Tuesday, June 2, 2015

introducing new eBook CRT television repair case histories vol.2




It is a pleasure to let you know that I have just launched a new book CRT TV Real Life Repair Experience Guide Vol.2

Besides the real case histories included in the e-book I have also added two bonus projects.

1. How to make your own isolation transformer easily
2. How to install universal CRT television kit to any television model


Stay safe

Humphrey

Thursday, April 23, 2015

How to test Horizontal Output Transistor in circuit and out of circuit

One of my customers from Nigeria Mr.Kutelu send in this question to me this morning. for the purposes of those who could be having the same problem i have shared this...

Good day sir. Thanks for your help so far. Pls sir, how can I test Horizontal Output Transistor in circuit and out of circuit so as to know bad one?

Hi Kutelu
Kindly read your eBook page 52/53 for more info on this.


Basically when testing the HOT, first bear in mind all HOT transistors has B-C-E (1.2.3) leg distribution and therefore testing between C and E in circuit expect high and low…


This is because all HOT has in-built diode in them, HOT usually fail by shorting C-E junction and therefore if it is shorted you will find the reading is low both sides(same reading)


If this is the case just solder the transistor out of the circuit and test again between the middle leg(collector) and the emitter(leg on your right side if the transistor marking is facing you) and if you still get low and low(or two reading then the HOT is confirmed fault and should be replaced.


Kindly remember HOT does not just short, you have to find the cause which is making it to short and in most cases the cause is the snubber capacitor.


Other causes of HOT to short you can get more info in your eBook CRT television repair course Chapter 12: H.O.T getting shorted after replacement.
 

Bye and take care.


Regards Humphrey

Friday, February 27, 2015

MARSHAL DVD PLAYER OPEN / CLOSE drawers erratically now repaired



When I plugged the AC cord and push the button of this
DVD player showed On LCD of panel the following ON-OPEN and then CLOSE after this the machine close everything and get off
First I checked the PSU output voltages that were good
The 5 volt output read on my digital volt-meter 4.96 and 12 volt was10.98.
 I found some cold solder joints in the power supply and re-soldered all of them.




Next I opened the disc tray and tested all the mechanical parts plus the three motors were all good.



From experience these kind of problems comes as a result of corrupting the Ware firm of this machine( flash EEPROM EN25F80)
This is a  8 Megabit Serial Flash Memory With 4Kbytes Uniform Sector




Fortunately this I.C was not SMD form and good manufacturer installed this I.C in Socket
This is another reason that this I.C must need re-programming once a while.
By the help of original program and I.C programmer I Reinstalled the FLASH EEPROM and the machine started working as new.

NOTE: FOLLOWING LINK  ALSO GIVE INFORMATIONS ABOUT TNM IC PROGRAMER 

http://www.ebay.com/itm/TNM-2000-USB-MINI-Universal-Programmer-TSOP32-TSOP40-TSOP48-NAND-Flash-adapters-/321207236799

The article was brought to you Mr Beh.
Electronics repairer based in Tehran-Iran.

Want to improve you skills in DVD player repair? click on the book cover for more info.



Thursday, February 26, 2015

customer support-Ryan all the way from Philippines

Ryan Atong from Philippines send in a few questions on CRT television repair course

Thank you for the books.....I’ve started reading it already and got some few questions ...I’m gathering it. .so I just email it to you one time…

Thank you Teacher

Okay, no problem Ryan

Hi Humphrey, I have few questions upon reading the book

1. The snubber capacitor (is it snubber caps by the way) which is
rated 400v...

This is not snubber Ryan, it is called S-correction capacitor, all snubbers are rated between 1200volts-2000volts.

 Is there any effect on the HOT in case they got faulty?

S-capacitor fault? NO effect on HOT, but if S-capacitor open there will be a single vertical line on the screen.

Sometimes the television may go into shutdown for safety purposes, it is a serious problem and therefore don’t put the television on with this kind of problem because it can cause more damages.

Also if S-capacitor shorts it will load down the horizontal supply and this can cause the television not to start.
Read page 66 and 67 for more info on this.


2. How can I measure the voltage of the new replace snubber capacitor? Can I just put 2 probes on the caps? It AC right. Because snubber caps has no polarity?

As you have noticed from your book, Snubbers have one leg on the middle leg (collector) of the H.O.T and the other leg on the emitter (GND), therefore if you test the Voltage at the middle leg of the HOT you are actually sitting on the snubber leg, if the horizontal circuit is not working then you will get the B+ voltage at that point.

The B+ is Direct current(Dc) and therefore your meter should be in DC range, as you know capacitor block DC and pass AC and therefore the snubber capacitor has no effect on this DC voltage, now if the horizontal output is working( this you can tell by watching the screen) as in if there is something on the screen it is assumed that the HOT/snubber/flyback is working and should not be considered for any troubleshooting…in fact it is not allowed to test the voltage at the collector of the HOT if there is something on the screen, you can even destroy the meter instantly

3. If I change the snubbers and the driver transistor and still the
HOT become shorted I have to change already the FBT...but do i still
change again the snubbers and the transistor or just FBT alone.

Not a must but it is good to confirm if they are okay or not

4. How do I know the snubber is short or open?

For short just use any meter set to low ohms, if you get any reading even at the highest range then it is considered the snubber is shorted. If open you cannot tell with a meter because usually a good snubber capacitor test open using any meter. Here the best is substitution. But again as I said if the HOT tested okay, that is good enough test that the snubber is also okay.(NB if the snubber goes it will go with HOT)

Cause i went to the market to buy these capacitors and i broguth my FBT for testing
also...as for my surprise, the FBT is breaking down when loaded.so i conclude that the reason why
the HOT get shorted is because of the FBT.

Could be, though this is not clear to me.

5. How can I test the degaussing coil? Is it continuity, cause in your
book I see 2 reading, 1 is 13.3 and the other is 0.12. by the way I am using auto range digital multi-meter

You can use your meter set to low ohm, as you have rightly put it expect low ohms, the example I used in my book is 13.3 ohms and the other was 12 ohms but not 0.12 ohms, kindly consider  12 ohms and 13 ohms.

If you get infinite reading then the degaussing coil is considered open and therefore faulty..

Finally the best test for degaussing coils is fly back tester

Thank you Humphrey..

Ryan

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.

Note:
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
Nigeria


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.

  

Advice:
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