Philips Television 14” with intermittent problem-email support

I received an email from one of my recent customer of CRT television repair course from Zimbabwe Mr U Nhende, lets hear what he has to say:

Customer from Ghana defies all odd to have CRT television repair course on his workbench

One of my latest customer from Ghana Mr Aboagye Kwasi defied all the odds to have CRT Television repair course on his work bench, it all started when he inquired from me other options of paying for the book apart from PayPal which is not covered in Ghana.

Telefunken TV with colored spots on the screen

 Thulani: How are you sir? I have encountered a problem with a Telefunken TV, l think the problem is on RGB circuit, the picture is there, it shows three colors which is red on the four corners, blue and green on the center screen. When l check the main RGB volts 200v and on board is 180v.the RGB is from FBT

Question about fly back tester

I have received several emails from technicians who use fly back tester to test the fly back and get good results but still the fly back is faulty, listen to this conversation between me and Mr. Daud Asi from Pakistan.

Diode Tutorial & How to build an AC to DC power supply

SATELLITE RECEIVERS, STRONG SRT 4650 DEAD.

Hello Mr Kimathi.

Amos: I hope you are fine with your daily activities, am fine too. I am receiving now days dead satellite receivers, with many problems, I can only solve small problem like burnt fuse, diode, transistors but it is difficult to repair them because I don’t have enough knowledge about it. All receivers use switch mode power supply, many of these power supplies die, and all these trouble model come from China. How can you help me how to deal with satellite receives, many peoples in my area have

How to make your own pcb

Hum-tech electronics takes a short break

This is to inform my fellow technicians and friends that I will be taking a short break to travel upcountry some 230 Kilometers from Nairobi to give my Dad last respect who passed on this Morning at around 1.30 am.

For that cause I will not be able to respond to email till end of next week 19/11/2011, in the meantime the blog is online 24/7 and hence you can always search for any info you are looking for within the blog and you may be lucky to get the answer because most of my articles are based on what most techs ask and therefore you may find another tech had the same problem and is answered on this blog.

God bless you all

Regards Humphrey for hum-tech electronics

Electronics Graduate asks for the best way forward after graduating as electronics technician

Hi Humphrey,

I was on Internet looking for something regarding Electronic field and I found your blog, I'm Haitian living in USA in Florida, so I would like to get in touch with you because I just graduated in this field, as technician in electronic I would like to know the best thing in practice.

Customer support-via email between me and a customer from Philippines

 

Good day Sir,

                   I like the book. it made my mind open in terms of CRT Tv repairing which my former lecturer in basic electronic course did not even gave us a single technique like you did. Thank you so much.

Customer support-via email between me and a customer from Philippines

Randy: Our television Toshiba 21 inches, picture is stretched on top of the screen with thin white lines.

Humphrey: I can’t get your point maybe you can send me the picture of the same.

New electronics repair blog

 A friend of mine and a fellow technician from Belize Mr Jorge Manzanero has started a repair blog and for more info kindly click on the picture below…

Customer support-via email between me and a customer from Belize part 2

Jorges : I had already disconnected the collector from board, and the snubber and diode that goes to pin 1 of fly back and still there is short to that pin from ground. Sir this is hard. Do you think maybe I go check elsewhere else, or is it time to do voltage testing...although there is short?

      

Customer support-via email between me and a customer from Belize

Hello Mr. Humphrey,

Since studying your eBook, I am now working on a second TV. This one is for my Boss and is a Precision PTV 29R89S with Chassis TMP8823CPNG5VAH. However sadly I can't find the schematic nor the pin out of the flyback.

Customer support-via email between me and a customer from Florida (USA)

Hello there Mr. Humphrey!

This is Gill from Coconut Creek, Florida (USA).

I just bought your book a few moments ago, and I’m enjoying reading it.

On chapter two you mention, that inductors allow low frequency to pass, and make it very hard for high frequencies to pass; and that capacitors allow high frequencies to pass but make very hard for low frequencies to pass.

Customer support-via email between me and a customer from Belize

One of my latest customer Mr. Jorge from Belize send an email to me with an issue which he wanted me to explain a little, let hear what he is saying.

Hello Mr. Humphrey,

Please just one question on the CRT course that I am not sure about. 

