It is the fashion these days to show concern with the state of the environment. Rampant use of the Earth's resources have wreaked havoc on the environment. Pollution has become a by-product of manufacturing activities.
To save the environment one of the solutions being implemented is recycling of materials from electronic waste.
The activity of recycling is a process which involves four steps:
Collection of discarded products
Processing: Extracting the materials from the e-waste and sorting the materials into homogeneous types.
Manufacturing: Using the extracted materials in the production of new products.
Purchase: Manufacturers market the products and the consumers purchase the products made from recycled materials.
As we can see manufacturing is the third step in the recycling process. But the bottom line is recycling has been made an adjunct to the manufacturing system and encourages the throw-away attitude among the consumers towards electronic products. The sooner the consumers allow their old appliances to be taken to the recycling plants the easier will it be for them to decide to buy new appliances.
And so we suspect behind all these a strategy of planned obsolescence which may be seen as artificial and intended to shorten the natural lifetime of electronic products.
On the other hand, repair and restoration of electronics products encourages reuse which reduces the need to manufacture new products as replacements. The reduction in production requirements would also reduce pollution that may arise from the manufacturing process.
Product repair also gives the customer the option to delay purchase on new appliances and earn savings.
Most problems that occur in an electromechanical equipment is caused by mechanical rather than electrical defects. And most mechanical defects reveals itself by performing a visual inspection of the mechanical parts. Being able to open the equipment and looking at the parts under the cover is almost halfway to solving the problem.
Take the case of a problem with an Epson C45 printer which I have encountered just recently. The ink cartridge carrier will move to the left side slowly then back to the right side again. As the ink cartridge carrier nears its park position a stripping gear noise is heard and the cartridge carrier appears blocked in completing its travel.
From here on there is no other way to go but to open the unit and inspect what the problem is from inside.
To open the printer I removed one screw located between the label and AC plug terminal at the back of the machine.
To remove the top cover there are four locks that need to be unhooked using a small flat screw driver.
Two of the locks can be found at the back on the lower left and right side of the unit. These locks can be unhooked by pushing through the small rectangular holes.
The other two locks are located at the front and can be accessed through the small rectangular holes located at the bottom corners of the base cabinet. I inserted the flat screwdriver blade through the holes and pried the hooks loose.
After the four locks have been unhooked...
... the top cover can now be removed. Once inside the machine I noticed the ink cartridge carrier pressing against a white lever which must be the object preventing it to reach park position.
I pushed the ink cartridge carrier a little bit back...
... then pushed the lever towards the cartridge...
and it snapped into place, no need to use force.
I plugged the printer to AC outlet, pressed the power button, tested the unit and found it to be working just fine.
It is ironic that something as adverse as the economic recession would provide the stimulus needed to increase demand for repair services. But as statistics from OnForce Services Marketplace Index show repair interventions accounted for 63% of all job orders. New installations for consumer electronics products accounted for only 31% of job orders as reported in the CEPro feature article.
Will repair activities again become a vital part of Customer Service? Surely, the time has come once again for electronic repairers to use this opportunity to maximize the practice of their skills. This is also the chance to cultivate a closer relationship with the customer and encourage them to adopt a mind-set of reuse and having their defective sets repaired instead of throwing away the defective appliances. This will also reduce the volume of e-waste going to the garbage dumps.
This increase in demand for repair services can be seen as the consumers way to minimize spending on new appliances and use the savings for more important items.
Symptom: Black on-screen display(OSD) Cure: Replace diode BZX79-C3V9 on board location 6601. Repair Details: Set used the L9.1A chassis. Picture and sound is good; the only thing obviously wrong was that the OSD was black. When the +3.3V supply going to the microprocessor was measured actual voltage reading was at about +5V. This indicated that the +3.3V supply regulator circuit was defective. The +3.3V supply was restored to its specified voltage output when the BZX79-C3V9 was replaced. Normal color was also restored to the OSD.
'No disc' error message appearing on the front display of the disc player or screen of the TV monitor can often be solved by cleaning the lens of the disc player.
So in my years of working as technical support engineer for a multinational consumer electronics company one of the most frequently asked questions that I have come across from end-users of disc players was how to clean the optical lens.
Always the answer I gave to end-users was to try to clean first the tiny, delicate optical lens of their disc player with a cotton bud before bringing their player to the repair center.
Later, I found out from one service information document that there is a right way of cleaning the optical lens than just brushing its surface with the cotton bud.
