightly...i don't think the camera picks it up though.

author: justanothercanuck
author_rank: Frequent Contributor
timestamp: January 07, 2013, 01:12:46 pm
content: Yeah, that sure looks like power caps to me.

author: Nevakonaza
author_rank: Contributor
timestamp: January 07, 2013, 03:31:38 pm
content: QuoteHow would i go about discharging them?...ive never done anything like this before,Would you say something like this is a too big/risky job for a noob like me?I appreciate honestly,I wont be offended or anything.

author: mariush
author_rank: Super Contributor
timestamp: January 07, 2013, 03:57:05 pm
content: Could be the starter cap faulty based on how it behaves... it's a small capacitor around the transformer... probably the one at 0:54 in the video. Generally, it's something like 10uF/33uF/47uF xxV around the transformer. Those don't usually swallow because they're so small but they go bad as they're near heat source.If Farnell forces you to a minimum of 5, you can use 35v rated capacitors instead of 25v rated ones if you have same capacity but different voltages on board.These will work for both 25v and 35v locationshttp://uk.farnell.com/panasonic/eeufr1v471/capacitor-radial-35v-470uf/dp/1800666(check diameter)http://uk.farnell.com/panasonic/eeufr1v471l/capacitor-radial-35v-470uf/dp/1907239(8x20 check height)http://uk.farnell.com/panasonic/eeufm1v471/capacitor-radial-470uf-35v/dp/1219475(10x20 check height)these will work instead of the 25v oneshttp://uk.farnell.com/panasonic/eeufr1e471/capacitor-radial-25v-470uf/dp/1800650http://uk.farnell.com/panasonic/eeufr1e471l/capacitor-radial-25v-470uf/dp/1907237(8x20 check height)http://uk.farnell.com/panasonic/eeufm1e471l/capacitor-radial-470uf-25v/dp/1219470(8x20 check height)http://uk.farnell.com/united-chemi-con/elxy250ell471mj20s/capacitor-470uf-25v-radial/dp/2113034(10x20 check height)http://uk.farnell.com/rubycon/25zlk470m8x20/capacitor-radial-25v-470uf/dp/18312868x20for 1000uF 16v, you can generally use 1200uF instead if you can't find 1000uF cheaply, the design is not that sensitive at the capacity value at that point. You can also use 25v instead of 16v, just be careful at diameters and height.ex these will workhttp://uk.farnell.com/panasonic/eeufr1c102l/capacitor-radial-16v-1000uf/dp/1800638http://uk.farnell.com/panasonic/eeufr1c102/capacitor-radial-16v-1000uf/dp/1800637http://uk.farnell.com/panasonic/eeufr1e102/capacitor-radial-25v-1000uf/dp/1907238http://uk.farnell.com/panasonic/eeufr1e102l/capacitor-radial-25v-1000uf/dp/1800654http://uk.farnell.com/rubycon/16yxf1000mefc10x20/capacitor-1000uf-16v-radial/dp/1144617http://uk.farnell.com/panasonic/eeufm1c102/capacitor-radial-1000uf-16v/dp/1219463See, it's not that much expensive compared to eBay but farnell may charge you some shipping fees.

author: M. András
author_rank: Super Contributor
timestamp: January 07, 2013, 10:25:27 pm
content: Quote from: Nevakonaza on January 07, 2013, 11:11:03 amif those ebay unkown origin caps die like the originals from the monitor then you lost your money, from farnell i seriously doubt you will get any fake stuffs. i haven an old 7+years old viewsonic monitor, dead/faulty caps replaced them with some yageo and god knows what brand none of them was high enough ripple or even low esr type to work flawlessly it still produces the same fault but only 1/10 starts not every start, thats why i say dont buy twice, i admit i didnt brother to check the links only that it was from ebay and its a gamble you can get fake, factory defect units or even ones which was pulled from boards at the recycling plants somewhere in china or india

author: 6502nop
author_rank: Regular Contributor
timestamp: January 08, 2013, 06:19:33 am
content: QuoteGuess it pays to keep up with these things, huh?QuoteI thought they fixed them? The problem batches had date codes of, IIRC, 2004 (maybe as late as 2006?).Nev, the video posted is really blurry and moving, making it hard to see who's made the caps (and series) so we can better match them up. If you can post any close-up pics of the caps, or just jot down the markings, that'd help.About the only cap you need to worry about discharging is that big mother with the tie strap around the middle. This filters the incoming mains (240V?) before it gets sent to the switcher primary. Since this is 50/100Hz, it can be any GP cap, and it's rare this goes bad (good news!). This cap also handles about 340V after rectifying (bad news!). So, if you discharge only one cap, it'll be that one. A simple way of doing this is to bridge the leads of the cap with a resistor. The higher the value of resistor, the lower the power rating can be (and the longer it takes to discharge). I just check with a meter to see if it needs to be discharged, and if it does, I have a few various high-wattage resistors handy. As canuck mentioned, I've also never had to discharge a modern monitor PSU - they seem to have built-in "bleeder" resistors/circuitry. I'd still measure that big cap, though...The eBay seller has posted pics of what appear to be UCC KZE series caps (good!). If that is, in fact, what he/she actually sends you, then go ahead and take the gamble. The last link shows what appear to be the newer Panasonic FR series by the color and font, but no mention of series is given. If this seller seems legit, go for it, but don't be surprised if what you open up is some other brand or Chinese counterfeit.Now, while I agree about the PSU problem being cap related, mariush does bring up a very good point. If you're not sure of what to replace, or how to test, then the best bet is to replace any/everything that would cause this problem. Since you're not blowing fuses, the primary can be declared good. Since the light comes on and gives an attempt to power-up, then we can assume the 5Vsb is good, too. Most monitors now incorporate a "soft start" feature in the main control chip to keep the initial surge of current to a non-fuse-blowing level when it has to charge up the output caps. To do this it uses - you guessed it - a capacitor. In your video, it should be the little guy to the left of the main filter cap with the strap,right next to the big heatsink! Since that little cap only adds about another 25 or 30 cents to the order, may as well swap it out while you're in there.Since I see that some of those caps are butting against each other, it is imperative that you double-check the diameter, lead spacing, and height of the new caps to match the old ones. I accidentally jotted down the wrong diameter for some mobo caps and had to re-order. It was a difference of 8mm vs. 10mm. I still have no idea how I wrote down "10" when the calipers read "8".Another common failure is the inverter (backlight driver) caps/transformer(s). This is where the HV for the CCFLs is generated. Again, if you're not sure, just replace the caps you find in there. Since all this is on the same PSU board, you may as well do it while you're there. The transformers/CCFLs would be the next thing I'd check if recapping doesn't work. For now, we'll just take it one step at a time.Lastly, a real noob wouldstillbe trying to get this thing open. You've done that, taken the holiday movie, and have a relatively good understanding of what needs to be done. Just take good notes, make sure the caps are the right way 'round, check for soldering errors, and as your fellow countryman once advised: "Don't Panic!"nop

