Temperature Protection Fuse

If you are repairing Hair Dryer, Iron and other type of set that have heating element in it then chances is high you could see the temperature protection fuse in it. The common specification that you can see from the fuse (printed on its body) are the Volt, Ampere and the Celsius. If you want to locate the parts from any electronics shop make sure you get the exact spec. Assuming if you really can’t locate any of the original spec then there are two important things that you need to know. You need to find the replacement that have lesser ampere and lower Celsius. For the volt, it will always be standard. If your country is using 240 volt then the fuse rating would be 250volt.

Please do not get a replacement fuse that have higher ampere and Celsius because if the set have problem and the fuse did not break, the whole set will catch fire or it will melt the casing! As usual, before replace the fuse, one must always check the connection, wiring, insulation and etc because there must be a reason why the fuse blow in the first place. After replace the fuse, fully test the set before returning to customer.

SOURDE : JESTINE YONG

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Phobia In Voltage Testing

I’d heard some stories about technicians that have phohia problem especially in voltage testing. The reason why they had this problem was because they may had been accidentally shorted some of the testing points in the electronic circuits. The spark generated by the big filter cap or the electronic circuit section totally blown that had caused them not bold enough to perform voltage testing again. For your information, voltage testing can solve lots of electronic problems fast and if you did not use this method of troubleshooting, you may have a hard time in locating fault.

Now in order for you to gain back the confident of voltage testing, i suggest that you play around with electronic project kits first that use low DC voltage. Once you are good in pinpointing fault in DC circuit then only you move on to AC circuit. Your other option would be to get someone that you know to help you in this area. If you need to pay then just pay him to learn about the voltage testing. Once you are good in voltage testing there is no limit of electronic circuits that you can test thus finding fault faster than any other method
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Testing Components Onboard and Offboard

I used to get this question either from my students or from ERG members about could all electronic components be tested onboard? I told them that as a beginner one must start to test the components off board so that they could understand the components characteristic. With this, they would know if a components is bad, leaky or good. Once they are good in testing electronic components off board, they then can slowly learn to test components on board.

I told them that NOT all components can be test on board. Components like coil, thermister, bridge rectifier, fuse, e-caps, transistor (with collector and emitter removed) can be test on board. Other components like the zener diode, diode, varistor, FET, non polar capacitor, resistors have to be test off board for accuracy reading.

Basic Care for the Battery of Cellphone

Do not charge your battery when your cellphone is on or mobile phone is open it is better to off your phone. So that it may not damage the circuit of your mobile and may not short the life of it's used

The first or new battery of your mobile should be fully discharge adequate electricity and then use

In charging the battery, be sure that your mobile phone only are on the ac outlet and no other equipment such as tv were shared on the same outlet.Because on the otherhand your mobile affects the picture of tv

Do not expose your battery in too hot or too cold areas. It may affect the life of the battery

Monitor the charge time of your battery. So the battery will not overheat and even your cellphone

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Do We Really Need The Exact Same Schematic Diagram

Assuming if you come across a circuit that have few components burnt and you have no idea what the components are, the fastest solution is to look for the schematic diagram-am i right? The problem is sometimes we can’t get the exact schematic perhaps the equipment is still new in the market. The question is “Do we really need the exact same schematic diagram in order to find out the burnt components value?” The answer is not really. Why? because sometimes different brand of equipment could have the same design as yours so you could refer to that schematic instead of the exact schematic. In this post I’m assuming that you can’t get the original schematic diagram and trying to find an alternative way to find a solution to your problem.

Lets take this for example. Common power supply design utilize the UC3842 PWM IC and by comparing few of this design you will eventually roughly know what are the components in the power supply circuit. If the IC pin 1 connected to a 1 k ohm resistor you will notice that other model of equipment that use the same IC may have the same value of resistor (1k) connected to pin 1! I hope you get the idea.

