hello sir ,

mine smps getting off after every 10/15 minutes . what would might be the reason behind that . plz reply me on my email-id ,,

eagerly awaiting for your reply ,,

Hi Chan,

Dry joints, bad components, decayed glue problem and etc.



Hi Jestine,

I have been following your posts for two years now, and i appreciate
for the materials you bring they help me in my dairy repair work. I
was just an IT technician with no electronics knowledge but when i
started following your posts i saw a way wide open and began digging
deep into electronics books. I am glad now that am an IT-Electronics
technician working for a large company. Keep it up, for others out
there who inspire to become technicians one day. I will be glad to be
sending posts to you in the future to help others the way you helped

Best regards,



Hello Sir,

Thanks for sending the links about electronic repair books.And
I am reading all your electronic repair articals and Iam not even onot
knowing to check the capacitors and resistors,and also transistors.But
now I am able to check the damaged electronic items like
capacitors,transistors,resistors in Computer Motherboards,Smps and
also in CRT Monitors.
I am very thankful to you because you have given me a good links with
your articals.I am reading your all sending mails.Because of that I
learnt to check the electronic components in the circuitboard.

Thank you very much Justine young sir.



Hi Young, Am Ssenyonga Williams from Uganda

I enjoy ur guide lines but I would like to know the transistor I can replace with the power transistor, number C5297. And C3807.

I found my TV shorting and blowing fuses, after troubleshooting I found the Capacitor ok and the transformer then I came across the shorting transistors but the y are not common in our town.

Thank you for your help ever.

Hi William,

According to my databook, the equivalent part number for C5297 is 2SC3896, 2SC4758, 2SC5148 and 2SC5067.aS FOR THE C3807 sorry no equivalent number for this.

Check also this link:


You can buy online for the above parts: 2sc3807:




Hi Jestine
The artical make a lot of sence you know ……a man keeps saving thing up for “that one day use someday” but never needs it.  Untill you throw it all away then by the time it is no longer there then you need it.  I’m working on my first tv now that i received from n place that have put it on the street now i need to learn how the power-supply section works.  But i still need to learn how to read diagrams and know how the power flows from one part to  another………. still got a lot to learn!!
One question … What is the differences between BUZ 91A , D2499 AND D2498…. cAN ONE OF THE D24…PARTS BE USED IN THE PLACE OF THE BUZ 91A …………….I’ve found out from a nother that the D 2498 and the D 2499 is used as universal parts on a lot of old tv. is this true……..and witch one gets used to work in the power supply section

best regards

Hi Len,

BUZ91A is  FET and D2499 is a bipolar transistor. They are both different and you can check the link below to see the differences:


Both can’t be interchange because transistor have switching timing. If the timing is not accurate the transistor will work in a stressful way and burn.



Always mr.jestine yong but i have problem i’m share with you about the lcd monitor that currently repairing stuggle to find culprit.The lcd monitor that i was repairing is samsung lcd monitor 15” white casing and the problem is normal display but there’s a flickering or like blinking light on display monitor i thought it’s the lamp or the backlight.am i right mr.yong?can you pls. advise what is culprit the power supply or the main board?

thanks and more power…

Hi Jojo,

It can be caused by unstable voltage or one of the backlight is already weak. Make sure no bulged e-cap in the power/inverter board.



Hi Chee,

Would like to know whether testing procedures for surface-mount components on PCB the same as those non-surface mount?

Yes except certain smd transistor are digital transistor and the readings are quite different from the bipolar transistor.
Also, what is the label for a fuse component written on the surface-mount PCB? Is it F something?

Yes and it can be some other label because nowadays manufacturers don’t follow according to standard marking.

Does NR something means that the component is a resistor?

You may need to check it out because nowadays have many funny number. If it is two legs then check the resistance.
As for the sticky gluey white thing on found under the capacitor in page 103 of the Testing Electronic Component ebook guide, what is the thing and what is it for?

Those are silicone to secure the component (from vibration during transportation)
For surface-mount capacitor, is it alright to test the capacitance without unsoldering the leads?

You need to solder it out unless it is an e-caps that can be tested with ESR meter.

I noticed that the ebook did not state exactly how to test for capacitors. What is considered as a good capacitor and what considered as bad? (In-circuit testing possible?)

Non polar cap- use digital capacitance tester (a good cap should have within +/- 10% tolerance

Electrolytic capacitor- use ESR meter and refer to the chart in this link. Any bad cap is more than the ESR value printed in the table. Ex-a 22uf 250volt have 3 ESR ohm and when you test a 22uf 250v cap, the value has to be lower than 3 ESR ohm.



Jestine I have a 1000mf 25v capacitor in my television sound circuit which is reading 947mf.
The ESR reading is good,can you tell me if I should change this capacitor?

Hi Tyrone,

Although it is not serious but i will change it because after few month to a year time I’m afraid the capacitance value will drop and cause intermittent problem.




Hi sir,
I have one MSI 945 motherboard,when it shows display,it’s working ok,but if i switch off pc then quickly if i start it again that doesn’t shows display later on if i take a gap of some time then it’s show display.i thaught it was heat problem but nothing is wrong with processor and not with m/b,fan is ok ,H-MONITORS SHOWS 50-60 TEMP,i have cheched all caps and they are ok.AFTER SPENDING LOT OF TIME I AM REALLY FRUSTED…PLEASE GIVE ANY CLUE…


Hi Vikrant,
Sometimes this problem can be a bad power supply. If the power supply intermittently sent out the power good signal the motherboard will have no display problem.