1.   I reached chapter 9 “on how to find a shorted components using series bulb on the primary power supply fast!”… Where it says you remove a pin of some components. When I do this, do I re-solder back a component if it is ok and go to another or do I leave the pin out and go take out the pin of another?   

Sanyo color 21” model AMV-2136 Dead -Customer Support via email

Here is a small email I got from one of my CRT Television repair course customer.

Good day my friend,

i have a customer with Sanyo color  21"  model AMV-2136 ...

Problem: Dead on arrival

Remedy: After opening the Equipment. Fuse is totally black (blown)

      

The story of Steve Jobs, founder Apple..in his own words

 “Do you want to sell sugar water for the rest of your life or do you want to come with me and change the world?” quote by Steve Jobs as he tried to woo Pepsi Executive John Sculley to join Apple as president and chief executive officer in 1983.

NEC TV 21” CRT sound not ok but picture Okay

 This TV was brought in my shop with the picture ok but the sound was not stable…sometimes good and other times not.

I opened the set and went straight to the speaker (power off and power cable disconnected from the power outlet).

Feedback from a blog visitor

 In electronics we usually encounter feedback circuit; the purpose of feedback circuit is basically to couple a sample of the output signal back to the input of the circuit. This signal is analyzed and compared with what is expected.

If the sampled signal(Voltage) is less the expected then the control circuit will cause the switch(e.g.transistor) to move faster in order to increase the output monitored source and vice versa

In real life scenario feedback is also very important, for example as a blogger it is very important for the followers to take some time once in a while to let the host know if what we are giving is high or low value contents.

This will guide us to respond accordingly and in doing so improve on what need to be improved and suppress what is not relevant to you as consumers…one of the best way to let us know how we are fairing as bloggers is by dropping a line or two on the comments box.

Blogging is generally a very social community and therefore those who are active in it often get recognized and this can lead to more visitors to your blog or even more opportunities may come knocking your doors.

 Below you can see a comment dropped by a Mr. JG Manza after reading this article on Akira Television dead.

http://humphreykimathi.blogspot.com/2011/03/akira-television-dead.html

Another very important form of feedback is Guest posting, once in a while consider writing an article for other websites and by so doing you will get an idea of the quality of your content if you are getting started in this road of electronics.

I never knew I am good at writing electronics articles until the time I was given an opportunity by Mr Jestine Yong of Best electronics articles to write an article in his monthly electronics repair newsletter and from the feedback I got from the readers really gave me more confidence to move on writing more and more, eventually I wrote my first eBook on CRT television repaircourse.

All the best guys

See you on the other side.

Plastic soda bottle used as source of light

Recommended by Mr. Beh... thanks Mr. Beh

Akira Television 21 Inch dead

Roger: sir good day,,,,now I’m repairing a 21 inch,tv,akira,,,,the power regulator ic is down,,,so i replace,,,,there is also a ceramic disc cap rated 222k is burnt already at secondary side, beside output diode, so i replace,,,by the way the fuse have burnt also,,,,so i power the set using light bulb,,,when i plug i noticed the front led not lighted,,,,, what the area I’m going to check sir,,,maybe the micro not power also,bcos,,no 5volts,,,,, by the way this tv is using power ic,,,str g6653,,,even there is no 5volts ,I try to sw.on the set,,and i can do voltage testing,,,the main cap is 300v,,,pin 1 of ic is 300v also,,,,pin4 is about 14to 16v,,,,pls,advise me sir,,thanks,,roger

Humphrey: Any voltage on the secondary side of the power supply?

Roger: sir, good day,,,i continue checking at primary side, I bump to a resistor rated .15 ohms,,,its reads 18k ohms,,,so i check the link of this low ohms resistor,,,it connected to pin 2 of str g6653,,,it is a current sense resistor,,,that turn to high ohms,,,i think this is cause why the power supply and also front led not functioning,,,,,am i correct sir?,,,now im preparing to install a new low ohms resistor,,rated 0.47ohms,,,,,because    0.15-ohms is not available,,,,maybe this tv is start working,,,,after i replace total of 5 components,,,,,,by the way sir thanks,,,,,,i let you know ,after i fix this tv,,,,god bless,,,roger

Humphrey: 0.47 ohms is still quite high for current sense resistor...use three 0.47 ohms resistors connected in parallel to get 0.16 ohms for this circuit.