author: Nevakonaza
author_rank: Contributor
timestamp: January 08, 2013, 05:02:09 pm
content: Never been on a forum with so helpful people,Thanks a lot guys really appreciate it.@mariush,Thanks...Those caps are a lot cheaper than the ones i choose on Farnel,Il take a look at what that small cap is near the transformer and add that to the list ....I wonder why they don't give any shipping prices though,Might contact their live support and ask how much this will be.As for that huge "big mother" cap,I don't have anything to discharge it with (this is whats worrying me about the whole project)...Ive done soldering etc at collage so i can solder,But that was with detailed diagrams on how to build stuff...im new to all this going it alone, and all i have is a (borrowed) soldering gun & Solder wire lol.

author: mariush
author_rank: Super Contributor
timestamp: January 08, 2013, 05:19:53 pm
content: Quote from: 6502nop on January 08, 2013, 06:19:33 amNichicon HM (and possibly HN as well but I'm not sure right now) were faulty up until the end of 2004, when they discovered the flaw and fixed them. They were overfilling them with electrolytic causing premature failures. Nichicon HM with date codes 2005 and newer are OK.UCC/NCC, as far as I'm aware, never admitted that their KZG and KZJ were bad, but they silently discontinued them a while ago.You won't find them in the catalogue:http://www.chemi-con.co.jp/e/catalog/pdf/al-e/al-all-e1001m-120801.pdfYou won't find them in discontinued series:http://www.chemi-con.co.jp/e/catalog/pdf/al-e/al-sepa-e/001-guide/al-standardization-e-120701.pdf.. and they're not oem only as they were on digikey about 6-8 months ago maybe... I don't remember exactly.KZG was sort of top of the line when it comes to ultra low esr/impedance, about as good as Nichicon HZ.And because they were mostly used on the VRM on motherboards, they eventually go bad, maybe from heat cycles... there are cases recorded when KZG series capacitors bloated just by having a motherboard in storage for half a year.PS. I keep saying UCC/NCC because a lot of people are saying Nippon Chemi Con to show that they're "Japanese" but the company that makes electrolytics is "United Chemi Con" so... not that it matters that much.

author: M. András
author_rank: Super Contributor
timestamp: January 08, 2013, 09:02:41 pm
content: http://uk.farnell.com/jsp/bespoke/bespoke7.jsp?bespokepage=farnell/en_UK/support/webhelp/deliverytimesandcosts.jspthey say clearly the shipping charges3 pounds

author: dr_p
author_rank: Frequent Contributor
timestamp: January 08, 2013, 09:18:06 pm
content: I had the same problem on a 19" LCD. It turns that a week before final failure there was a blown SMD fuse that someone repaired by drowning it in a solder blob.Then something (the original reason for the blown fuse) on the HV CCFL board went short-circuitthen the PSU would cut off, try again in 1 second and so on. That was causing the flashing power LED.I've read around, people are generally pointing to the HV transformers.I didn't get around to trying to fix it, mostly because the owned annoys me and I'll be doing him a favor, so...

author: mariush
author_rank: Super Contributor
timestamp: January 08, 2013, 09:36:11 pm
content: I forgot to mention in my previous posts that often, the problem for lcd monitors not starting is just a loose wire on one of the cfl lamps. They're usually in pair, and usually both pairs (or whatever pairs you have) are controlled by a single IC.If the wire from a lamp gets loose, the controller keeps trying to light the lamps for a few seconds (depends how it's configured) then triggers fault and the power supply shuts down. If you get the datasheet from the IC you can usually replace the (usually smd) capacitor that's combined with a resistor to create the timeout value with a much larger capacitor and then the power supply will try for 10-20 seconds to light up the lamps and you can see which side is more dark than the other and proceed.But in this case, you'd see a flash on screen and sometimes even the manufacturer logo before it turns off and sometimes restarts, not like in the video where it seems it resets itself very fast.