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Electronics Repair Questions/Answers and Testimonials- Part 77

By on April 26, 2011

Hi Jestine,

I’m so glad to tell u that after reading your smps ebook, testing electronics components and others now i’m well enough to repair any electronic components. Now i’m trusted with so many customers so that i’m about to employ some one to assist me. Thank u so much mr yong u gave me good life. Soon i will send u money for blue esr, i want to invest more in components testers.

Thank u,

Issa A


I am working on a proview monitor and the g2 reading is only 145 dc volts. I took the g2 wire out and mearsured it and still the same reading. that is a bad fly back..right? please advice. Thanks

HI Waleed,

Yes if the B+ voltage is good. A low B+ voltage will produce low G2 voltage.



hi justine,

i just wanna ask help for my power supply which is for laptop used. when i remove the load the output voltage is okay but when i put the load the output is drop what is the probable problem? some of my incounter is capacitor but these time the capacitor is ok what are the other posible defective? thanks sir..


HI Kay,

It can be the power supply or the laptop motherboard have problem. For the power supply you need to check the e-caps with esr meter. If all check to be good then suspect one of the ic have shorted in the laptop motherboard.



HI Shadab,

I would like to express my appreciation for your courtesy in sending to me the updates. I am your fan.
I would like to thank you for your assistance.

You are welcome!

There are a bit more questions which are in my mind that I want to ask, with the hope that I will definitely be answered.
I am running an automotive workshop since long time and leading a good repute in the market. As you know that technological advances are taking place every moment around the world these days. More and more electronic systems are replacing the mechanical systems in automotive industry. The electronic systems like Electronic Fuel Injection (EFI). Engine Immobilizer systems, SRS Bags and so on are getting their ways in the automotives.
So we the mechanics and automotive engineers are facing the troubleshooting ECMs, reprogramming the EEPROMs and decoding the immobiliser systems.
Although these systems are also concerned with the basic electronics components, the testing and troubleshooting is almost the same as in the case of television and other appliances. Please guide me how to have a good control over the problem to test the automotive ECM components.

I suggest that you get this book that have good info on the above subject:



HI Yachad,


I have a question on this Panasonic NV-FJ700AM VCR on my bench.


It came in inop – I replaced the SMPS secondary caps with Panasonic FM’s and now it operates, but with minor glitches.

I’m still on the PSU – see the attached PDF schematic.


The -29V and +36V appear to have excessive ripple – see the scope pics.

The other voltage outputs have much more stable waveforms.

Both these powers use the same rectifier – the rectifier appears to check OK on the analog multimeter. Am I being pedantic, or is this a normal waveform for this type of rectifier?

All DC output regardless positive or negative should have a straight line when measure it with a scope.

Vishay lists a BYV33 as a substitute, but how about using an MUR160, or similar to get a more stable waveform?

You can use UF5404 for replacement on all the secondary output diodes. To get a stable waveform i suggest that you check the primary side filter cap.


Beyond that PSU issue, Fast Rewind RR doesn’t seem to operate correctly.

When pressing RR with less than about 20 minutes to rewind, it doesn’t go into RR mode, but rewinds only slowly.

FF works normally as expected.

Your comments?

I suggest that you repair and make sure the dc output is stable first and then only test the VCR.

Also, I am looking for an upper cylinder for this – a VXP1946 4-head.

Sorry no info on the part.




At the outset I would like to thank you for access to the excellent information in the field of electronics.
My name is Adam I am a Polish electronic engineer living now, and I live in Scotland.The electronics and computer encountered as a hobbyist and then started working in this profession and I know how much time and knowledge every each need to spend on learning.Reading and material on the site of your I think they are really simple and very well designed because not everyone is a mathematician and not everyone can understand the physics easily. Therefore I consider that the materials are well prepared for practical science of the profession.I wish you much continued success in the further development of the website. I would like to apologize for my English, because it is not my first language. All the time I follow the “The Repair Newsletter” and I deeply appreciate the content of these articles.
Best regards.



i have hp 7540 monitor is fault  vertical top folding.hoe do rectify this fault

HI Tamil,

Make sure the supply voltage is good to the vertical or directly replace the vertical ic and retest.



How do I test the Chopper transformer with Ring tester.

Hi Walter,
The primary winding is in either two of the 4 pins. You need to check where the 2 pins goes. one has to be come from the big filter cap positive pin and the other from the drain pin of power fet.



