The Case for Working With Your Hands

On Sun, 24 May 2009 19:54:22 -0500, the infamous Ignoramus24299 scrawled the following:

and still end

Back in the day, folks called that the "shotgun approach." Shotgunners were not well received by fellow mechanics or, especially, their own clients.

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I suspect the first one took months to write. It has an academic tone to it, as if it may be a spinoff from some academic paper he wrote in his post-doctoral work. Note the credits to "help" from two people -- probably grad slave...er, students, who researched the references for him.

Crawford has a few other articles floating around; as he said, he does some writing for the money.

Yeah. I suspect the latter.

The _New Atlantis_ piece was published originally in the hard-copy journal.

It will be interesting. Persig wrote pretty well for someone who was mentally disturbed, but his second book, which had something to do with "quality," was as flat as a pancake.

-- Ed Huntress

I spent a year leaning to repair some very complex electronics in the Army. They had concluded that teaching the student how the equipment should work, in exquisite detail, was more effective than an expert- systems fault tree procedure.

This is a set of WW2 submarine technical manuals that illustrate the concept:

Thae Torpedo Data Computer was an amazing accomplishment for its time. The captain tracks the enemy ship and estimates its relative course angle from the length and mast height data in an identification book. The TDC re-created the target's course and speed, refining its estimate from new periscope readings, and continuously programs the torpedo's gyrocompass to intercept. We had similar electromechanical computers for antiaircraft and battleship guns, so the military has long experience teaching recruits how to troubleshoot fast and well.

The Golden Board method of circuit board test is similar. The tester applies the same stimuli to the device under test and a known working board and compares the results. I think the mathematical concept behind it is that a complex system may not reduce to a simpler model, it is its own best description even if its purpose is to do calculations, like the Torpedo Data Computer.

jsw

It depends on the situation. It is very different if you have a couple hundred people standing around iuntil the system is working. I used to try to think of all the possible things that could have happened, and then ask for multiple checks to determine what happened. It had two effects. One was to speed up the troubleshooting. The other was to keep people busy so they did not have time to distract those actually trying to troubleshoot.

The shotgun approach is sometimes the only way to proceed if the failure is very intermittent. If the failure will not repeat in many retests, sometimes removing all the parts that could have caused the problem, is the only way to ensure high reliability.

Dan

No. The original was expanded into the book. Try the large print on the top right ;-)

The problem is that troubleshooting varies a lot. There is a company, Keeper -Tragoe, that teaches troubleshooting. Or at least one method, based on determining what has changed to cause the problem. It is good for some things, but useless in others. Useful if one starts having problems on a production line and someone has changed some procedures. Useless if the cause is a mechanical failure.

Another approach that I learned from a course in Vacuum Tube Technology was to put numbers on things, even if the numbers are a wild guess. Usually one can rule out somethings as the cause this way. It is similar to Operations Research.

As an aside, I took this course back in the early 60's. I thought it would be the last chance to learn about the sorts of tubes used in radios and television, as these were being rapidly replaced by transistors. Wrong!! The course was taught by the chief troubleshooter for Varian. And we covered traveling wave tubes, klystrons, backward wave ocillators, multiple gun oscilloscopes etc. All the students were from places that manufactured these types of tubes, as Watkins Jobnson or Lawence Radiation Lab.

Dan

On Mon, 25 May 2009 08:11:36 -0400, the infamous Ecnerwal scrawled the following:

Hah! Y'know, I saw that little sidebar and read it, but it didn't quite sink in the first time through.

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On Mon, 25 May 2009 01:58:04 -0400, the infamous "Ed Huntress" scrawled the following:

The book _didn't_?

Yeah, or friends off which he bounced his ideas.

I know a few people who do that. ;)

We shall see soon, ah reckon.

Yeah, I see that after rereading that little sidebar.

He's 2-for-2 in my book.

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The book probably took the last three years. Either he recognized that he had a potential book when he wrote the article, or a lot of people said they'd like to see a book about it. That's how those things often go.

