Wednesday, January 14, 2015

21 inch Samsung CRT Television takes too long for picture to appear now repaired.(Model CS-21Z67ML)

This Television belong to a colleague of mine, the complaint was that the Television was taking long for the picture to appear.

Upon asking him the history of this TV he told me that it started by taking  2 minutes for the picture to appear, then 5 minutes, 15 minutes,30 minutes and now it was at 1 hour when he decided enough is enough and hence that is how I came in to try and sort out this problem.

Usually I take the board with me but in this assignment I had to take the whole TV for live testing.

After reaching my workshop I opened the TV and went straight to small circuit board at the back of the CRT tube.

First I observed the heater and found it was lighted and hence gave it a clean bill of health.

After that I decided do voltage testing around this circuit and I started with the RGB cathode pins and this is what I got.

R Cathode pin=142 Vdc
G Cathode pin=144 Vdc
B Cathode pin=146 Vdc
Heater voltage=4.4 Vac
Screen(G2)= 95 Vdc

I was happy with the RGB readings but I was not happy with the Screen voltage at 95 Vdc, I was expecting around 300Vdc and here I was getting 95 Vdc.

First I suspected the G2 Capacitor may be failing under load and therefore I lifted one leg from the circuit and re-tested again the voltage at the SCREEN pin and still got the same result and with that I concluded this capacitor was okay.

Then I sifted my attention to the fly-back transformer looking for the SCREEN voltage adjustment knob
I used a screw driver to turn the knob slightly looking at the screen for any change and I was surprised to see light on the screen.

I connected the antenna and YES! There is now picture on the screen, I decided to re-test the G2 voltage again and I got 106Vdc.

Increasing the Voltage caused retrace lines on the screen to appear and therefore I concluded the 106Vdc was the optimum voltage for this TV.

I tested the TV by switching it off and then on after some times and the picture was still coming up immediately.

I did it again one more time this morning before going to work and the result was still the same…the TV is back to normal.

The approach I have used to troubleshoot this problem is pegged to the fact that there was HV present.

This I confirmed by the fact that the heater whose source is the fly-back was ON and therefore the HOT, fly-back, Drive Circuit are working and not considered for troubleshooting.

If HV was absent then I could have used a complete different approach which I have outlined in my latest ebook CRT televisiontroubleshooting guide.

See you guys
Stay safe

Wednesday, November 26, 2014

PayPal now covering the whole of Africa

How to purchase your books from Nigeria

I write to investigate on how to purchase your book and ESR meter. I am a Nigerian working with one of the private university. Please send your details about the payment and the prices.
olawale muftan

Every week I receive emails like the above from interested customers from many countries in Africa asking how to can make payment from countries not covered by PayPal.

The most affected countries were Nigeria, Ethiopia, Zimbabwe, Uganda, Rwanda etc...

The good news is that now these countries of Africa and many more are now covered by PayPal and now you can buy online safely at the comfort of your house.

For more information click on the link below and see if your country is covered and just log on and register with PayPal for free and there you go.

happy shopping

By Humphrey Kimathi

Wednesday, November 19, 2014

21 inch LG Super slim Television dead

A friend of mine referred to me a client who wanted her TV checked by a technician. I usually carry with me a small digital meter and a screw driver because most of my job are done in a freelance kind of setup.

This is because i have another full time job very different from electronics repair which i do as an hobby and also my plan B.

My friend it is good to have plan B in this life because even if you are employed one can be retrenched or loss your job but no one can sack you from using your hands(talents).

For this particular  day i forgot to pack these tools of trade. So after the request i almost gave the lady the following day appointment but since she wanted to have her TV back due to high demand by the children,i inquired from her if she has a screw driver in her house and promised me that her husband is a computer guru and therefore he has all manner of screw driver sets in her house.

With that i decided to attend her  case on the same day. When i reached on site, true to her words she went into one of the rooms and she came out with a bunch of screw driver(all sizes) and i pulled out which i thought was best for the job.

Before opening the TV she connected me to her husband via cell phone for some briefing.The husband told me he suspect the switch because some times the tv had problem to power on when the power button is pressed.

I took that information seriously and to confirm the switch is okay or not i pressed it till home and still nothing  happened on the screen.

I pulled my voltage tester stick and it lighted when brought near the tv. This confirmed to me that the tv is getting powered and therefore there could be something else blocking the power.

So i undressed the TV and took with  me the motherboard to my workshop for further testing.
When the lady was packing the board into a plastic bag, i heard her scream and told me that she got a shock from the board but i didn't take her very serious.

Back to my workshop, i pulled my meter and tested across the main capacitor(220uF/400V) and to my surprise i got 242 Vdc just hanging there.

Then i remembered her words of getting a shock, with that i realized how lucky she was because if she could have touched directly across the two pins of this capacitor it could have been a different story all together.

Lucky was i too for packing it in a polythene bag (poor conductor of electricity) otherwise i could also be in trouble, thank God non of the above happened.

After discharging this capacitor using the series bulb, i started to troubleshoot it.

Because the complain was set dead, i started scanning the primary side of the power supply and looking at the power switch it reminded me of another TV of the same model which had a intermittent  switch problem.

I pressed the power ON switch and clicked how they do when fully engaged but testing across the neutral line of the switch i noticed the switch was open and because i had such an experience i just soldered a jump wire between the two pins of the switch.

I thought the problem is now solved but to my surprise the TV has no voltage on the secondary side.
So i decided to test components on the primary side, just by coincidence i started with the capacitor which filter the Vcc pin voltage supply to the control ic which was rated 22uF/50V.

I was doing this from the bottom side of the TV board and when i tested across this capacitor my ESR meter registered an abnormal ESR reading as you can see here.