Hi Jestine,


I have this problem with trotter 3300 stepper machine in our gym actually it was 110V and then it was plugged to 220V I replaced the busted fuse and the burned varistor and then I powered up it worked and then now when i try to power it there is no display as if there is no power coming from the machine I checked the parts I replaced but they are OK there is power coming because the LED on the board is lighted for the power and some other LED for motor on and others are lighted.I tried to disconnect the cable for the display module and reconnect it the display came back but when i turn off the main power switched and turn it on agin display is not coming.sometimes I tried to take out the plugg and plugged it again and turn on the power switch the display will come but when I tried to turn off and turn on again the power switched the display wont come.110V power supply is there for the machine but I dont what causes this problem.Thank you very much




HI Dindo,

I believe the higher voltage had caused some damage to the mainboard especially the IC that power up the display. First you just need to make sure that all the output voltages from the power supply are good and stable. If the voltages are good then suspect the control ic.




hello sir,

i test my laptop on other power supply its running ok. then i found that my power supply is the problem. on power supply sir what location must be  probably the problem ? if i put up load the voltage output was the way i already order of your compilation repair book, im looking there my problem but it does not included.

thanks for your help sir.


Hi Kay,

Usually is the filter cap problem



HI Mohammed,

I am busy reading those ebooks, and very happy to meet you.

You are always welcome!

Please I want to ask you more about IC’s, especially testers. Is it possible to get one universal tester for all IC?

No is not possible. Different IC needs different tester.

We have an argument with one of my colleague, that there is  no IC tester. Please send me different types of IC testers and their prices because I want to know more about IC’s

Thanks for your usual cooperation and your continue guidance.

TTL IC tester is for testing digital ic where the part number start with 74lcxx and etc. MCU and EEPROM IC needs a programmer. Oscillator ic needs a pwm tester and etc. Sorry i do not sell tester thus i do not have info on this. i suggest that you search from the internet for many different ic tester.




Hi Jestine,
As I was about to open now the monitor after standby hissing sound appear again and the monitor shutdown again but you could see the display on the screen just it is dim same as the problem before.could it be an indication that I spoil again the backlight or there is really something causing this problem to occur can you give me some tips where to focus on the board to solve the problem.Thank you for your unwavering support.


HI Dindo,

Check to see if there is any different in the supply voltage before and after the problem. If the voltage remain the same then the problem is either in the inverter ic, high voltage transformer or the backlight. If the supply is low or totally no voltage at all then suspect the MCU because if the MCU have problem it will not turn on the start circuit thus there will be no supply voltage to the inverter ic.



HI Jeremy,

I have a power supply for a cordless phone to repair, located the faulty part, an 8 pin DIP package. problem is the only markings on the IC, are the in house marking,

CEA 00842

See Attach. for pic of Supply

the power supply is a dual output SMPS, with Vout 1 = 6.5 Vdc, Vout 2 = 7.5 Vdc, and the Negs are Isolated, so if you were to test Vout using the Neg of the other there would be no reading. You would have to use the neg. of that specific Vout.
Can you provide any help with how to source the company for this part. or some way of obtaining an equivalent.
I have tried searching the net for the company name, part number, and so on. This item was especially manufactured for Telkom in South Africa, and they don’t sell the power supplies separate from the phone, so the customer has no other route but to buy another phone package, which in this country is expensive for an average person.

Noted but i have check from internet and could not locate the datasheet and the supplier that sell this part. This part number could be a customized part number that only the manufacturer know about the part details.



Hi David,

First let me say I’ve enjoyed the ebooks I’ve purchased and the monthly email updates. Very informative, wish I could be one of your students for awhile.

You are welcome and thanks for your support!

I’m an electronic tech. for a casino and I’m trying to find some information on the power supply used on our bartop Kortek KTL LCD monitors so I can repair rather than replace and I’m not having much luck so far.

I was wondering if you were familiar with or maybe worked on power supplies manufactured by a company called AWON. The information off the circuit board of the power supply in question is as follows: AWON
PWB-A006A       output: 12 volts/5 amps

The units very seldom show any visual signs of a problem.

I would like to find information on which components most commonly go bad and possibly a schematic of the power supply. I have attached a picture of the assembly.

Any information you could give me would be greatly appreciated.

Sorry i do not have the schematic. From the picture the primary side (center part) seems to be darker and i suggest that you check the 2 small electrolytic caps with esr meter. If you do not have the esr meter you can directly replace and retest. If it still does not function i suggest that you check all the components in the board since the board consist of less components.

