Voltage Testing – Every Repair Technician and Engineer Should Master This Skill
By only realizing how to examine electronic schematic diagram and tests digital elements ended up not plenty of to make us a fantastic digital repairers. A lot of faults are unable to be detected even if you know how to correctly examination and examine all the digital components due to the fact individuals faults only can be detected by simply just executing a voltage take a look at. Do you know that fairly a numbers of Keep track of troubles I have to execute a voltage test in order to locate the defective components? Certainly, if without having voltage testing, I may well conclusion up cannot locate the fault and the Monitor have to be return back to buyers. What if you return a lot of Monitors again to the exact customers? Of study course your enterprise track record would be impacted and worst if your competition (other digital repairers) be ready to restore it. You would surely reduce out the consumers and is incredibly tricky to get back his have faith in once again about your functionality to repair service Displays.
I do know tons of electronic repairers primarily newbie’s do not have the braveness to execute the voltage exam specially Laptop or computer Displays and Television for the reason that they were fearful of the higher voltage and get electrocuted. Effectively, if you want to function in this line and pick out not to learn about voltage screening (mainly because of fearful), then you are certainly lacking something that can help you to maintenance any devices rapidly. After all, voltage testing is not that as risky as you considered to be. With some steering from fix buddies or even you take a look at it on your have (simple) and protection from isolation transformer, I do not see any other motives you never want to do the voltage testing. Besides this of study course you ought to know the security guidelines 1st in this electronic servicing field.
The serious hard dilemma now is even although you know how to perform the voltage tests this does not assure that you will undoubtedly getting able to remedy the digital complications! As to why you are unable to clear up the issues relies upon on numerous factors this kind of as:
– How very well you are in being familiar with the functions of electronic circuit (assuming I’m chatting on the Keep an eye on circuit). Some Displays circuits can be really complicated to have an understanding of it.
– How very good you are in tracing the electronic circuit (assuming you are tracing from the source to the faulty components) simply because numerous electronic repairers will misplaced observe and can’t go additional to detect the fault.
– How educated you are in comprehending every single operate of the electronic ingredient. For instance, if no sign flowing to the base of a transistor, of study course there would be no present flowing in between the collector and the emitter. An additional illustration, what do you be expecting the output voltage will be if 100 volts is passing via amongst a 10 ohm resistor and a 10 k ohms resistor?
– At times in get to resolve a dilemma we unintentionally generate even extra troubles thanks to that we do not have the functionality to keep tight the meter’s probes triggering it to contact on other pins even though measuring a elements (states is an IC or a transistor). This would bring about the total machines to shutdown or even burnt the elements. How quite a few of you have finished that prior to?
– We should also know what the selection of the meter environment is in buy to test the digital circuit correctly. For illustration, would you check the secondary output voltages when your meter is established to AC variety? Or would you anticipate a looking at when your meter’s red probe touches on a chilly ground?
From above, these are the matters that you need to know if you want to be effectively capable to execute a voltage examination on any equipment. It is not that straightforward to take in every little thing that I’ve just outlined earlier mentioned but if you have the enthusiasm to do it (I indicate master everything from looking at electronics publications, viewing forum, executing your own useful exam and etcetera) then you are supplying on your own a probability to learn some thing that will certainly profit to you.
In this week’s write-up I am going to display you how by carrying out a voltage exam has aided me to clear up an unusual difficulty in a Laptop Keep track of.
Nicely, this observe with the brand name of MIMOS (this is an OEM Watch) arrived in with the grievance of are not able to modify horizontal dimensions (you can find totally no alterations when the horizontal dimension handle was pressed). The exhibit width (dimension) was large and both of those sides of the show curved inward (pincushion out). For your details, the horizontal dimensions and pincushion circuit have been located in the identical space and equally circuits had been performing alongside one another in get to obtain a motivation exhibit. If a person ingredient in a circuit fails, it would have an affect on another circuit as nicely! That’s why, when the horizontal measurement circuit have issue, the pincushion circuitry was afflicted also (the show curved inward).
Commonly when I see this type of challenge, I would generally verify and check all the parts in the horizontal dimensions and pincushion circuits’ place with my ESR, analog and electronic meter. Most of the time, I could address the dilemma speedy. The frequent faulty components for horizontal sizing width dilemma in a Keep track of had been typically dry joints, shorted modulation diode and pincushion transistor and capacitor opens together the horizontal dimension coil’s line. But somehow I could not locate the defective factors in this Observe for the reason that all of the factors that I’ve checked ended up all examined alright!