OK, according to the service information you have to brush the surface of the lens with the cotton bud lengthwise -- not in circular motion as I myself had been accustomed to do earlier.
For top-loading disc players the optical lens is easy to access. Just lift the tray door and the tiny glass eye looking up at you would be the optical lens. Cleaning the lens would be easy. If the lens looks blurry it might help if you slightly moist the cotton with rubbing alcohol to take away sticky dust or dirt.
For DVD players, you need to take off the top cover of the set. Then remove 2 screws on top of the loader.
After removing the screws the optical lens can now be rubbed with the cotton bud. Always remember to rub lengthwise along the direction of optical pick-up travel.
Symptom: Dead set Cure: Replace R602(220K ohm/0.5W) Repair details:
No voltages measured at collector terminal of horizontal output transistor.
Voltage supply was measured across power supply filter capacitor terminals. Traced the PCB foil from the B+ terminal of the positive side of power supply filter capacitor to 220K ohm resistor(R602). B+ is measured on one side of the resistor R602 but no voltage measured on its other terminal. By using ohmmeter test it is found out that R602 is open-circuited.
TV troubleshooting is about reading the lines on the screen. And in an electronic repairer's work troubles appearing as strange lines on the screen or picture of the TV crop up from time to time. These types of trouble in a CRT TV are most often cause by a problem affecting the scanning or deflection circuits. An example of these TV troubles manifesting as weird lines on the picture was tackled in one of my previous post where a capacitor in the vertical output circuit has decreased in capacitance and caused black lines to flicker across the picture.
The other day as I was flipping through a notebook that I keep where I jot down details of troubleshooting work that I have done I came across a record of a weird lines on the picture problem. Initially the symptom is 'no picture, dark raster'. Increasing the G2 control on the flyback transformer revealed strange lines that break white and zigzag across a blank raster. I was also able to keep a camera shot of the symptom which you can see below.
The lines tell of trouble that lies in the vertical scanning circuit. The lines are symptomatic of excessive vertical scan distortion and fold-over. The TV chassis contains a TDA8172 vertical output IC which does not feel warm when you touch it. This would mean it is not overdriven or overloaded. Voltage measurement on the vertical output IC indicate normal supply voltages. What is obviously abnormal is the voltage on the output pin 5 which measures +5V instead of 0V. Replacing the IC did not provide the cure to the problem.
I decided to scope the input signals to the TDA8172 vertical output IC and discovered that the Vdrive+ signal on pin 17 of the UOC TDA9580 was generating a rectangular wave pulse instead of a sawtooth pulse. Both the Vdrive+ and Vdrive- The UOC was diagnosed to be defective since the sawtooth pulse is supposed to be generated from inside the UOC. A normal picture was restored to the set when the UOC was replaced.
The other week, I had an opportunity once again to browse through the book by Don Matsuda “Electronic Troubleshooting”. This was a book that I was fortunate to have bought - and read - many years ago when I was just starting out on doing electronic repairs professionally.
In the preface to his book Don Matsuda notes that Troubleshooting has its own rules. He notes further that the rules are derived from everyday practice and must be taught from the point of view of practice.
Matsuda starts out the book by mapping out a “game plan” for troubleshooting. The game plan is divided into 5 phases.
Phase 1: The Outside
Starts the troubleshooting approach from outside of the equipment under complain. Identify the symptoms. Make the preliminary inspection of the equipment by operating it and evaluating its performance. Decide whether the trouble is in the equipment or the environment. Interview the user to get a background of the problem from his standpoint. Let him know of any problem you see or foresee be before you start out work on the equipment.
Phase 2: The Gateways Into The Circuits
This is when the troubleshooter goes deeper into the root of the problem and begins an approach into the “gateways into the circuits” . Two of these gateways are the input and output devices. Troubles in electronic equipments can be caused by a malfunctioning input device and symptoms will show up at the output. Or the output device itself is defective. Symptoms can be clues that our four senses can pick up or can be measured by our test instruments. An analysis of the symptom is a step towards finding out the right cure.
Phase 3: Working Your Way In
This involves getting down to the nitty-gritty of instrumentation work. DC voltages have to be measured and bad voltages pinpointed. Trace a signal and identify the stage in its path where it deteriorated.
Phase 4: Nailing Down The Bad Part
This involves locating the defect to the bad part. After pinpointing the defective section a test of its components should reveal the defective part/s.