If you have other question please do email me again.




I worked in Sony audio manufacturing plant from 1993 to 1997.

Noted and nice to know you.

I could repair up to component level for any manufacturing defect Sony audio product with the all the required instrumenst, eg power supply, voltmeter, signal generator, osc, and 100% must with the schematic diagram. I cant repair anything if without the schematic diagram. In my opinion, it is impossible that anybody can perform a perfect repairing without the schematic diagram.

It depends on the problem. If there are components burnt or missing components then the schematic is very helpful. Understanding of how the equipment works with the help of schematic could help a lot in troubleshooting. But we do not need every schematic for every model in order to perform troubleshooting.

But there is many expert claim that they can repair any PCB on this planet.

It depends on parts availability, manuals and some other info to be able to repair those boards. I have never heard of anyone that says he could repair any board on this planet.

And i am still searching for their secrect, thats why i found you.


To repair a monitor or LCD or Power supply is easy because you can test it out after the repairing, if cant work then can retry and test again until get it fix before send it back to the customer.But i am not interest on the LCD, or monitor.

I am intrested on the industrial electronics repair, because i plan to start up repairing business for that field.


To repair the industrial production machine PCB eg VMW CPU PCB, AI/O PCB, DI/O PCB, motor driver or automotive electronics, engine ECU, air beg ECU, automatic transmission ECU and..etc

These are the tough boards to be repaired.

There is no way to get the schematic diagram, and there is no way to test it after repairing.

You are right.

So how your course and e-book can help me for that?

I have no ebook on those specific topics you have mentioned. However, if you would like to venture into automobile electronics repair then i suggest that you get this book:

I must deliver at least >90% success repair product back to the customer to secure my business or my company image?


And i cant test the repair PCB result before deliver to them! They have to stop the production, power down the machine, plug in my repaired PCB and get it test.

This is a very costly test!

You are right!

And most of the problem may be intermittence at some operating condition or temperature. Furthermore, now most of the PCB are using IC more then the discrete componet.My final job in sony was to design sony new product, but job no fun because all is in IC, so I left to join intel as production machine maintenance..


Whenever there is machine down, just locate the faulty parts, or PCB, an dreplace with the new part, job done.Down time is more costly then the parts or PCB.


There is many repairer in abroad that they can do that magic job, and i still wonder how they can do that?Do they poses a powerful equipment?

They have the info and good test equipment and manage to find parts.


I can send my customer defect PCB to them for the repairing and earn some fast money, but this cant be the long term, due to the shipping cost.


I prefer to start my own here to bring down the cost.And another problem is where to get 100% required spare part?

It depends on what type of parts you are looking for. From my experience one cannot get a 100% spare parts.

It is no help if you can locate the defect component, but you got no spare part.

You are right. That’s why you must do your homework first before taking in the boards for repair.



Please if you have a transistor A1281 (Y327) SPECIAL POWER OF POWER MODULE
Tevion LCD -4062 Please if you respond.

Once again you can only please one can also 50 pieces
I live in Maribor, SLOVENIA Šentiljska 97
Payment on delivery of material.

Hi K,

Sorry i do not sell components. You can visit the link below to buy the component:

Have a good day!



HI John,

Nice blog, but I didn’t say a way to post a comment there. I also didn’t read about any scenarios there that are similar to the problem I’ve trying to fix.

Thanks and noted.


I have Viewsonic VA703b LCD monitor that will work normally for 10-20 minutes, but then the LCD panel turns white.  If I power it off and then right back on it will display the last screen image properly, but as soon as I do something that causes the screen to need to be redrawn, it turns white again.  Also, if I turn it off and let it sit for about 10 minutes (apparently allowing something that is overheating to cool down), then I can turn the monitor and it will again work for another 10-20 minutes, but of course then it repeats the same behavior as previously described.


While the main board and power supply board are very similar to the ones shown in the manual, there are enough differences that the service manual is not as helpful as it should be.  I should also note that the inverter driver circuitry on the back side of the power board is virtually identical to that shown in the service manual, but they omitted some info that would have been helpful.

I’ve done as much testing as I can on all of those circuits but can’t see anything that accounts for the problem.  Have you seen this type of problem?  Am I looking for the problem in the wrong place?  (I don’t have any info on the circuitry embedded in the panel and was hoping that the problem was not in the circuitry embedded in the LCD panel.)

