Long Time no talk, hope all is well.
Yes I’m fine thank!
Jestine, I am working on a Dell W1900 19 inch LCD Monitor. The problem is all I get is a white screen and no display not even the OSD menu. The smps power supply is working correctly, the main board does turn on and off the main power led which turns red after 30 sec. I have all the correct voltages on the main board at the regulators, and have a nice sine wave with the correct freq at each crystal.The Inverter board is working because I get a nice bright screen. My attention is on the T-Con Board.
My question is that on the T-Con board I found a SMD component marked “P” . I get 5 volts to this component but only 500mv out of it. Is this more than likely a bad PICO Fuse? It has the same layout as a resistor.
There are many types of marking by different manufacturers and many times it is confusing with the board marking. If the 5 volt is the supply line to the rest of the t-con board circuit then 500mv is abnormal. It could be the component itself have problem or some other component in the downstream have shorted or turned leaky.
Will you please tell me,what is shorted posistor means?Thank you. Tashi
Posistor is used to control the degaussing of the crt tv. If it is shorted the fuse will blow. It is a small square box nearby the ac power supply area and it cant be tested with meter . You need to directly replace and retest.
I am interested in finding a good quality DMM for electronic repair. I want to be able to troubleshoot resistors and other components without removing them from the pcb. I am told certain DMM that have less resistance and are better suited for this task. Right know I am looking at the fluke 179.
Components like fuse, small inductor and electrolytic capacitor can be tested on board. The electrolytic capacitor have to be tested with Blue ESR meter. Other components like transistors, diodes, zener diodes and etc have to be tested off board for accuracy purposes. For resistors it depends on how they are connected. If they are connected in parallel with other resistors there is no meter can test those resistors on board (eventhough you are using meter that have less resistance). Usually i will remove the resistors and test it off board because if i miss just one resistor then the rest of the troubleshooting will be a waste of time.
If you have other question please do email me again.
Good Day! I am derick from the Philippines.I just want to ask if the unit you are selling is the second edition of EDS.How much will i pay for the package to be sent here in Cebu City,Philippines?
I’m no longer the distributor for EDS and you need to email them for more info. Now I’m selling BLUE ESR meter.
Do you have any tips on how to remove the capacitor easily on a double sided computer motherboard?Its really a pain in the ass in removing the capacitor.Im planning to buy a Soldering station but im still confused on what to choose.Im targeting Hakko or Goot. Also, if i will buy one of them,what will you recommend?A Soldering with desoldering like the HAKKO FM-203 or just the soldering station only.
If you have the budget you can buy the hakko/goot vacuum desoldering pump. If you do not have the budget you can get a dual mode hakko 981 solder gun. Apply some solder onto the capacitor 2 pins and heat it up and at the same time pulling the cap out with your other hand.
Hope this helps!
I have got a problem with my sansui TV set (model No. SV2928). I
increases and decreases the volume on its own. It sometimes changes
the channels seconds after seconds. What could be the problem?
If the output voltages from the SMSP are good and stable then possible the eeprom ic have corrupted.
Dear.. Justine Yong..
thanks for the support ,, i in joining reading your electronics repair guide. I appreciate your knowledge and effort. .. Super” the best i ever had””” . I gain knowledge and technique ,, how to repair, troubleshooting and weakness of component”’ . My knowledge in troubleshooting is being upgraded.. thanks for the articles..May God Bless You Always”’
Bio medical Service
I made some measurement mistake and burnt the transformer in the bench power supply. The PSU is of
a switch mode power supply. If there anywhere I can get a replacement for specialized transformer. This
has multiple windings.
Smps transformer is the hardest to find because they are unique. One has to find back the original manufacturer for the replacement part.
Hi sir Jestine,
I just want to ask if the Automatic Voltage Regulator (AVR) and Isolation Transformer are the same? because the AVR also got an output voltage of 220vac.
Thank You and God Bless..
Please refer to this link:
hi , plz tell that how to test the ceramic resonator “H455E”, i will be very thankfull to you.
Yours should be 455khz and you can test it using a crystal tester or power it up and test it with scope or frequency tester.
I am age 57 and repair domestic appliances, washing machines, dishwashers etc. for many years I have noticed appliances changing more to rely on electronics. I found myself not being able to repair appliances when the PCB had gone. It was a wasted call out and making no money. So I decided to try and learn myself. I looked on the internet and found purely by chance your website, after a lot of thinking should I or not down load this book in the end I went for it. I am very glad I did after a few pages I was hooked. I now have my first ESR Meter. The knowledge I have on PCB is limited to looking for bad solder joints and capacitors with a bulge in them.
Nice to know you and you were right that appliances nowadays are using electronics pcb board. I even had a student that repair air condition came to took my repair course. Glad that you liked the ebook and have invested on ESR meter.
I have multimeter and insulation tester for testing elements and motors but PCB are in a world of there own. Can you answer me a question please? Whilst I was using my shiny new ESR Meter I noticed something there is a small + sign on the board I presume this is so you don’t connect the e-cap the wrong way around. is it possible the manufactures of the PCB I am trying to repair have fitted an e-cap the wrong way around that is the – side of the cap into the + side of the PCB. I looked at some other PCB I have collected and they seem ok. This board came off a washing machine that had flashing display lights. I know the customer has had Hotpoint replace the board twice in twelve months but now it’s gone again and out of guarantee. I am thinking could it be a bad batch of PCB, s but if so why have they lasted so long if the e-cap is connected the wrong way around.I feel I want to replace the cap but the other way around. But dare I. Please see attached photo to see what I mean.
