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Rob Spiegel
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Blogger
Re: Skepticism
Rob Spiegel   12/8/2011 4:03:29 PM
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Hi BEDST,

If you could elaborate on your story and send it to me at rob.spiegel@ubm.com we could include it as a Sherlok Ohms entry. If you chose to do so, please send along a short bio as well.

bdcst
User Rank
Platinum
Re: Skepticism
bdcst   12/5/2011 5:03:29 PM
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Quite often those of us who have the "knowledge" will assume the problem is of a more complex nature than it may be.  But with greater "experience" one can temper the impulse to tear into a problem without first checking on the simple and obvious.  Is it plugged in?  Are all connectors tight?  Is the lens cap off?

The other day I removed a defective device from service and substituted a recently factory repaired unit.  That did not solve the problem.  Good thing I knew there was nothing wrong with anything else external to the device through previous testing as it turned out to be dud.  A second spare worked fine.  Now, I could have decided the problem was elsewhere as the spare had been factory sealed and should have solved the problem!  Sometimes you have to be prepared for the unexpected.

Centrevision
User Rank
Iron
Key to diagnosis
Centrevision   11/21/2011 9:12:23 PM
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"The key to diagnosis,however,is knowledge of how the circuit is supposed to work rather than the availability of elaborate test equipment or a degree in electronics" - Eugene Trundle (Author Servicing TV And Video Equipmemt). From that comes knowing exactky what is wrong with a piece of equipment then its just a short step from having it working again,and the most succesful engineers are,(were?),those who have the aility to quickly track down,to componenet level,the root of the cause. This might sound logic or not but its always the best approach to trouble shooting.I mean,why buy a Mercedes when you dont know how to drive a car?

Rob Spiegel
User Rank
Blogger
Re: Trouble with magnets...
Rob Spiegel   11/21/2011 3:03:11 PM
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Hi Keith,

If you could expand on your story here, we could use it for a Sherlock posting. We try to make sure the postings are at least 300 words. You could get there by explaining some of the hits and misses as you tried before you identified the problem. We're always looking for good stories, and yours looks good.

If you're game, please send it to: rob.spiegel@ubm.com

Keith Harris
User Rank
Iron
Trouble with magnets...
Keith Harris   11/21/2011 2:53:58 PM
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The discussion has called to mind an experience from the late 70's.  A system I was working on had two motor driven components (running just under 1000 rpm) and some electronic subsystems that had to be synchronized to the shaft position of each of them.  One channel was working fine, but the other was triggering erratically.  The shaft position sensor was a bar magnet attached to the rim ofa flywheel and the pickup was a simple coil to generate a pulse when the magnet flew by.  We finally (after hours of looking at connectors and cables) removed the clamp that held the magnet, and discovered that the weak signal was due to a broken magnet.  Based on the appearance of the broken ends the material was probably alnico, which is pretty brittle.  A new magnet solved the problem immediately. 

William K.
User Rank
Platinum
The non magnetized magnet and troubleshooting
William K.   11/19/2011 8:07:18 PM
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I have never come across a failed magnet in an ion trap assembly.

As for getting into troubleshooting, that is something that I do not only for profit, but also for fun. I have written manuals for some of my employers products with the intention that they would save me from needing to visit some plant and repair equipment.

There are two ways to troubleshoot, the first is to check things until you find something that is not right, and the second one is to understand correctly and in detail how something works, and then look for the part that has stopped working correctly. Actually there is a third method of troubleshooting, which is to randomly replace components until the item starts working again. Of course, that method usually will not correct a problem requireing adjustment instead of replacement.

Over the years there have been a few instruments created to assist by substitution of signals. Many of these are called "Channylists", or some other spelling of the same word. The ads are always interesting, but unfortunately many of them offer little more value than a good multimeter, a circuit schematic diagram, and an understanding of how the item works.

There are things made to assist in finding the points of failure, and some of them are indeed quite useful, although many of them still demand that the service person actually understand the process of the device being serviced. So it would appear that a service career may be secure, until the quality of the products being serviced falls to the point where they are not worth fixing.

Charles Murray
User Rank
Blogger
Re: Skepticism
Charles Murray   11/18/2011 6:44:55 PM
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I agree, Rob. Skepticism is the right word. Checking if the magnet is manetized is roughly equivalent to opening your car's hood every morning to see if someone disconnected your battery during the night.

Charles Murray
User Rank
Blogger
Re: Back to the basics
Charles Murray   11/18/2011 6:41:17 PM
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I suppose this has become a cliche, but electronic control has made it more difficult for kids to do the kinds of things that we used to do as kids, Alex. Engines and transmissions have powertrain controllers. Brakes are all ABS. Most components -- even down to the catalytic converter -- converse with engine management system. Then there's the issue of lack of space: On old cars we could lay underneath the car, look up and see the ceiling of the garage. Today, the FWD transaxle obliterates all light under there. The bottom line is that you can still work on your car if you're determined, but it's really hard for kids to know where to start. You have to go to school and take a class to get started, instead of just learning by dumb trial and error, as we did.

Rob Spiegel
User Rank
Blogger
Skepticism
Rob Spiegel   11/18/2011 2:38:28 PM
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It takes a deep amount of skepticism to check of the magnet is magnetized, the same kind of mind that looks both ways before crossing a one-way street. There are many cases in life where the obvious is overlooked.

Ann R. Thryft
User Rank
Blogger
Re: Back to the basics
Ann R. Thryft   11/18/2011 1:16:17 PM
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Not much stuff is repairable or even analyzable anymore--I'll second, or third, that comment. Remember when you could fix not only electrical and mechanical appliances, but also your car? And what about all those budding engineers taking apart the proverbial radio and other old-timey electronics? Good luck with today.

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