Your example of consistancy in components makes so much sense I think it needs to be amplified. Sometimes an equivalent is not equivalent and can lead to faulty assumptions. I think that is also true in terminology. I do not know if that is ever a case in electronics, but in my field different parts of the country call similar things by different names which can lead to confusion when trying to trouble shoot over the phone.
I remember an instance when a customer called me at home about a problem he was having and the conversation quickly turned to jargon and we got the problem solved. When I got off the phone, my wife who had listened to the whole call asked me, "Did he understand what you were saying?" Of course. Why? "Because it did not sound like any English I ever heard before."
Very good diagnostics, and certainly a fault mode that would be quite challenging to predict simply by circuit analysis. So the problem was solved, I hope that there was a design change that came from the dicovery of the problem, and a service note sent to the repair people . That fault mode is not really intuitive. And a quarter of a second is a very short time to hear and evaluate a sound.
So my guess is that there had to be some intuition involved. It is a bit puzzeling about the explanation of how the buzz produced the overload. My guess would have been that it was extending the inrush current time period to where the fuse time delay was exceeded.
kenish--thanks for the reference to the other article. Between these two, I have learned a lot about what relays can do (both desired and undesirable) in a given circuit.
Love that example, Nancy. Being able to leverage your professionals skills with your personal passions has to be extremely rewarding and a great way to keep your credentials fresh. Not to mention, the possibilities for another income stream! Enjoy and keep up the great work.
Interesting point, Naperlou. At the beginning, I would imagine it's a pain to have to follow SAP's system requirements. Yet I can see that would give SAP some control over keeping the system working correctly.
Agree, great troubleshooting and teleservicing! This is very similar to another new article, "Super Mistake Caused Super Voltage" It sounds like the lesson for all of us is to really think through relays in power control applications! Don't regard them as a simple on/off contact device.
Many years ago I was engaged to help a client who had a lot of enthusiasm but little experience and had invested a lot of effort in an amazing invention based around a Tandy TRS80 computer. He was attempting to control the intensity of several low-voltage halogen projector bulbs by using simple circuits originally intended to vary the speed of a mains-voltage electric drill. This too was very temperamental and would sometimes work after a fashion but would eventually blow the fuses very spectacularly, accompanied by loud grunts from the transformers that fed the bulbs. I pointed out that such simple dimmer circuits had no protection against "half-cycling" wherein the AC delivered to the transformer acquired a significant DC component, with obvious results. The "universal motors" in old electric drills don't mind the ragged waveform, nor would a mains-voltage filament lamp. I completely redesigned the circuit to use low-voltage DC with PWM control of the brightness and the problem was solved.
Agree with naperlou. Work with the equipment and understand it. And everything is significant; the 'burp' being a key clue in this story. This reinforces one key troubleshooting theorem I applied first as a technician and then after I got my EE degree: the problem that kicks your butt the hardest usually has the simplest solution, in this case replace the relay.
I liked the fact the entire system was rebuilt and the fact that it wasnt a repeating failure. It was a try and try again to find the failure. Sometimes the textbooks make it sound so simple with the massless ropes and frictionless surfaces. Often it takes a lot of hands on time in the lab to solve a problem.
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