Friday, July 17, 2015

GIRRO LED TV NO AUDIO PICTURE OKAY

A colleague of mine had a friend who wanted her television checked by a technician and he asked me if I can help her friend sort out the audio problem with her television

I fixed a date and off we went on site with him as my tour guide, I carried with me my usual minimum tools to help me with this assignment.

We found the television ON and the kid was watching the screen although there was no audio and I think this was good enough for a two year kid.

Looking at the screen I noticed the screen had some waves kind of across the screen and I thought to myself…even if I solve the audio problem there is yet another problem with this set and to me this pointed to faulty filter capacitors.

This also led to conclude that maybe if the hypothesis is right and I get faulty capacitor and replace it this could also solve the sound problem assuming that the capacitor also filter the supply to the audio circuit.

I opened the set and scanned around the board looking for any bulged capacitor and I only found a few medium sized capacitors all tested okay to my ESR meter.

The motherboard was too small and I was wondering where is the power supply section, only to realize that actually the TV was using power adapter.



I did not notice when the TV was brought to the table the adapter was left behind. I asked for the power adapter and did voltage testing across the output connector. See the figure below on how to test.


Please note this is not me testing and I just shared this for educational purpose only.

Usually the output is DC and therefore the meter should be set to DC mode, upon testing the output I got a 12.25 Volts and I said YES!...I have got the culprit…the power supply is faulty.

To be sure I decided to confirm if this is the expected output for this adapter and since the TV has no circuit diagram whatsoever, I decided to confirm with the input on the TV body where the adapter is connected and to my surprise It was written 12 volts and that means my hypothesis was wrong and this also gave the power supply a clean bill of health (you can also find the voltage out printed on the adapter body)

With that I decided to change my line of thought and this time decided to check the connection to the speaker and this also seemed okay as far as my eyes were concerned.

I pulled my meter and tested across the speaker connection in circuit and for one speaker I got 6 ohms and I had no problem with that.

Testing the next speaker I noticed it was reading high and kept on changing and I decided to cut one wire to isolate it out of circuit and testing across the two pins I got open circuit.


After that I decided to see the effect on that to the TV and therefore applied the power and to my surprise the audio was back and very clear.

I really don't know what caused the audio to disappear completely after failure of one speaker unless if the other speaker had intermittent problem.
  
That’s all for now guys
Stay safe
Humphrey Kimathi





Tuesday, July 14, 2015

Sinotech CRT television with rainbow screen now repaired

One of my customers from Zimbabwe  Mr.Beau Friend send in an email to me a few days ago....let’s hear what he was up to.....

Greetings Humphrey,
A friend brought in a Sinotech CRT TV for repair - my TV repair experience is fairly limited hence I purchased your recent book to assist me in getting up to speed in this field of repair.
I've sent a picture of the fault - I have a very pretty rainbow effect but not exactly sure where to look for the fault.
I replaced a 1k resistor that had dropped to 270 ohms in the HOT circuitry but still the same - I've thoroughly checked the PCB for cold joints. Any suggestions?
Many thanks and kind regards,
Beau Friend
Zimbabwe
  

Hi friend, first note that resistor can never change value to low... So I suggest you replace the 1k resistor back. Unless if the value went up.
No 2...the problem presented on the screen point to degaussing circuit.
Change the posistor directly and see if there will be change and come back to me.
Finally thanks for buying my book.
Regards Humphrey

Humphrey, you are a star - it was the positor. I've sent pictures of the resistor I removed and the reading I measured on my meter - the resistor color code appears more like 1k rather than 270ohms - what's your thoughts?
Kind regards,
Beau Friend


Congratulations! I suggest you use the original resistor. . That resistor is okay.
Kindly send me the screen shot of the new screen after replacing posistor so that I can write a small article on the same.
Regards Humphrey

Here's the repair results - many, many thanks.
  

This is awesome
Kudos
Humphrey



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