My church’s data projector stopped working, and since I was known to be an electronics engineer, I was asked to take a look at it to see if it could be fixed. The symptoms were very simple. You applied power and nothing happened -- no power, no LED, nothing.
I searched the manual and troubleshooting guide which told me nothing more than to turn the power on. The remainder of the troubleshooting section assumed the power was on and the unit was responding to its remote or buttons.
I decided to dismantle the unit. The assembly appeared to be designed neither for ease of assembly or disassembly. It seemed to be assembled by very cheap labor, where the cost of assembly was not a significant portion of the overall cost to manufacture the projector. After I removed the covers, the main board, the rear interface panel, and the cooling fan assembly, I was able to remove and check the input filter -- It was OK.
The next suspect was the power supply. With great difficulty, I managed to remove it and partially dismantle it to the point where I could unplug the input power cable and check to see if there was power. There was none. Obviously, there was a break between the filter and the power supply. Then I noticed, mounted to the bottom of the case, a suspicious-looking device with the power leads running through it. I removed it and discovered that it was an undocumented, resettable overload switch that was accessible through a small hole in the base of the case. When I pressed it, it gave a reassuring click and power became available at the power supply connector.
I decided to take a chance that this was the only problem and reassembled the unit. It worked perfectly again. I have to wonder how many units have been thrown out needlessly and how many customers have been charged exorbitant fees for repairs when the fix required the serviceman to simply poke a pin through a hole in the base to reset the switch.
This entry was submitted by Bill Washington and edited by Rob Spiegel.
Bill Washington has worked as an electronics design engineer in telecommunications and general electronics for more than 20 years. Prior to that, he spent more than 10 years in electronic equipment installation, repair, and refurbishment.
Tell us your experience in solving a knotty engineering problem. Send stories to Rob Spiegel for Sherlock Ohms.
So was the resettable overload switch added to the build after the original design was sent to the manufacturing line to assemble some prototypes for testing? I suspect this is an "after the deadline" modification that was added either after review of initial tests, after a few failures in the field, or just as possibly, added for distribution in the US in order to comply with U.S. electronic device certification. If it was not part of the original design, it is possible that this little feature was added after the original manual was sent to the translators to generate the English version...
It sounds like the documentation was poor to begin with. I am also wondering how many other features for servicing are generally hidden from the public. I have noticed on other products that have a reset function available through a small hole that is placed unobtrusively somewhere that it is not always documented. An older computer comes to mind where the CD drive would not eject. A phone tech support guy directed me to the fix. I agree that an after-design add on for all the reasons you stated is very possible for this scenario - how hard would it have been to add it to the accompanying documentation as an insert and institute a documentation revision? Poor planning at its best...that church is certainly blessed to have a savvy engineer!
You could be right. Something added after everything was set to go to market. However, a little sheet of paper could have been added in the back of the manuel to help out savvy tech-EEz like this gentlemen.
Sometimes I wonder in cases like this if the company isn't banking a little bit on service dollars. So they don't want it to be fixed by someone at home. kind of annoying, really. I'm glad that the service line you called gave you the little hint to help you out. But that doesn't always happen.
I agree, jmiller. In all of the comments here, everyone seems to be scratching their heads. You have to wonder if this is just a matter of carelessness or intent.
The differnece between an engineer and a non-engineer is the phrase "I decided to disassemble the unit." That is a big step the others would not take. Good job in doing what needed done.
I think the difference is the fact that the engineer could put it back together. Also interesting that taking something apart often is exactly what voids the warranty. Still neat to see it get put back together and working.
Nancy, don't get me started about poor technical documentation. I must admit I'm a stereotypical engineer and don't like documenting but it is a necessary evil. Getting my masters in systems engineering really trained me in creating good documents as well as taught me how to proof them. Creating good documentation is very difficult, time consuming and really hard to get a lot of engineers to do. Believe it or not most of my clients do a really really poor job and most of the time it isn't even on the list of important things to do. So the fact that the reset switch wasn't documented isn't a surprise. In some cases companies do this intentionally so the customer is required to return the product so they can be charged a fee. On the other hand, companies don't find it important enough to have documents reviewed and/or the reviewers don't take the necessary time to ensure the appropriate information is in the specific document.
I agree with your assessment about documentation gsmith120. It pervades all aspects of industry. One of the secrets to my success as a test engineer was that I documented my code (lots of comments). Whenever I needed to troubleshoot or upgrade a system I had built three years prior - I could very quickly determine how to accomplish the task. Documentation is very painful up front but it sure can solve a lot of potential problems in the future!
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