One recent morning, I opened my dishwasher expecting to find clean, dry dishes, but instead I saw that the water had not drained.
I removed the top panel to expose the control panel and dishwasher controller. The dishwasher cycles were driven by a timer mechanism with contacts that opened and closed as the timer rotated.
Behind the panel, I also located a full working electrical diagram on which I located the drain pump and the signal wires that drove the pump. On the exact set of contacts that controlled the drain motor, I found the remnants of some type of water bug that had made its way into the timer and decided to reside in the contacts. I decided this unfortunate creature had shorted out the contact with another contact and shorted the motor.
After cleaning the contacts, I emptied the washer basin and pulled out the unit. The drain pump was easy to access, and I pulled off the pump and hooked it up to an auxiliary 120V power source, which still did not turn the pump, so I bought a new pump and installed it. The pump worked, and I reinstalled the unit.
The problem was solved until three days later, when the water again did not drain. I checked the contacts, and there were no bugs, so I pulled the unit and pump out again. This replacement had a removable casing covering the impeller blades. I removed the casing and found a piece of glass that was blocking the blades from turning.
I removed the glass, and the blade moved freely. I also checked the original and found another piece of glass. I then checked the trap on the bottom of the washer and found additional pieces of glass that had passed through the debris filter. I removed these pieces and re-installed the original pump.
It has worked great since this last repair. Evidently, a glass had broken during the wash cycle at some point, and the broken pieces had worked their way through the system, jamming the pump. This was one situation where an obvious problem was not the actual problem.
This entry was submitted by Tim McNulty and edited by Rob Spiegel.
Tim McNulty is an engineering graduate of Penn State University. He works as an engineer in the plastics manufacturing industry specializing in injection molding.
Tell us your experience in solving a knotty engineering problem. Send stories to Rob Spiegel for Sherlock Ohms.
When I used mousetraps it was easy to find the dead mice. But when they crawl into the wall to die after being poisened, it's not so easy. I could always locate the area, but I didn't cut through the wall. So I quit using poisen.
My guess is that it did, until it was thouroughly dessicated by the current passing through it. We had just rented the house, and the cooked rat in the range came with it. Who can account for some people not investigating smells. I have always tried to locate the source of any unusual odors, whether foul or pleasant. In fact, I have often located the failed component on circuit boards by the smell, usually confirmed by either discoloration or deformity caused by the overheating when it failed.
I would think the rat would stink and alert the occupants that something was amiss behind the stove. I once used rodent poisen to get rid of mice. They would eat the poisen, then crawl into the walls to die. We could smell them for a week, but we couldn't get to them.
When I was a young teen, we moved into a rented house, where the electric range did not work properly. On pulling the range out from the wall, we found a rat that had been electrocuted and cooked across the terminals where the 240 VAC feed from the wall socket connected inside the range.
"A good example of what happens with the latter (self-reset) type can be found in most lamp ballasts: we've all seen fluorescent and other discharge-type lamps that SLOOOOOOOOOWLY cycle on and off all by themselves as the ballast and/or lamp gets old and triggers the device during "normal" operation. It's especially annoying in vapor-discharge (mercury or sodium) street lights (even more so if it's the one right beside you bedroom window!). "
Actually in this case it isn't a reseting cutout but a fundamental property of the gas discharge lamp. As the lamp ages the voltage required to maintain the arc discharge rises, eventually (about 20k-25k hours for HPS lamps, about 3/4 that for mercury & metal halide) reaching a level higher than the max running voltage available from the ballast and the arc extinguishes. The discharge tube then cools to a point that the arc can be restruck by the ballest whereupon the lamp's arc tube reheats and the cycle repears. The solution is to relamp the fixture.
I thought that was a huge disappointment when it was cancelled, Ratski. So instead of Texas, Europe gets all the glory, all of the jobs, and all of the resulting technology.
At least your dishes should be super clean as they were being sand blasted as well as washed. The each little chip probably became part of the blasting process. I wonder just how far it would have gone before blowing a hole through the door. Just a thought.
The Superconducting Super Collider (SSC) (also nicknamed the Desertron[1]) was a particle accelerator complex under construction in the vicinity of Waxahachie, Texas that was set to be world's largest and most energetic, surpassing the current record held by the Large Hadron Collider. Its planned ring circumference was 87.1 kilometres (54.1 mi) with an energy of 20 TeV per proton. The project's director was Roy Schwitters, a physicist at the University of Texas at Austin and Harvard University. Dr. Louis Ianniello served as Associate Director.[2] The project was cancelled in 1993 due to budget problems.[3]
Waxahatchie is about 30 miles due south of Dallas, and certainly would have both fire ants and sandy/shifty soil structure. I suspect part of the "budget problems" was failure to see how expensive solving foundation problems would be! Typical government boondoggle IMHO. Thought so at the time, still do!
I'm afraid neither I nor Google can remember or find anything about that! Try Snopes; sounds like an (non)urban legend! There may have been other reasons. Most of Texas has relatively unstable soil formations (that's why few newer houses have basements, because the codes now require floating slab foundations).
Most transformers of this type need to have such a device to get their UL/CSA approvals. The unfortunate part about this particular one was the manufacturer's choice to use one embedded deep within the windings (presumably at the potential hottest spot), and to use a non-self-resetting one. This unit was potted, so I wasn't about to try to rewind it! A good example of what happens with the latter (self-reset) type can be found in most lamp ballasts: we've all seen fluorescent and other discharge-type lamps that SLOOOOOOOOOWLY cycle on and off all by themselves as the ballast and/or lamp gets old and triggers the device during "normal" operation. It's especially annoying in vapor-discharge (mercury or sodium) street lights (even more so if it's the one right beside you bedroom window!). However, I suppose that's better (from a safety standpoint) than a street light that's out and stays that way!
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