For your information a capacitor with ESR of 5 ohms can completely cripple a whole 47 inch LCD tv and here we are talking  91.80 ohms.

To be sure i was testing the correct component i decided to solder it out of the circuit completely and test it again and truly my fears were confirmed as you can see here.

I salvaged another capacitor from the junk and after testing and finding it to be in good health condition i replaced it.

I applied power again to the board and this time i got a voltage at the secondary side and i concluded that the issue is now fully solved.

I went back to the owner the following day and after re-assembling the board back to the tube the tv came back to life.


I strongly advice technician to be on lookout for this kind of switch because even if it is switched off still there is power on the live line all the way to the main capacitor but no return, therefore if you touch on this line by coincidence assuming the power switch is off then you will provide a very good ground and hence get electrocuted

This also explains why the voltage tester pen was lighting when brought near the TV.

Humphrey Kimathi

Author CRT Television troubleshooting guide

 For more information about this book click the book cover.

Thank you guys

Stay safe

Wednesday, November 5, 2014

My new eBook “CRT television troubleshooting guide”

After five years blogging and interacting with many technicians across the world doing electronics repair majoring in CRT television and listening to their most pressing issues on their line of repair I have compiled a book which will demystify CRT television repair forever.

The book addresses over 18 common CRT TV problems and how to solve them with ease.

Stay safe


Saturday, October 18, 2014

Need help in troubleshooting CRT Television problem

Dear Sir,
My Name is Yogesh, I am from INDIA.
I am one of your fans and I regularly visit your Blog for technological update.

Sir recently I came across the CRT TV Problem that there is intermittent fluctuation on the screen and picture shaking vertically (maybe overloading).

I have opened the TV and found China make kit with
Toshiba IC.8893CRNG7D65.

I need your help to troubleshoot the problem sir,
can you help me if possible.

Thanking you-Yogesh

Monday, September 8, 2014

Blog follower from Philippines want to know a few things about CRT television repair


Good morning, I read your article recently: the Understanding of CRT television critical voltage test points...

I was confused a little bit about the word B+ ...I want to clarify this because as a newbie in the field of electronics, safety first is my goal when rendering my services to others...

My question is this: all transformers “s.m.p.s transformer, drive transformer, and the fly-back” are producing a B+, right?

Transformers do not produce any voltage Alex, they just transform (change)

For example they can step down or step up the voltage/current.

But remember you cannot have the two (current and voltage) being increased or decreased at the same time.

Take for example the transformer used in your radio rated 240VAC to 12VAC.

The 240VAC is stepped down to 12VAC, in this case we will have the voltage decreased but the current will increase and that is why you see the output wires of most step down transformers are thicker than the primary side because of this high current.

For drive transformer this is also step down transformer but in case of drive transformer they are basically used to match impedance.

Here are the list of primary power supply is composed of : 1 Fuse, 1 surge limiter,1 main capacitor,bridge retifier < 4 diode> 1 smps transformer, 2resistors in series ,1 posistor1 ,3 ceramic capacitor, 1 degaussing pin, 1 power pin, many jumper line, 4 signal diode...Secondary output supply is composed of 4
diodes that is carrying a dc voltages taken from smps transformer, filter capacitor ranging to 160v, 100v, 50v,25v,16v and 10v,, right?

Sure Alex, this is a good description of common power supply components found in switch mode power supply (S.M.P.S)

But I have a comment on your remark on the secondary diodes…since the output of any transformer is AC current, that is why we have the secondary output diodes which are used to change(rectify) this AC back to DC current.

The diode only manage to rectify the AC signal into Pulsating Direct Current, this is still not clean enough to be used by the circuits and that is why capacitors comes in handy to smooth this pulsating DC into clean DC ready for use by other circuits.

About horizontal driver series is composed of: 1 driver transformer, 1 driver transistor, driver resistor and the final destination is the HOT Transistor ...Now master my question is where can I find the B+ among the electronics components mentioned above?

The best place get this B+ is at the positive leg of the Capacitor you mentioned earlier rated 160V, whenever you see a capacitor on the circuit and want to guess the voltage on that line it is filtering just consider the working voltage of the capacitor used to filter that line…if it is rated 160V just divide that by 2 and you get 80V…so expect the voltage on the line to be between 80-100, this is just a rough estimate of what to expect thought.

Another good point of getting this B+ is the middle leg (collector) of the HOT transistor.

About R-red, G-green, B-blue cathode pins, at sight , how can we know the RGB cathode pins points? In this regards we need to be accurate pointing pins because the printed layout of all PC board is not the same.

Usually these are labeled like KG, KR, KB and should not be a big issue here Alex.

I am planning to buy a book CRT television repair course thus I am worried1… the pictures you Have shown is not the same with the unit I am for example the picture of pins Fly-back transformer, page 6 of understanding the CRT television critical voltage test points, the B+ is away from the fly-back transformer, it should be the pin of fly-back transformer has a B+. How come the two points has a B+...I am confused...Please show to me the B+ points.

In electronics Alex, what is important is to get the basic concept and then you can apply the same to any other TV model which shows up at your workbench.

Having said that let me say that I have written my book from the technician work bench point of view and you can confirm that from testimonies of satisfied customers who bought this book.

Anyway,,,I am worried to buy a book because it did not show the complete details or picture of B+.

Oh! Alex, this means you status in electronics repair will remain stagnant and this is not a very good report unless you want to change your career to something else.

All the best my friend.

Thank you Master.

Alex Ancheta L.I.B


Thursday, September 4, 2014

introducing a new ebook on LCD and LED television repair

For those of you who are in LCD and LED Television repair and want to sharpen your skills on the same, this book is definitely a good companion on you workbench.

The eBook is written by a renowned LCD's/LED's expert Mr Kent Liew from Malaysia

For more info about the book click the book cover below.

See you on the other side