I’d be interested in buying you LCD repair book, but I need a some (advance) proof that if I buy it would actually help me to easily diagnose problems like these. Thank you for any insight you can give into solving this problem. Please use this opportunity to show me how your book would help me to diagnose this problem.

This problem can be cause by bad LCD Panel or the mainboard. First you need to make sure there is good supply voltages eventhough when the display already turn white. A missing voltage to the LCD controller board could cause it to have white display problem. Next, if you have the scope, measure the signals coming out from the main board. When there is no display and no signals from the mainboard to the lcd controller board then suspect a bad mainboard.



Hi Jestine,

Where can a find a replacement optocoupler for rca lcd tv?  It’s a nec 2561wk913.  Thank you again for all your help.


HI Jeff,

Try this link:




Hi Plgperer,

Dear Sir,many thanks for sending me a reply, this rectangular block is
three pin PTC, pins 1&3 is connected
Across deflection coils and degaussing coil which are connected in
parallel, the center tap which is pin 2 is given supply through one side 1:
1 LF transformer,there ia a 3watt 470 ohm resister also connected in
parallel to the either side of the coils it forms a shunt to the coils,I
checked the resistance of between PTC and 470 ohm R , (coils ends
detached)it reads only about 150 ohms,as to ckeck if I switch on giving
220volts AC to the TV what will hahappen?please reply I read almost all
your Ebooks but did not come across PTC or NTC. Please reply,God bless you

The PTC is a posistor and it can’t be checked using ohm meter. A bad PTC will still check okay. If the fuse is blown you need to directly replace it. NTC is a thermister and is used for surge protection.



hello Jestine, hope you are fine overthere. The TV set I am repairing now has green retrace line, after a few minutes the green retrace line gone and the picture ok already. Is it the G filament get shorted with the heater? I hope to hear from you soon and thank you for your previous repair tips that you send me.



HI Rido,

It can be the tube or the crt board problem. I suggest that you visit this link for some good info:

Sometimes a leaky color transistor also could cause retrace lines.



Hello Jestine Sir,

How are you. I have replaced compatible STR for the HCL HCM780M Monitor SMPS. After replacement fuse didn’t blown. Primary section is OK But the Monitor still not getting turned on. I suspect shorted SMPT Connecting Primay and Secondary section of the SMPS as there is no power in the secondary section at all.  The SMPT has 5 Primay legs and 10 Secondary Legs. Could you please guide me how to test this SMPT and solve the Problem.

Thanking you.

hoping for earlier response in this regard.

Hi Noor,
You need a Blue Ring Tester to test on the primary winding coil. Make sure no shorted diode in the secondary side and no shorted components in the mainboard. Sometimes i do not trust compatible because it can be not working. The best is to use back origianl number and make sure no bad components in the primary side.



HI Rohit,

1.can we test the shottkey diode on board?

No you can’t unless you remove on leg.

2.after switch off monitor is there any voltage present at HVT(high voltage transformer),if yes is it ok or not?or is there any resistor to discharge in inverter boaed?

There will be, in some design especially the ballast cap that hold the charge. You can just directly discharge with the screw driver because the current is small. case of DMM,can i get voltage at pin of backlight connector.(in ac range)using dmm is suitable or not?

DMM is too slow i suggest that you use analog meter.

4.disconnecting backlight can i just measure ac voltage at output of HVT?

Some design will shutdown faster then you get the reading because of no backlight. You need to test it out and see.

5.if i replace 85 celcius cap for 105 in secondary filter line ,what may happen?

It depends on the quality of the caps and some caps could work without problem.

6.thinner solution and pcb cleaner are same or different?


7.for lcd repair ,which oscilloscope is better.means about range?

The best is 100mhz so that you do not need to upgrade it again. You can get digital or analog scope.



sir YONG,


thanks alot for the news every month,i have problem with our video machine name BATTLE GEAR 4-MADE BY TAITO,,,when i switch on the power then it will enetialized,after that a few seconds it will appear ERROR 901,may be you have any idea about this what remedy or section i will cheack,or what this error 901 means?because we dont have any manual about this machine.i hope you could give me any idea about this trouble,,,THANK YOU AND MORE POWER,GOD BLESS…


Hi Cris,

I have not repair any of this machine before thus i can’t provide any definite answer to you. You must get the manual to understand the error code otherwise it will be difficult to repair it unless you have the same board for comparison.