Sometimes we just have to spend a little bit of time trying to find the “nearest” circuit design to your equipment model so that at least you will have some idea of what are the components that need to be used for replacement

Another Way To Find Technical Data For Semiconductor

experience before of not be able to get the specification for the semiconductor that you need? You have search from all the search engines like Google, Yahoo, MSN and etc and still not be able to find the data that you need. For your information not all semiconductor data would be indexed by search engine. That means if the search engine did not index the data of a particular semiconductor part number then you will not be able to retrieved the info even though you have keyed in the exact part number in the search engine.

Don’t give up hope yet as there is another way to find the semiconductor datasheet that you need. First identify the manufacturer of the semiconductor. For example LM IC is belong to National, HA for Hitachi, TDA for SG Thompon/Philips, MC for Motorola, LA for Sanyo and etc. Once you have identified the manufacturer then go into manufacturer website and type in the part number in the search box. With this method, chances would be high for you to get the semiconductor data that you need

How Do You Test UPS Battery

Okay, how do you test UPS battery? UPS stand for Uninterruptible Power Supply and this equipment use the seal lead acid battery type. If you check the voltage of the battery with a normal multimeter, then i guess it is not accurate because a bad battery may also show a good voltage. The battery will fail under load test! If you really need to accurately test the battery you need a battery tester that is design to test such battery like the one in the photo. For a good battery the pointer will kick up and stay there and you could feel the heat underneath the meter (perhaps there are big resistors to act as a load). You can’t test it for long as it can become very hot. At least with this test you are now know that the battery is good.

If the battery is weak (but multimeter showing good voltage) the pointer will flick and then gradually coming down. In fact this type of meter is design to test on the automobile battery and can be used to check on seal lead acid battery too. Do you have other way to accurately test a seal lead acid battery

Different Between A Sales And A Technical Person

Obviously there are lots of differences between a sales person and a technical person. I will only touch on one once point which is that the sales person usually do not like to stay long in a place. How do i know that? Well i have a friend who is doing sales all his life and my question to him was “Why do you want to be a sales person instead involve in technical area? Of course he gave me few answers but one answer that he gave was that he does not like to sit down in a repair bench for a long time! He told me that it was boring to sit whole day trying to troubleshoot electronic fault! Now this is one thing that differentiate us from the sales person, we as electronic repairer in fact prefer to sit down quietly (doesn’t mind if it take a whole day) to troubleshoot the fault till we could find the answer.

Sometimes we did not even realize that it had been more than 2 hours troubleshooting the fault and we did not find it boring in fact we find it very interesting because deep in our heart was that we need to settle the problem and find out what components that had cause failure to the equipment. When the problem solved, the satisfaction is beyond description and looking forward to repair more electronic problems. The more we repair the equipment the better we are! These are the things that the sales person would not understand

Recognition Of Different Types Of ICs

Here is a photo of many different type of ICs. Each IC has it own name/package so whenever someone mention SOT23 package you will know how the IC look like. You may print this photo out for reference purposes

RF Bypass

Have you ever wander why there are two capacitors (an electrolytic and a non polar cap) in the same output line of a power supply? Electrolytic capacitors have thin aluminium film rolled inside the can. This kind of construction makes it inductive like a coil. The inductive reactance is negligible at power line frequencies, but it does become significant at radio frequencies.

Such capacitors therefore, cannot bypass high frequencies to ground because of their inductive reactance. In order to solve the problem a non polar cap like polyester, ceramic and etc of smaller value in parallel with the electrolytic capacitor is use to bypass the high frequencies

Are You Familiar With This Bridge Circuit

believe you have come across such circuit (bridge rectifier circuit and how it works) especially when you study any basic electronic course or reading any theory books on electronics. It is good to understand the circuit/diagram but in the actual repair one have to know about how to accurately test the circuit or component be it off board or on board. A guy who is good in electronic theory could reason with you about how all the current flows in the circuit and etc but when comes to testing the bridge rectifier they are stuck.