I'm of the opinion that a good "trouble shooter" is born not made. It has to do with the way a persons brain works. It's one of those "right or left side of the brain" things. I've been doing that kind of work all my life (I'm 77) and I have seen both kinds of people in service related fields. (mostly electronics). ...lew...

Too many of my friends experience this with their car repairs when done at an auto shop. Techs that are not using good troubleshooting skills will simply try replacing one part that isn't easily tested, declare the problem fixed, and hope it is true.

If the problem recurs the management guy will say to the customer "well, that part needed replacing anyway" and the tech will move on to replace another random part in the system in a "shotgun" approach.

The customer frequently will not challenge this kind of expensive TS as long as it fixes the symptom, eventually. I argue that my friends should challenge such repairs on the basis "I paid for the symptom to be eliminated, not for parts to be replaced", but it too frequently falls on deaf ears.

I agree in that some people do not seem to ever become good. So how your brain works is a factor. But I learned some lessons at various times and became much better at troubleshooting. One was when I was directed to observe some "experts" ( Well factory represenatives ) troubleshoot a computer. The failure only occurred about once in 45 minutes. They would hook up an oscilloscope and run for thirty minutes or so with no failure. Then they would disconnect the oscilloscope and run until the failure occurred. Then they would reconnect the oscilloscope and run. Did this for eight hours and learned nothing.

I learned to always do something so that one gained new knowledge when a failure would occur. Especially important if the failure only occurs every couple of days. I remember one failure that would only occur every six weeks. It was a solid problem when it occurred, Meaning that the diagnostic program would fail every time you ran it. Actually never did fix that problem. It was on a multiply instruction. If you single stepped the computer so you could identify the bad card, it would work correctly and then be good for another six weeks. I took another job about six months after this problem started to occur. Got a call from the new guy when it occurred again. Told him that if he single stepped thru a multiply instruction, that it would disappear. Do not know if he figured out a way to isolate the problem or not.

Dan

I scored a copy of 'Trustee from the Toolroom' by Nevil Shute this weekend for <

10 bucks delivered. I'm fairly thrilled.

Wes

Hey, congrats. That's one for the collection.

-- Ed Huntress

One time a friend of mine got to buy a Case 1450C dozer in which the previous owner dumped a whole bunch of money. It seemed that the thing would stall when the pedals were pushed down and would not move. The dealer ship put in a new torque converter, valve body, and a whole bunch of parts that added up to over 15,000 dollars. The machine was worth

30,000 in good running condition. The previous owner dumped the machine for 15,000 since the factory couldn't fix it. I came by and looked at it for him. The machine was stalling out with the pedal fully depressed. That meant that the brake and the torque converter were working properly, but were coming on at the wrong time. For anyone that doesn't know how the steering pedals work on the 1450C, when you push them half way down it dis-engages the drive to the left or right track. when you push the pedal all the way down it applies the brake to that track. It was obvious that the brake was coming on when it shouldn't and stalling the motor. After pulling off the top cover of the valve body assembly I noticed that the gasket was blown out between one of the galleys and was letting fluid bypass the ports. I put a new 2 dollar gasket on the machine and it ran like a deer. :)

Anyone can keep replacing parts until the thing runs, its replacing only the bad part to get the thing back on line.

John

Excellent book, one of many. My paperback cost me a quarter 5+years ago. Gerry :-)} London, Canada

Snort! It didn't take me long to figure out that the "factory reps" more often than not didn't have a clue. What they did have was neat/expensive test equipment, lots of spare parts, overnight (or faster) shipping arrangements, manuals and schematics not available to us and access/phone numbers to people that I couldn't get.

Sometimes they would listen to me after beating their heads into the wall and it got a bit soft. Sometimes not...

There were some sharp ones around (factory reps), but they usually didn't last/stay for long.

Amazon shipped it today via USPS. I'll slap on a new label when it comes in and point it your way.

Wes

Well, I sure hope you're going to read it first. d8-)

-- Ed Huntress