Considering the fact that I have checked all the components in the horizontal sizing and pincushion circuit spot to be all right, now the only way to address it is by way of employing voltage check. Frequently, whenever if you want to perform voltage testing, a single have to begin from the supply 1st. Nonetheless if you are experience sufficient you can constantly skip some area and commence tracing the circuit that you believe would fall short. As there are numerous electronic maintenance newbie’s in this ERG member web-site, I would show all of you how to trace from the source initially.
Now believe very carefully, what would make the display to turn out to be modest or big each time the horizontal size command was pressed through the On Monitor Exhibit (OSD)? There will have to be a sign sends out from somewhere to the horizontal sizing circuit in buy to management the exhibit. Am I proper? The pincushion transistor has a foundation pin and if this voltage may differ (simply because of the horizontal measurement regulate both set to minimum amount or optimum) the display will adjust way too. You can decide on to trace backward starts off from the foundation pin of the pincushion transistor or start from the supply. I will guidebook you to trace from the resource because after you know how to trace from the source, you would be equipped to troubleshoot and mend other Monitor challenges too such as can’t command the brightness, distinction, vertical and horizontal peak. You may well use this method that I’m about to show you in Tv and other electronic tools as very well.
Initial you ought to recognize what is the function of digital to analog conversion (DAC) circuit. Considering that most of the modern day Displays are using electronic sign (conversation between the CPU and EEPROM and other circuits as well) there will have to be some circuit to convert the electronic sign to analog sign in purchase to travel the pincushion transistor and other folks electronic circuits also. Our normal multimeter can not evaluate electronic signal, it can only study analog sign. Older Monitors have the DAC IC situated out web page the CPU (such as the TDA8444 IC applied in NEC XV 14 Keep an eye on) although for present day Screens the DAC IC is designed into the CPU. I guess you are now comprehended why a electronic circuit demands a DAC as portion of it finish circuit. In other text, the DAC is demanded to talk with the analog earth!
In this defective Keep track of, I really don’t see any DAC IC nearby the CPU so I presumed that the DAC was already created into the CPU. Now, this is the most complicated aspect wherever you have to very carefully modify the Check situation and oneself so that when the Observe electrical power is swap “ON” you can perform the voltage check on all the pins at the CPU. Assuming you have taken all the important safety and precautions now is the time to swap on the Keep an eye on and commence to do voltage screening.
Just after you acquired hold of the Check, select the horizontal dimension control through the OSD display. You could see when the “+” and “-” buttons was pressed at the entrance panel, the variety in the OSD display screen indicates the minimal and maximum benefit representing the size of the display screen staying altered. Considering the fact that this is a faulty Observe, despite the fact that the selection in the OSD display screen is changing (mainly because you are urgent the “+” and “-“) there is no effect on the show and the display stays huge and curved. But someway you could measure the pins at the CPU to identify which a single of the pins the voltage is changing when the adjustment button is press! Try 1 by 1 of the CPU pins right until you saw just one that has influence when the horizontal measurement manage was pressed. The voltage is about to 5 volts (depends on the style of Screens) and need to go up or down momentarily when the horizontal dimensions adjustment is modifying. Congratulation! You are now have decided the supply of the horizontal size circuit. A person term of tips, a defective CPU or a corrupted EEPROM information could lead to no signal at the horizontal dimension resource pin!
After you have recognised the pin then it is somewhat uncomplicated to uncover out the fault. Commence tracing from the pin and see at in which the voltage had missing as revealed in this image. Incredibly the voltage stays okay even till pin 5 (inverting input) of the quad operational amplifier LM324 IC. Since this is an OP-AMP IC, it calls for two inputs (inverting and non-inverting input) to develop an output at pin 7 but the voltage at pin 7 would not differ. And if this output won’t differ certainly it won’t be able to manage the horizontal sizing. Pin 5 voltage of the LM324 IC varies and pin 7 will not differs then most in all probability the challenge is either in the IC by itself or elements that are relevant to pin 6 (non-inverting enter). I observed a wire coming from leading of the board and upon inspecting it it was from B+ voltage (about 66 VDC) and passing via a resistor in advance of reaching pin 6 of the OP-AMP IC. Working with my analog meter to evaluate across the higher ohms resistor (820k), I uncovered it to be zero voltage. In order to genuinely ensure is the resistor fault, I desoldered a person of the lead and check with my ohmmeter. Guess what? The resistor has open circuit! Unbelievable and it was real! Changing with a new resistor restored the show back to usual.
Summary- Think about if I did not use the voltage screening method, I never know how lengthy that I am going to shell out on troubleshooting this type of trouble. And worst nonetheless, I could finish up won’t be able to clear up the difficulty and return the Check again to my client. With continuous finding out and apply in electronic restore you will have no problem in tackling any electronic faults in the long run. Just never give up and go on to understand from the ERG member’s webpage. Thank You for getting my member.