So if you really wants to be good in electronic repair make yourself good in testing electronic components and of course understanding how the circuit works would be an added advantage for you

Using Capacitor Value Other Than The Original Value

I got question like ” If my original capacitor value is …. then i can i use this value……? Well the answer can be yes and no and it all depends on what circuit your are working on it. If the capacitor is located at the secondary filter side say 680uf 16 volt and yes you can use a higher value like 1000 uf 25 or even 35 volt. However if the capacitor is part of the oscillator that produce a typical waveform say .22 uf then a replacement of .33uf may affect the overall output waveform and may also cause totally no output at all. In other words sensitive circuit that involve frequency the best is to use back the original value or even the same type of capacitor. That means if the cap is a metallized polyester cap then get back the same type and not putting mylar cap or ceramic cap. If the cap is in the filter section you can replace with a higher cap value but not lower cap value.

If you have no knowledge of what type of circuit you are working on then you can always “Try out” and test the result. Record every thing down from the test so that you can always refer back to the test result just in case in the future you come across a situation where you can’t get the original capacitor value

Induction Heating Cooker

One of my friend gave me an Induction Heating Cooker and he told me that the electronic board inside was rusted. For those of you who has never seen the internal section of the induction heating cooker before then here is the chance to see it in the photos below

AC Power Cord Problem

A member of mine email me about his problem with the RCA television where there was sparking at the AC input area. He could not locate the fault and asked for my advice. As usual i get him to check for any loose connection and bad components at that AC input area but he could not find any bad part. After couple of days later i got his email and this is what he had written:

“The problem with the RCA tv was that the line cord was breaking down under load.Just imagine that and the multimeter was showing good continuity.”

Well in electronic repair line anything can happen, normally only electronic components that breakdown when under load but this time it was the AC POWER CORD! I did not suspect that either but I’m glad that he had solved the problem. So please take note , in future if you come across any suspected section have problem and yet you could not locate the faulty component, try to replace one by one component as there might be a high chances that the components in the suspected location could have breakdown when under full operating voltage

What Is Oscillators

Quite often we hear the word oscillators in the repair world. You heard other tech said “Is it oscillating”. You have heard of the horizontal and vertical oscillator IC in the Monitor. From datasheet you found an oscillator circuit inside the power IC like the PWM UC3842 and etc. So what exactly is the oscillator? An oscillator is an electronic circuit that converts dc to ac. That means the oscillator circuit or oscillator in the IC get the supply dc voltage and output an ac sinewave. They can be used to generate almost any waveshape ( sinusoidal and non sinusoidal) at almost any frequency.

If you compare the oscillator IC and the amplifier IC, you will know that amplifier IC are used to increase the strength (power) of a signal fed into it. This is different from Oscillator IC where this circuit is producing it owns signal (waveform)! That’s why when you look at the spec of the Power IC in SMPS, you would not see an input waveform pin but could only see the output pin and this output pin (pulse and high frequency) is the waveform produced by the internal oscillator circuitry to switch the Power Mosfet

Components Breakdown When Under Full Load

Sometimes even if we have the best tester, we may miss out in finding out the bad component-why? because those components only breakdown when full voltage was applied on it. That means, your meter or tester may check it to be good but failed when the equipment was “on”. Semiconductors are prone to this kind of failures like diodes and transistors. So how are we going to solve this kind of problem? First you have to make sure that the problem was at the location and not in other section. For example if the main fuse always blow upon switched “On” and all of the components in the power and the secondary filter section checked to be okay then the only choice you have is to replace one by one the semiconductor in the primary section area. It could be a bridge rectifier or the big filter capacitor that had caused the fuse to blow when under full load.

However components breakdown when under full load was not that frequent. Sometimes whenever a badge of electronic equipment that uses the components that have problem, the whole badge would be affected. There was one model of dell 15″ LCD Monitor that have intermittent power blink problem. Sometimes the Monitor could work for whole day but the next day the power would blinks. When you switched of the power and “On” it again, sometimes the power may come back. The problem was in the fet 2n7000 located in the power section. All tester used tested good on this component yet it failed when under full load. The hardest thing to diagnose was that this component gave intermittent problem.

