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Showing posts with label boards. Show all posts
Showing posts with label boards. Show all posts

Sunday, November 6, 2011

Why electric units fail?

There are number of possibilities.
Testing,inspecting and troubleshooting is the only way to confirm what caused the unit to fail.
When a unit faults, it will always give a Symptom, now, the Symptom is what the user is experiencing, and a symptom, is exactly that, a Symptom. Now, just like with people, there can be many, many, things that can bring about the same set of symptoms, say like fever, a fever can have any number of "Causes" from the Flu, to say Bubonic Plague... Well, just like our bodies, electronics are similar, insomuch, as The "Symptom", is only that, and the real "Cause" of the problem, is often far removed from the actual thing we experience with a failure. I have been doing this since the Valve or Tube days, and while the circuits have gotten more complex, the principles still remain the same. and as I have found, just about every problem even though they often present the exact same Symptoms, have completely differing "Causes". and repair strategies.  People often ask me "Why" one day a seemingly, working unit, spontaneously fails. Well really the answer is simple, it is the electricity going through the unit, this electricity, is constantly "Stressing" all components, some more than others, every time you turn the unit ON, there is a phenomenon called "Inrush Current" now this "Inrush Current" can be Very High, and over time this, occurrence eventually destroys some components, as well all this all components get hot, it is a function, of it working. The Thermal stresses, caused by heating up & cooling down, will eventually destroy even the hardiest components, & some are more susceptible than others. Nearly all circuitry is interconnected to each other, and a problem in one area, will often cause a problem, seemingly unrelated in another. You see the thing that fixes most units, is Experience, gained from years of actually "Doing it" and as one goes on, patterns develop that will get you into the "Area" of the problem, where you then have to test Component, check the Voltages to find the problem. Sometimes even with years of experience, it is still UN-fixable, and the cause unknown, for many reasons, often unavailability of parts. cost of parts In the "Old" days we were trained to design a Machine to last for at least 20 years usage, and design in a 40 year parts retention. However that simply is not practicable any more, and now production runs are done, with perhaps a 5 year life cycle, and without any regard for "Spares" at all. As, the manufacturer doesn't want you to "Repair" the unit, they want you to "Replace" it or "Upgrade" to a newer model. As they see it, and maybe rightfully so, that when a unit is "Fixed" it is still a "Fixed" unit. Meaning, that once, a unit has failed, once, it has stressed, almost every other component, as well, and it WILL, in all likelihood, fail again, in the not too distant future. Not all, "Fixes" will have this result but enough to warrant the "Approach" taken, right or wrong. "They" are trying to give you the "Best Deal" which to "Their" mind, is a "New" unblemished, UN-repaired, unit. (As an aside here often the units go "Faulty" before they even leave the factory, and are "Fixed" and put back into service, waste not want not?) So all in all, it is indeed a great achievement, with all things considered, that the units we all love and use so much, even go, and keep on going, at all. Now some "Repairers" use what we call a "Shotgun" approach, and that is to replace each and every component in the area they perceive the fault is. This often results in a seeming, "Fix". However IF the actual "Cause" is NOT found, then the "Symptom" will simply re-appear, as soon as those components that were replaced, break down. The proper approach, is to find the actual "Fault" and repair that, then repair any "Damage" done, that was "Caused" by said "Fault" this is the ONLY way, an effective, and long lasting repair can be made.
This details will help you to understand the problem and let you decide,whether to get the unit repaired or go for new unit.



How to troubleshoot voltage issues?

You connect your over or refrigerator or tv power cord to electric power outlet.But this units will not work.You assume that problem is with tv or oven or with refrigerator.
But the actual issue is voltage at your place.
The voltage needs to be tested.
Before we can attempt to repair anything at all, there is one thing that one MUST do before anything else is done. Now that is, the making sure that the Power Supply,of the unit, no matter what it is, has the correct Voltages, coming into it, and more importantly, coming OUT of it. This is absolutely imperative, as, IF these Voltages are NOT correct then NOTHING will work, properly at all. So we must measure these voltages with a Volt Meter. or a Multimeter set to DC Volts. ( Always use a good quality meter, as if your meter is bad, so are your readings, and we can need to read to within, +/- 0.1 Volts). All Voltage measurements are made with reference to ground. Meaning we clip, our Black, Minus, Lead onto the Earth, or Chassis, or Negative (-) "Rail" of the Power Supply. Now with the Red lead, we can now, measure these Voltages. Now sometimes, the Voltage of each Output is annotated,or written, onto the PCB, that will indicate the Voltage of that output. However most usually they are NOT, so in this case we MUST have a manual to tell us. Now this manual is called a "Service Manual" or sometimes a "Repair Manual" This manual, is absolutely vital, so much so, that it can be near impossible, to do without it. To Order ANY "Bits" you need the parts, "Part Number" a Number that "Identifies" it to the Factory, so we/they know what it exactly is. Without that number you simply cannot get the correct parts. Also too, apart from having "Troubleshooting" step through's, it also has our Voltages. When we measure these Voltages they are 100% EXACT, so IF the Voltage you measure, except for a few rare exceptions, the "Rail" that is NOT at the correct voltage is the one, that the "Fault/Cause" is "ON". Therefore we can now work outwards from the Power Supply, looking for the cause of that problem. Now if the Voltage is Lower than specified, we are invariably looking for a "Short", something has "Faulted" and is "Dragging" the Power Rail down to earth. possibly a Capacitor, or Diode, or an IC. Now if the "Rail" is "Higher" than the specified Voltage then the fault we are looking for is usually some sort of "Open Circuit" possibly a Diode, or Resistor, that has changed it's "Value", due to heat or stress. Now knowing this, and knowing that, the Power Supply is the FIRST & ONLY place to start you troubleshooting and repair from. You now have a MUCH better chance of a "Fix". 


This above mentioned details will help you to troubleshoot voltage issues.




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