Hi Jestine!

Good day!

Thanks a lot for your e-mail.

I’m so glad and happy to tell you that I have already repaired a number of electronic equipment with the help of your ebooks.
It’s not only profitable but the joy of self-achievement are wonderful.

Thanks again and I wish you and your family good health and more power to you on your career!

With my best regards,



What should new electronic technicians do
when they come across older electronic devices or equipment with obsolete components?
like for example
lets say you have a circuit board that was assemble in the early 1980s. the part that needs replacing is a transistor.
how many times does this old transistor
part number has to be cross referenced from the late 1980s, 1990s,2000 etc.
will the part number on that old transistor be in todays cross reference book?

HI Tracy,

Actually it doesn’t matter whether the circuit board components were manufactured in the 80’s , 90’s or now as long as the manufacturer use standard code part numbers then we will be able to check the data according to the databook.



Hi Jestine, glad to write you again.
I ask you something : I had repairing problem on the minilabs laser printer like Noritsu machines. I found a defect on laser module, blue and green laser module. Did you ever know where that parts can buy? Please tell me the links.
Thank’s for reply.
Best Regards.

Hi Marulitua,

I’m not sure if the website below sell laser module same as your type or not:





hi jestine,can you replace any parts with 74LS05?

Since 74ls05 is easy to get from the market I suggest that you replace it with original number. For your information 74ls05 is different with  other 74l series ICs.




I am trying to built a ozone generator based on Electronics for you’s ozone generator. I am using a CFL bulb circuit connected to primary of a monitor’s EHT 7095. but i am unable to remove the built in diode of EHT. please help me that how can i remove the diode from EHT.

HI Raj,

Since the flyback is fully covered with hard epoxy thus it is very difficult to retrieve it. I guess you just have to smash it with hammer.




Hi Sir Jestine how are u? i have a question if the P20NM50Fp

is only a N channel? or it can be a P channel i’m a lil bit comfuse! im fixing a Lcd tv and the defective part is FEt this is the value P20NM50fp i wnna know if this is N or P channel! i found i spare to the other tv with same value but when i try it, it doesnt work! before i solder it i test and compare the orig, part to the one spare part that i found to  the other tv, but it show a different reading i wonder why?! thanks u so much Sis Jestine! take care and Have a good nyt!


It is a N channel FET. Please refer to the link below:


In front of the part number you need to add “ST”.


Morning Jestine, I want advise form you, if i want to order component from Malaysia, where are the best place ? the cheaper but good quality. Please include the email and website because i want to order online. thank you Sofian

HI Sofian,

Malaysia do not have best place to buy components because lots of electronic shops still not online yet. There is one and you can check on their website


You can try to buy from this website utsource.net



Hey jestine,

Hw u?? Now i’m very happy for repairing electronics and lots of information that is new for me, i can’t forget u, and thank you very very much for the reward testing electronics components, and again i’m ready to buy another book from you !! i hope next month i can buy another book !!! So once again thanks a lot and have a great days ahead !!!!!



Is there a direct substitute to the ic 4015?.

No you have to use back the original IC.

On your advance technique to locate shorted component. Is resistance test method helpful in such situation?.

Yes it can be helpful if there is less components in the board. if there are lots of components like computer motherboard then it will be a problem

You said that after finding the SMD capacitor that shorted, you only tested it at 10k to reveal its shortcoming.

Yes because some of them tested good at x 1, x 10 ,x100 and even x 1k ohm.



Thanks Jestine truly appreciates this and I will always be part of your Team. I always say to myself that Jestine is my # 1 hero in this world and I love Humphrey Kimathi(Kenya) and Behzad from Iran with you guys I believe I can do everything with electronics. have a great day!

Thanks again



Hi Jestine,


I recently bought your book on Switch Mode Power Supply repair. I have a bit of component knowledge but haven’t worked to that level for 30 years.

I felt that I had to tell you how impressed with it  I am, very easy to read and understand, and I have not spent a lot of money on tools yet.

An Isolation Transformer, Multimeter a Capacitor Tester and a Light Bulb…so far I have had a 3 from 3 result.

A 32′ LCD quoted as $200 to repair actually cost me $16.

A 17′ PC monitor with no power cost me $1.80 to repair and,

A 20′ Arcade chassis with no power that cost me $9.90 to repair,

Without your book I would have previously thrown these out,  as far as I am concerned your book has paid for itself many times already.

I intend to buy some of your other repair books in the not too distant future.

Please feel free to use this email as a reference.

Best Wishes

Ray Scott,




Hi George,


Sir What is the output of flyback transformer is it AC or DC?

The flyback secondary pins are AC but the anode cap output is DC 24KV.

and what is the supply of the primary windings of flyback is it DC or AC?

The supply is B+ dc volt to one of the flyback primary pin. The other pin because of the HOT switch you will get AC at the secondary pins. This is the same theory as the switch mode power supply transformer in power side.



Hi Jestine,


I came across one of your article that you are making use of this Dick Smith flyback tester. Did you build it yourself?

Since no flyback tester is available in my area, I am a bit inclined to build one. As I tried to check the list of spareparts needed for the project I am a bit fuzzed with the description of capacitors used. (i.e. 0.0470uf MKT and 0.01uF MKT) I think MKT capacitors and Mylar capacitors are two different types as ive seen the difference in the finished prototype .

