Failure Modes

December 19, 2014 Steve Hawley

Software engineering is funny.  It shares a lot with Computer Science (which honestly, should be called applied mathematics) and it shares some things with other engineering disciplines.  With other engineering disciplines, it shares the need for clear processes for planning projects, managing work, ensuring quality, and handling defects.  I say that it shares the need because not every shop actually does all of these things and there is certainly no one good standard for any of these.  This is an industry problem.

One of the many nice things about being married to a real engineer is that I get to hear a lot about engineering and manufacturing process and one of the things I’ve heard her (and other engineers) talk about is FMEA: Failure Mode and Effects Analysis.  This is process whereby a component can be analyzed for failure and severity or probability of failure can be reduced or eliminated.  This is what I thought of when one of my LCD monitors failed.

We believe that engineers work better when there is more screen real estate available to them.  We also believe that an investment in a good pair of monitors will pay off in terms of other resources saved.  For example, our office supply sales representative asked us in all honesty if we were buying our paper from another source, since we go through very little paper (but a great deal of coffee).  We purchased a fair number of these LCD monitors from a well-known consumer electronics manufacturer.  In a few years, they started failing.  In the past 6 months we have had 4 fail.  Every single monitor failed in exactly the same way: the display went blank and the power light went off.  After a brief pause, the monitor started back up again.  The frequency of failures increase until the monitor fails to work at all.  This to me screams of being a very analog problem, probably power related.  To date, 68% of our monitors failed this way.

I contacted the manufacturer of these monitors to find out if there are replacement parts available, hoping that they would have an FMEA put together with this device that would pick out the likely culprit.  I received worse than no help from the manufacturer, but Elaine will talk in more detail from a support point of view about what they did wrong and how they could’ve done it right.

Since I’m alone in this I chose to ignore the manufacturer's lawyers. 

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By the way – unlike this manufacturer, I’m going to say that if you’re deciding to do this, you should understand the risks. Power supplies in electronic devices can have components that will hold onto a charge long after they’ve been shut off. If you’re uncomfortable doing something like rewiring parts of your house, listen to your discomfort and don’t do this since the charge in a typical power supply cap can give you a nice burn or stop your heart. You know, bad things if you’re not appropriately careful.

I took the monitor apart and looked over the various boards to see if anything obvious was out of kilter and here’s what I found:

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There are three of these capacitors on the board used to drive the CCFL that is used as a backlight to the LCD display.  If you look at the top of the cap, you can see it bulging up.  This is a sign that this part is failing or has failed.  The manufacturer either used the cheapest caps they could find or used underrated parts or both (or heck, even something else).  The point is that all three of the capacitors on this board look like this, and I would expect a large consumer electronics manufacturer to know about this, to admit to it, and to have a well-defined process for managing it, as well as to have fixed the problem in later revisions (and I can tell you that the manufacturing dates indicate on our devices that they likely did nothing of the sort).

Unfortunately, this part isn’t well-marked so I can’t tell you what the capacitance or the rating are, but taking a guess, this particular part probably cost them a few cents in quantity, whereas a higher quality part would have cost roughly 10 cents in quantity.  So someone looked at the design and chose an off-brand manufacturer for the part in order to save 25 cents on the assembly.

The actual cost of this problem was probably far higher in terms of in-warrantee repairs.  Sadly, the most costly loss to this manufacturer is in terms of customer loyalty.  I had a CRT from the same manufacturer that I used for 10 years before replacing it with a smaller footprint, less power-hungry LCD.  That CRT looked every bit as good on the last day as it did on the first day.  The shoddy quality of these LCD devices and the especially poor customer service is such that I will never purchase another product from this manufacturer again and if I have a say in the matter, I will strongly discourage anyone I know or work for from purchasing their products.

By comparison, I have a workstation made by another well-known consumer electronics manufacturer on my desk which I use for my day-to-day work.  The computer shut down without warning.  We reported this to the manufacturer and even though it was out of warrantee, they sent us a replacement motherboard and power supply which arrived the very next day.  When we replaced the board, we noted that the bad motherboard had several capacitors that were bulged up.  The replacement motherboard had caps made by a different manufacturer.

And while a desktop workstation is a different beast than a monitor, the desktop manufacturer demonstrated that the proper way to handle this type of problem is with alacrity not with incompetence.

About the Author

Steve Hawley

Steve was with Atalasoft from 2005 until 2015. He was responsible for the architecture and development of DotImage, and one of the masterminds behind Bacon Day. Steve has over 20 years of experience with companies like Bell Communications Research, Adobe Systems, Newfire, Presto Technologies.

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