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Replacing Bad Caps in a Good Monitor

Samsung214TBadCaps3Cropped500Wide.jpg

About a month ago, my three-year-old Samsung 214T 21″ LCD monitor started flickering so badly that it could induce a seizure in a lump of granite. It’s been my primary monitor for some time and I love it for several reasons, not the least of which is that it’s a 4:3 and has a built-in pivot on the VESA-compatible stand. So if I want portrait mode I can have it, and all of my machines including the older Dells support it at its 1600X1200 native resolution.

I set the ailing 214T aside and swapped in my downstairs monitor (the older and slower but otherwise similar Samsung 213T) followed by some research on repairs. I had a hunch it was bad electrolytic capacitors. Freaky hardware behavior these days has a high likelihood of being bad electrolytic capacitors, for reasons I explain here. And sure enough, a chap on eBay was selling a caps repair kit specifically for the 214T for $14 shipped. I ordered it, and when it arrived in today’s mail I wasted no time getting to work.

Samsung214TBadCaps1Cropped350Wide.jpgThe “kit” is just a Baggie with six caps and a short length of thin wire solder. If you don’t know soldering you’re going to have some trouble. However, the vendor has a very nice tutorial specific to the similar Samsung 204T/214T units here. It helps that we’re dealing with a power supply board and not a logic board, in that power supply board traces are usually big enough to see. Anybody with a spoonful of bench tech experience won’t have any trouble unsoldering and removing the old caps and getting the new ones soldered in. That took me maybe 10 minutes, granting that I’ve been soldering for almost 50 years and had top-shelf bench tech training at Xerox. No, your real problem will be getting the damned thing apart to where you can remove the PC board to work on it. And the first step is the worst: prying apart the two black plastic halves of the monitor’s case. LCDAlternatives suggests a putty knife in their tutorial, and that’s precisely what it took. And even though I’m very good with disassembly (bruising up a customer’s machine was a serious no-no at Xerox) I scratched up the 214T pretty thoroughly just getting into it. Alas, these units were not designed to be repaired.

Two of the six caps on the power supply board were obviously bad (above left) in that they were domed on top, and one had begun to leak. The others had no visible defects, but that doesn’t guarantee that they hadn’t failed, or wouldn’t fail soon. The kit had six, and I replaced all six.

Total time for the repair was about an hour, including disassembly/reassembly. When I got it plugged back in and powered up, it worked like new, including being a little brighter than it had been shortly before the flickering began. (This is in line with what I’ve read about the effects of bad caps on monitors.) All in all I consider it a big win: Absent the repair, the monitor would have been scrap. I might not have bothered on a smaller or older monitor, but this one I feel is exactly right for what I do, and an hour spent giving it a few more years of service was an hour well-spent indeed.

9 Comments

  1. Tom says:

    If you can get a heavy duty PLASTIC putty knife or one of those plastic spreader tools that are used for car body work they may not be as likely to damage the case when you have to open something like that.

    I have seen video’s of a special plastic tool that makes it look easy, but have never been able to find one. I have thought about making something that looked like it out of Lexan or other strong plastic.

    You are right about things not being made to be repaired anymore. Now that a lot of very good software is Open Source, the hardware is having the hood welded shut — and I am afraid it is going to get worse.

    By the way, it sounds like Solder was really your FIRST programming language too — that is what I have always said!

  2. Submitted to Makezine. 🙂

    -JRS

  3. In anticipation of possible future cap problems with my (currently functional) 213T, I’m going to look for one of those plastic spreader things. “Spreading” is exactly what the task is.

    I began building little radios on pieces of scrap pine board with Fahnestock clips in 1961, based on descriptions in library books, especially Alfred Morgan’s series on electronics for boys. My father had a moose of a soldering iron (more suitable for sheet metal work than electronics) and didn’t want me fooling with it at age 11, but Uncle Louie gave me a Weller soldering gun late that year, and I used it for a long time afterward and rarely burned myself. I no longer use soldering guns because they don’t get into tight spots very well, but for the sorts of things I was doing at 12 or 13 it was ideal.