Since I’m very sure the power section is the main caused, i replaced one by one the semiconductors and eventually found this bad components. I had came across quite a number of it and i believe many similar model will be coming in for repair that have this intermittent power blink problem

Buying LCR Meter or Digital Capacitance Meter

If you want to test coils and capacitors i would suggest you to buy both the meters. Why? because the LCR ( Inductance, Capacitance and Resistance) range have some limitation especially on the C and the R range. Both ranges are not wide enough to test the resistor and capacitor values. A stand alone Digital capacitor meter have a wider range and could test all kind of capacitor values. This is also same for the digital meter. I mainly use LCR meter to test inductor value only. However if you could get LCR meter that can test full ranges of C and the R then it is not necessary to buy the digital capacitance meter

Which Meter is Better-Analog or Digital Multimeter

Well, it depends on own preference. I’ve seen tech that was wholly dependent only on analog (some old technicians) and also tech that was on digital meter. As for me i use both. From experience, different electronic components need different meter to test it out and we can’t use only one meter to test all of the electronic components. You may use it but the result that you will get might be wrong. Now the truth is besides analog and digital meter, my repair bench is also equipped with ESR, flyback/coil tester, inductance meter (LCR meter), scope, high voltage probe, CRT rejuvenator, Smart tweezers, regulated power supply and many more. Why i need so many type of meters? Because different components need different meter to test it out. You can’t use a multimeter to test the condition of the CRT tube!

Not only that, with more meters it could help you to speed up your repair time without all the guessing game. If the components are bad the meter will tell you and so on. It is not a waste to invest in the meters because you will use it all the time assuming you have decided to join the repair trade. If you scan through ebay i’m very sure you will notice many test meters for sale and some of it is in the high end type but with the price of normal meter. If you are a believer that one meter could solve all of the electronic problems i suggest that you open up your mind to try out some other meters. Give yourself a chance to let other meters capabilities to help you out in your repair work and save you plenty of time. Happy troubleshooting and repairing

Capacitor Replacement

I came across lots of LCD Monitor problems with bulged electrolytic capacitors. The rating of the capacitor temperature usually were 105 celcius. The problem with these capacitor is that they are not from a good quality grade thus it easily become bulge whenever the environment is very hot especially due to the metal casing covering the whole LCD Monitor power supply/inverter board.


It is not easy to get the 105 celcius electrolytic capacitor from local electronic suppliers thus the only option i have is to replace with a good grade (branded) 85 celcius e-cap. I had changed many of the e-cap in the LCD Monitor and so far not even one unit came back for warranty repair.

Comment from Amin

hi thks for the two interviews n that encourages to go forward n gives us new blood
in past years there many Contec tv having problem with start n vertical the faulty were the caps in the smps n in the vertical section ,ur problem with the bad quality make me remember the old days .when i was changing the caps i also changed the place i.e adding
a long wire n placing the caps away from heat, thus there were no start n vertical problems again

About Five Color Band Resistor

I came across many times in Monitor repair that the five band resistor had gone opened circuit. For your information, five band resistor value is more accurate than the four band resistor. With five band resistor you can get the value like 33.6 ohm, 47.2 ohm and etc. For the four color band resistor, the best value you can get are 33 ohm, 47 ohm and etc. In older design of Monitors you can actually see a small preset at the feedback circuit near optoisolator IC. This preset it tuned to set the B+ voltage to flyback transformer and if this circuit have problem or the preset fails (value run or dry contact), the high voltage will increase and shut down the Monitor.


So in order to prevent high voltage shutdown problem and made sure the B+ voltage is always stable, Monitor design engineers had placed a five color band resistor in place of the preset. With this fixed resistor in the feedback circuit, chances for the B+ voltage to shoot up is very slim unless the five band resistor itself have turned into high ohm or totally open circuit! In some cases, it was very difficult for me to get the exact resistance value (for a five color band resistor) thus i used the series resistance formula to help me get the value that i wanted. Isn’t it fun to do electronic repair work