Phase 5: Cooking
This is what is sometimes called 'burn-in test'. After the bad parts have been replaced the equipment is operated for about 20 minutes or longer depending on the type of fault.
In the book, Matsuda also presents some general strategies in troubleshooting. These are:
Trial and Error; Divide and Conquer. If something does not work, try another solution. Cut up problems into little ones and deal with them one at a time. Follow up on one of your hunches, if it turns out to be wrong, at least you have eliminated it as a possibility. Troubleshooting is not a cut-and-dried process. But keeping the game plan in mind will keep us from getting sidetracked.
Questioning and Thinking Things Over . Question all leads you come across. Poll all possibilities.
Playing the Percentages. Troubleshooters pay special attention to parts or sections in an equipment that have a high failure rate. Parts and sections under great heat, electrical and mechanical stress have the highest failure rate.
The Divide-in-Half Procedure; Divide and Conquer. Mentally divide a circuit in half and test each half. When you identify the bad half divide it again and test. This dividing and testing is repeated until the defective part is located. This is faster than testing the parts one by one. In Steve Litt's 10 Step Universal Troubleshooting Process, the Divide and Conquer procedure is also discussed in detail.
Doing the Easy Things First. “When the odds seem pretty equal – and sometimes when they're not – it is best to do the easiest thing first.... At least you will quickly eliminate a possibility and feel better about taking on the more difficult and time-consuming alternative.”
The book then continues by giving valuable discussions and tips on doing voltage tests: what bad voltages tell, which part must be causing the problem. Also very informative are the sections and chapters on checking transistor circuits, amplifiers, power supplies, high voltage circuits, oscillators, high frequency circuits, TV, linear and digital ICs.
Also, the section discussing the “Nature and Frequency of Parts Failures” gives valuable tips on what parts fail most often. The book reveals that the part that fails most often are transistors. Capacitors come in second place as the part that has the highest failure rate. Resistors come third. And then coils and transformers.
In the last chapter of the book which deals with troubleshooting intermittent tough dog troubles, Matsuda advices to get hold of a piece of discarded electronic equipment that a pro technician has wisely turned down and get ready for some real troubleshooting. “However, it is a challenge and a real learning experience, even if you fail.”
In troubleshooting as in life, failure teaches as much as success.
Coming at the tail-end of 2008 a day before New Year's Eve, a repair technician came to me for help in the repair of a 21-inch TV. There was a problem in the picture of the TV which looks like black horizontal stripes and gaps on the screen. The picture below would describe to you more about the symptom.
And here's another photo:
According to the technician, he has already replaced the TDA8172 vertical output IC. Unfortunately, the trouble still persisted. The vertical output IC is obviously running hot as you can get singed just by touching its heat-sink for just a few seconds.
Based on the symptoms there appears to be non-linearity in the vertical scanning as indicated by the gaps in the picture. A slight fold-over in the top edge of the picture can also be noticed. Since the vertical output IC has already been replaced, I set my sights on the minor components in the vertical deflection circuit.
According to the technician he has already tested the resistors and capacitors located around the vertical output IC using the ohmmeter of an analog multimeter and found no open or changed value resistors. He tested the capacitors' charging and discharging action also using the analog ohmmeter. Digging in to the guts of the TV, I set my sights on the capacitors first as they are known to be the passive components with the highest failure rate - second only to ICs and transistors. Capacitors are better tested with a capacitance meter, not to mention the ESR meter, I skipped testing the capacitors with the ohmmeter. Testing the capacitors around the vertical output with a capacitance meter I found one mylar capacitor whose measured capacitance was way off its rated value. As indicated on its package its value should be 220nF/63V. However, this capacitor only registered 3.2nF on my capacitance meter. Apparently, this capacitor has decreased in capacitance to, approximately, less than 2 percent of its rated value. Getting another capacitor with similar indicated value from my parts bin, I tested it on the capacitance meter to verify the rating before using it to replace the original capacitor which has decreased in capacitance. After installing the new capacitor, the TV set was again turned on. Now we see a clean picture - the black gaps and lines have completely disappeared. So now we have identified the cause of the problem to be the 220nF/63V mylar capacitor located a fraction of an inch to the right of the TDA8172 IC. Tracing the connections on the printed circuit board and a review of the TDA8172 datasheet, it was found that the capacitor was connected to the output pin of the vertical output IC through a 1.5 ohms resistor. The capacitor's other pin is connected to ground pin of the vertical output IC.
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