Hi justine,

I am a self thought technician. I usually fix TVs. Can tell me what is wrong if the tv is expiriencing a straight horizontal line across the screen?

Hi Ivan,

No supply voltage to the vertical output ic, dry joints in surrounding components, bad vertical output ic,open vertical yoke coil and even missing vertical signal from vertical oscilator IC.

Hope this helps!



Hi Peter,

Finally my special “practical problem”: How do you manage to desolder with such ease.

I have a solder sucker but it always takes me multiple attempts to get components “off board” – the consequent risk is obvious.

So a request – Please do a video of just how the ion & sucker are used. Must I become left hand adept, do you need each hand to hold one tool etc etc.

Actually there are lots of videos in Youtube showing how to do this. I will not make a video just for that but I can explain to you how to do it.

First- your sucker (desoldering tool) has to be the normal type .Not the smaller one. Bigger has more suction power. It has to be clean too.

Second- Get a good solder gun with dual mode. I’m using a hakko 981 dual mode solder gun. If you press the solder gun it will have 130 watt. Common solder gun in the market are usually ranging from 15 to 30 watt which is not good enough.

Third- You can apply some soldering paste.

Fourth- Now place your solder gun tip on to the solder joint side way. let it melt first and remember to press the gun for extra hotso that the solder can melt easily. No

Fifth- Now aim your sucker onto the joint while the solder gun tip still at the side way. Then press the sucker and the solder will be immediately be removed.

Note: If you are removing the unleaded joints then it will be hard to remove it.

Hope this helps!



Hi Jestine Yong,

When I have started to read your articles and E-books, I was dummy,
but now I can also speak the electronic repair language and it is
because of you. Many thanks to you. All of my success credit goes you
only. Thanks again.




Hi Devon,

Currently I’m using the Pony prog from lancos.com but you may need to solder the smd ic onto the board and then desolder it out. There are tons of programmer in the market thus I’m not sure about the different in prices. Choose the programmer that suit your repair need. Not all programmer can support the chips part number you are dealing with.



I have a question for you.
i have a lap top charger that produce 19 volts 6 amps. when connecting to the laptop, I could see the stand by power light is on, but when I try to push the power button, the laptop does not work. I checked it with a volt meter and I could see the 19 votls steady but seems like when it has a load on it, it stops working..in this kind of case, what is usually the problem..let me know
i used a 12 volts car light and it was steady and very bright. I could not find 24 volts light bulb to use…would the 12 be enough to test it?
Mr W

Hi Waleed,

You need a 24 volt to test on 19 volt ac adapter. In your case it can be the problem of ac adapter or there is something shorted in the motherboard. Laptop repairer usually will have a dc voltage regulator power supply. If there is something shorted the repair tech could know by looking at the DC amp consumption draw. If normal current draw for a laptop is 1 amp and suddenly the bad laptop have 2 amp current draw then you will know something have shorted.



Hi Jestine, I have one for you. I am testing a bridge rectifier GBPC3508W (1000V-40A) and I am using my Analog meter and the measurement are as follows:

+ to  ~ and ~ to +, reading one way only – Good

– to ~ and ~ to -, reading one way only – Good

~ to ~, No Reading in both directions – Good

According to the readings above this rectifier should be a good rectifier but when I place a and AC 110V across the AC pins and measure the DC out I am getting 98Vdc. what do you think Is this rectifier good or bad?

Hi Andre,

Yes this bridge is good. The reason you got 98 vdc is because the main filter cap already open circuit or along the line from the bridge to main filter cap have open or broken circuit track. Sometimes along the line have a protection low ohm resistor that can be open circuit.



Hi Jestine, According to your books a Diode should mark “D” or “ZD: for Zener. attach is a picture of a diode in a power supply that has a marking of “CR1,4 and 5” . What is the markings name? also there is a Thermistor that has the same marking “CR2 RT1” I don’t understand the markings. There is another component at the start of the power supply mark “SG1” what is this? Need your help.

Hi Andre,

A good manufacturer will always follow standard coding system. This manufacturer came out with their own code thus giving problem to the repairer. As for the SG marking it could be a spark gap. If it is a spark gap then there will be no reading either way using analog meter set to x 10 k ohm.



Hello Sir, i am from kashmir and i have a question that is i have an intex television and i displays blue line vertically on screen.It has CRT monitor?


Check the horizontal yoke coil area for dry joints, bad component. Sometimes an open horizontal yoke coil winding also could cause such problem.



i have one unit power supply got problem . That problem is their power voltage is no enough size because transfomer voltage indication require 28 voltage but i check it only got 13 voltage. i also use osciloscope check signal power also same AC site ok but DC site no ok especially output checking power is too low voltage.

check other component part got faulty i have replacement it likes resistor.   any ideas you can share with me or have you face like this symptoms ???

Hi Hino,

Transformer AC output voltage or transformer DC output voltage after the diode? If the DC output voltage is rated as 28 volt and you got 13 volt then the filter capacitor can be a problem. The output diode also can have leakage. If your power supply is using a linear power supply then make sure the it has enough AC voltage at the secondary side.



Hi ,I use tthe same panel on other CRT it was ok and moreover what can be a sign of a bad CRT.Thanks.

Hi Kasim,

Bad CRT can be blur picture, too bright, no display, arcing internally.



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