Pls. correct me…


In the absence of this particular MKT capacitors, what type of capacitors would you suggest me to use?

would it be possible to use mylar or ceramic type of same value and voltage ratings?

What would be the effect if ever?


Your feedback would greatly be appreciated….Thank you in advance Jestine….God bless.



HI Nichole,

Thanks for your email. For your information I’m not the creator of this tester. The creator is Bob Parker and below is his website:

As for the capacitor usage issue, I personally have not try it but you can try. Always use the same value and voltage rating even though they are from different type.



HI Victor,

Thanks.can i replace the 15 inches dell power mosfet with k2643 since i didnt see the exact type which is fbe51 and cant find it in the data sheet?

If the spec is more than 600v, 6 amp 45 watt then you can use it. Currently I’m at home and do not have the datasheet book with me.

Secondly,the two schotty diodes with 3 legs at the secondary power,is it compulsory to replace them if faulty with same type or any 3 legs schotty diode of a different part number can also work.

You need to replace with the same part number or any part number that have the same or higher volt and ampere.

pls guide me accordinly bcos im in shortage of parts especially getting the exact type.

Try get from utsource or logictoyz.com

Thirdly,apart frm transitors and ic that cant be replace with any type except same type or equivalent,can i go ahead to replace any other components on the lcd monitor power supply board with any available part that fits the hole and of different part number.if not yes,pls mention the components that needs exact replacement part number or equivalent so i can always replacement procedures.thanks

Make it simple- components like fuse, resistors, capacitors, zener diodes, are easily found in the market thus there is not necessary to look for equivalent part number. For IC you need original part number. For transistors (include fet) and diodes you need to either use original part number or any part number that have the same or higher voltage, ampere and watt.



Do I need to remove all the components from the circuit board to search for something wrong?


Good to know that you email me for support. This is the real value of getting my ebook. You have a good question-The answer is it depends on the problem and how well you understand the circuit. For example, if  an equipment complaints of no power I will definitely concentrate on the power section. I will check if there is any output voltages or not and if do not have output voltages then i will check on the components in the power side.

Again do I need to check all the components? Yes if I’m not familiar with the equipment power supply design. Even now If i come across any equipment that I’m not familiar with i will check all the components in it. For a consumer electronics power supply I could check all of the components in less than 20 minutes. That is the power of the Testing electronic components ebook because it teaches you how to accurately check on the components. In the beginning you may need longer time but  once you are good in testing electronic components your repair time can be cut short. If all the components check to be good then I will directly replace the power IC and retest.

Assuming if I do not want to check on all the components i can start to check if the power IC have any supply voltage. If no supply voltage I will trace backward to see if there is any resistor have open circuit or not. If there is supply voltage I will most probably replace the power IC and retest after I have confirmed that the corresponding components are good.

If you have any problem in electronics repair just shoot me an email and I’m glad to help you out.



how to be a professional repairer

First make yourself good in testing electronic components. Once you are good in testing electronic components you can start to practice it on junk boards. Those junk boards you can buy it from ebay or any electronics shop. You can also buy electronics project kits online or from electronic shops to improve your knowledge in electronics. You need to practice it and if you face any problem during this time don’t give up-just email me. In the meantime you can join electronics repair forum, buy electronics repair books and even subscribe to electronics magazine.


You also need to know which repair field you wants to be in. If you want to repair LCD TV then get a LCD TV repair ebook and get support from the owner. If you want to repair Audio equipment then buy books related to audio equipment and etc. Don’t forget to read my blog post and check out the comments too. We could learn a lot from other people’s comments.


HI Victor,

if the capacitor is storing charges or voltages during power supply failure,what are the components i need to check for faults?

If it happen in primary side of power supply then check the start up resistor and also direct replace the power ic. For your info some monitor will still hold the charge even thought you have turn it off.

which components are failing if the monitor beeps whisky noise from the power supply when switch on?

You have to check because it can be any component from bad resistor, capacitors till transistors.

if the power led comes on and shut down immediately and no sign of power,what is wrong?

It can be the power section itself or the mainboard have problem because the led signal is coming from MCU. First check if there is any output voltages. If there are good voltages from the power supply then suspect the MCU or the inverter board could have problem. Components shorted in inverter board also could cause such problem.

if the fuse is ok and no sign of power but every power components are physically found alright,which components should i pay attention to search for faults?

Check if the power ic is getting supply voltage or not. Next make sure the output voltages have supply. If no output supply then check all the components in the primary side. If there are output voltages then the mainboard have problem

how do i discover the power ic is bad even though i didnt see any crack or burnt sign on its body?

Check the supply voltage. A shorted power ic will pull down the supply voltage. if you have a scope then check the output pin for square waveform



hi there Jestine Yong i need help on fixing my LCD Monitor its an Acer
17 inch the problem is that the power is on but the display goes very
dark you can see bwa its very dark with it display please i would like
your help on this matter

thanks again

Regard Ronald

Check the pico fuse in the inverter board and it could also have components shorted. Sometimes only the fuse have problem.




Jestine Yong works as an Electronics Repair Lecturer in Kuala Lumpur Malaysia and his training website is http://www.NoahtechElectronicsTraining.com. You can check out his repair blog at http://www.JestineYong.com