Dear Sir, many thanks for sending us your Ebooks which we gained valuable
on electronics,I can’t understand the following phrase-Most SMPS chassis
have a secondary(or” standby”)SMPS which powers the remote control
circuits.Since the main power supply won’t start if the remote control is
dead,check the secondary supply and the remote control circuits before
testing the main supply and the horizontal output stages.
Please explain this to me.thank you plgperera.

Hi Plgperera,

This mean that the standby power supply need to work first because it has to produce 5 volt to power up the cpu and the remote control circuit. When you press the remote control you are actually sending a signal to the CPU so that the CPU could send a signal to the main power supply. If the main power supply is working, output voltages will be produced to power up all the circuits in the equipment.



Dear Jestine, Thankyou for your Ebook just downloaded. A question about a shock machine I,m trying to build (based on circuit from single-use camera). The capacitor is rated= 330v. 80mf. Is it safe /possible to link 2 of these capacitors in parallel? if so, what would be the total output? Would this be enough to kill rats?

 Kind regards, R.M.

HI Mooney,
Thanks fot the support on my ebook and yes you can check on the link below for the answer:

Have a good day!



HI Abdul,

After a long interval I’m contacting you. Please answer the following.

1) In Benq LCD monitor tuning cap .22µF160V (found near Inv transformer, C5707 and 9024) is AC or DC?

AC voltage. Usually when you buy the non polar cap it is just written as 160v, 250v and etc.


2) Are all the 3 SMPS transformers (the biggest, smaller and the smallest) found in the cheapest PC p supplies (China) same. Can we use same SMPS transformer from another p supply unit. I ask you this because in many PC p supplies circuit design is same but only brand names are different. And the voltages too are same.


No they are different because different manufacturers will manufacture power supply that run on different circuit and voltages/current. The best is to get back the transformer. You can use the transformer if the ohm resistance of the pin out is the same and have the same inductance value on the primary and secondary windings.


3) New Viewsonic 19″ LCD screen is blinking along with power LED. CCFL and inverters found good when checked with LST1 tester. What could be wrong?


If the power supply output check to be good (mainboard supply also good) and stable then suspect the mainboard because the power LED signal is coming from the mainboard.


Thanks for the news letter. With the help of your ebook I was able to repair few LCD monitors.

You are welcome!



Hi Hamzah,

Kerosakan TV tiada power, tiada raster tiada suara.

uji voltage bahagian secondary SMPS dapati ada voltage kecuali diod yang bersambung hingga ke HOT (B+ line) voltage nya rendah dan tidak stabil (naik turun).

Saya menguji primary winding SMPS menggunakan Blue Ring Tester dapati semua lampu led menyala hingga ke warna hijau. tetapi apabila saya uji pada primary FBT dapati kesemua lampu led padam, kemudian saya tanggalkan satu solder kaki primary FBT itu dan uji dengan Blue Ring Tester dapati kesemua lampu led menyala, persoalaan saya:-

1) Adakah FBT itu rosak (Shorted) atau ada komponen di bahagian secondary FBT yang rosak,

Bila test primary winding flyback offboard semua LED menyala tetapi padam bila test on board bermakna ada benda dah short circuit. Cuba check diode kat flyback secondary winding. Ia mempunyai satu ataupun 2 biji diode dan sekiranya diode ini rosak ia boleh menyebabkan masalah tersebut.

2)  Jika saya uji dengan Blue Ring Tester mulai dari bahagian anod (Diod B+ line) hingga ke collector HOT dapati semua lampu led akan menyala hingga ke warna hijau. adakah cara ini betul dan bermakna primary winding pada FBT itu baik.
3) Jika saya uji dari bahagian cathode (diod B+ line) hingga ke collector HOT dapati semua lampu led akan padam, adakah ini cara yang betul untuk menguji primary winding FBT dan ini bermakna FBT itu rosak.

Ia primay winding baik tetapi tidak guarantee keseluruhan flyback baik kerana flyback mempunyai secondary winding, internal diode dan juga flyback divider. Anda kena menguji pin di mana B+ voltan masuk dan colletor HOT.



Dear jestine,
I was having a vertical problem, top half of the screen is blank and the lower half is having picture (  raster starts from the middle of the screen ) on my CRT SONY WEGA KV-XA21M61. I couldn’t find the fault
so please give me a solution

thanks a lot

Hi Ibrahim,

Make sure the supply voltages to the vertical ic is good. If the surrounding components check to be okay i suggest that you replace the vertical ic and the horizontal oscillator ic and retest.




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