  4. Tom says:

    Caps. are not the only component failure I have seen in LCD monitors. The Dell E193 that I am using right now had a driver transistor for the HV inverter that drives the CCF back lights fail. It was a Chinese part number and I never found a cross reference. However, a search on E-Bay turned up someone selling the EXACT part in lots of 5 for a buck each. I now have 4 spares!

    I learned to solder at about age 10 with my Father’s old American Beauty iron. I latter got a Wen soldering gun and put my first Heath Kit Receiver (AR-3) together with it. My maternal Grandmother gave me a very nice Ungar Imperial Line soldering iron with a large assortment of tips. THAT was my primary tool until two years ago when I bought a temperature controlled LED display soldering station that I really like. I still have all of the above soldering tools and the AR-3 receiver and use them!

    I HAVE burned myself a few times. In my younger days my reflexes were good enough to catch a soldering iron that slipped off the bench. However, I don’t think I was ever good enough to catch it by the handle.

  5. Tom says:

    Near the beginning of the following video the technician picks up a blue plastic tool and quickly pops open the case of this Dell monitor. I don’t know what it is, but if you can find one of those Jeff, it seems to make it look easy.

    My Dell E193 opened the same way, but without this magical tool it was NOT that easy!

    http://www.youtube.com/watch?v=kdd4dD8UQAw

  6. Lee Hart says:

    The first time I ran into case like this was the original Apple Mac. I opened it by putting a putty knife in the crack, and tapping it on the side. I worked my way around the case this way, widening the gap a little on each pass until it opened.

    Electrolytics have terribly MTBFs, especially when run hot and near their maximum voltage. Look at a data sheet; typical life is around 2000 hours at max temp and voltage!

    It doesn’t help that manufacturers then buy the cheapest no-name ones they can get. 🙁

    I’ve fixed quite a few pieces of dead electronic equipment by replacing the electrolytics. Often there is no visible sign that there is anything wrong with it.

  7. Howard Walker (KI4VEO) says:

    I do hope you remembered to save to old parts bag (I can sorta see the values and voltage ratings.

    Many manufacturers use caps whose voltage ratings are, at best, operating at the razors edge of the buss voltage. Never fear to move up to the next higher rating, i.e. 35V for an original 25V. I would have surmised the 105C rating would be sufficient, unless they were “accidentally” mislabeled. (nod, nod, wink, wink)

    If these were Made in China that explains a lot.

    A friend of mine (NC4L) wrote an article for QST about voltage drops on mislabeled wiring harnesses made from wire produced in China. He showed 2 lengths of AWG 12 and both looked identical from the outside (same insulation OD). Examination of the stranded wire cross section revealed the Chinese AWG 12 was more akin to something UL would rate as AWG 14. Less wire and more insulation in the Chinese wire to maintain the illusion.

    So I make it a rule to always try to identify the manufacturer, buy Made in the USA (when possible) and look for a UL logo. Of course, this will only be good until the Chinese counterfeit the labels for the substandard wire.

  8. Jeff,

    I wish you lived down the street. I have a Kuerig coffe machine that has slowed down to the point that it now takes 3.5 – 4 minutes for the water to trickle through the mechanism. It’s supposed to brew a full cup in 45-50 seconds.

    We’ve descaled it using vinegar and it still has not fixed the slow trickle. I bet you could troubleshoot, and fix this thing. I bet we could even make and sell a video for $24.99 on how to solve this problem .

    1. Look for coffee grounds in whatever holes or tubes the water has to pass through. De-liming solution won’t touch those. You may not be able to get at all of them them, but at least take a look. Grounds can get into the water reservoir occasionally when they escape into the pot itself and the pot is then used to measure and pour water into the reservoir for a new batch. I don’t know that brand (we have a Cuisinart) so I can’t offer much more in terms of specific tips. If you can somehow blow air through the feeder tubes (I’ve done this with a McDonald’s plastic straw) you might try that as well. In truth, these gadgets weren’t meant to be repaired, and if it won’t come around you’re probably better off getting another one.

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