Sometimes the pcb designer could have wrongly printed the marking. I came across one similar case like yours and it was found in the crt monitor power supply. Since it is already working for sometime then this mean the e-cap should be connected that way. One way you can find out if it is connected the wrong way by tracing the circuit. If the negative side area circuit is going to a positive output (say from the pin 3 of a 78 series voltage regulator) then you know that the designer have it wrongly printed.
The e-cap is 680uF 10v my ESR meter measures 1146uF 0.03Ohms with the cap in place.
Which ESR meter you are using because the best to test the e-cap capacitance is to remove the cap and check it off board. If the cap value still 1146uf even tested it off board then you may need to replace the cap.
I would like to know how I can check Fet on the circuit with digital fluke multimeter.
Digital meter is not accurate in checking fet. You need an analog meter and the details of checking it i have compiled into an ebook.
Other thing if we have FET on the circuit, but there isn’t anything written on ot how I can find datasheet or more information about this FET?
It will be tough. You need to look out for the schematic or trial on error by using different part number. Sometimes if I’m familiar with that type of equipment, even if there is no fet in it i can always get another substitute number.
Thanks Jestine for another good article I find it very interesting and look forward to all your courses.
You are welcome!
As there are many Computer repair Techs and electronic techs I wonder if the Market for LCD Monitor Techs
is saturated in the US? In other words is there enough work?
Repair tech comes and go. It depends on how you run the business. If the item that you repair have no reliability and you do not provide good service then your business may need to close down. Your country population of more than 300 million should have opportunity on this. Besides LCD Monitor you can add in more repair item like LCD TV, Plasma tv and etc.
Wow bad Capacitors this problem with Capacitors is called Capacitor Plague by a Computer repair Guru.
Noted and thanks.
you say the red one is a metal oxide varistor and the other one is a capacitor
do you know what the rateing is for the varistor the information is on the pic
H C 3
13( )L1( )
what do these or what is the code for this
I need to know so I can replace them thanks so very much
The codeing can only be understood by the manufacturer. if you want to get a replacement then go to electronics shop and ask for a 255 or 270 vac varistor if your country is using 240v line. You do not need to tell the seller the part number. Just ask if he have any 255 or 270volt varistor and they will give it to you.
I have a problem with Dell E153EPC LCD monitor. I cannot power it on. I have changed all the capacitors though they are still good. I have changed diode 911.
The opto coupler is ok so are the resistors and polyester capacitors.The 4 transistors tested good off board .
The rest of the diodes are good. Even the SMD diode at the back of the board is ok. Fuse and varister tested good.
I did not change IC SG68410. I don’t know how to test the IC to find out if it is good or bad.I don’t know what other problem it has. Only you can see it and do it.
If there is zero output from the SMPS and you have check all the components in the primary side then most likely the power ic have problem. You need a scope to test it . Usually i will not use scope, i will just directly replace the ic and retest. If it still not working i will keep the ic for the next repair. if it work then i consider the job is done.
Can you power a SMPS when it’s not loaded?
Some can but to some you need a load.
If so, can I or should I provide an artificial signal back to the SMPS so it thinks it’s loaded and will turn on all of its circuits?
It will be a tough job because usually only the smps designer knows what are the right signal to get it run. I came across certain Power supplies that only requires the same motherboard to run. I connected the power supplies with other brand of motherboards (the connector are properly fit) and it just won’t turn on. Using back the original motherboard, it worked like a charm.
However to some power supplies will run on any load that you have provided like connecting a light bulb or a high wattage resistors.
In page 85-86 (transformer) you mentioned that ..there is still one disadvantage of this method (using blue ring tester) as the winding can go shorted under full operating voltage eventhough windings checks okay with ringer test. So, why the same technic is not mentiond in page 55-59 (coil/inductor testing) as there are also windings (but only smaller).
The blue ring tester is meant to check on bigger coils that have more windings. Since smaller coil have very less winding chances for it to go short circuit is almost zero.
In page 85, while checking windings of transformer, how to know which ohm reading is good or bad? For instance,on primary winding the ohm is 0.768 kilo ohm and sec. winding is 1.2 ohm (page 85) , how to know these are the okay reading? how to know the range of okay reading and the range of not okay reading?
Different transformer have different value thus we can’t know if the winding value is correct or bad.
The above checking is to determine which side is primary and which side is secondary. The above testing also could test for any open winding.
This board in the attached photo has 2 bad zener diode. One flips both ways, the other no filp at all. The problem is I couldn’t see the voltage rating, do you have any idea how to know it?
Flip both ways showing the same ohm value means it is shorted. If not then you can use a zener diode tester to find out the voltage rating. The other one that was not flip at all means it has open circuit. Assuming both zener diodes have problem then i can’t tell the voltage rating except to get the schematic or compare with a good working unit.
Another question is about the voltage rating of a fuse. Do you know why a fuse has to have voltage rating too?
If there is overvoltage the fuse also will blow. In USA their fuse is rated at 125 volt and in our country the fuse is rated as 250volt.