 Roger: ok,sir ill do that your good advise,,,,i will make 3 ,,,,,,,0.47ohms resistor in parallel,,,,thanks

Roger: sir good day,,,,after i replace a e-caps at the vcc rail of str g6653,,,when i sw.on the front led has come on now,,,,but i notice the light bulb is having intense light,,,,so i check the voltage at the secondary diodes,,,all are ok,,,but the B-positive is low,,,i disconnect the degauss coil,,,,check again the voltage at B-positive its reads 112v,,,so i confirm the posistor is already short,,,,Because  i check the degauss coil is ok,,,,now,,,all the voltage output at secondary is present,,,,but the tv does not sw.on,,,,,the front led is ok also,,,,,the micro is already powered,,,,but why the tv cant sw.on ?   so i check the condition of fbt,,,primary winding is ok,,,,i powered again the set and check the fbt secondary voltages,,,the 185v reads only 112v,,,,,,the screen voltages reads 3.2v,,,,,the other fbt output no readout,,,,,so why this happen sir think the fbt is already gone also sir? Even though the primary winding of fbt is ok? You know sir? I learn a lot in this trouble-shooting,,,pls.advise me sir,,thanks,,roger

               

Humphrey: I don’t think the fly back has a problem, I suspect the horizontal drive circuit, read your book chap 10 for more details on testing and troubleshooting this circuit.

The Voltage of 112volts at the output of the FBT is same as the 112volts b+ voltage because the fly back is not switching. So this leads us to suspect a problem with the drive circuit. For example any voltage at the collector of the drive transistor? How much?

Check that and come back to me please.

Roger: sir good day,,,,,yes is true that the output voltages the same,,,,,,112v,,,,now my mind is thinking so much,,,,I  have read again the book at chapter 10,,,,,i think my assumption is correct,,,to double check the horizontal drive circuit,,,,,,so i confirm to you sir about your advise,,,,,,sir you know you’re a nice guru for me,,,,,so i study hard for this field,,,,,especially CRT TV repair,,,,,big thanks for your advise sir,,,,,i let you what the progress of repair

               

Roger: sir good day,,, I check the horizontal drive circuit,,,,i power on the tv,,and test the voltage at collector of h-drive transistor it reads 112v,i trace the line is coming from the b-positive line,,,pass the two 10k resistor in parallel,,,,i check the pulses at the base ,,i find dry joints,,,,so i re-solder the area of h-drive and the pulses is ok,,, ,,,,now the set is totally power on,,,,sir you know I have so much learn about your advises for me,,,,i have so many things in trouble shooting that i have learn,,,,dos and don't,,,,procedures,,,the principles that I learn in your book is giving me a inspiration to continue learning this field,,,now my confidence is simply increasing,,,,,b-cous of your support sir,,,,

Leader pattern generator (model LCG 398-B) repaired

Recently during some test on a CRT Television I found out my pattern generator is not working after many years of service. The switches on the panel were broken and also no signal was coming out of the equipment.

I opened up the machine and upon keep observation I noticed numerous dry joint and I re-soldered them and also replaced the broken keys and the machine came back to life.

This report is brought to you by Mr. Beh.

An electronics repairer based at Tehran in Iran

If you want to learn about this equipment and what it’s capable of doing click on the like below

signal generator

How to make up any value of resistor for replacement if you can’t get the exact value

On your line of duty as a technician in electronics sometimes you may come across a resistor burnt or has changed its original value and being one of the cheapest component in the market you visit your nearest electronics shop but alas, they can’t get the exact resistor value you are looking for.

I have in mind the example of the current sense resistor which is found in almost all switch mode power supply. Current sense resistors are usually low ohm and very precise and therefore a small change in its original value (usually upwards) can cause the whole power supply to appear dead.

In this lesson I am going to talk a bit on how you can make up any value of resistor you need for replacement in case you can’t get the exact value. In order to accomplish this mission we are going to use some characteristic of resistors when connected in series and in parallel.

If resistors are connected in series then their individual resistance are added together to get the total resistance. See picture below.

If resistors are connected in parallel their total resistance is always less than the smallest resistor value in the association. In the example below we have two one(1 Ohm) resistors in parallel. If the resistance value is the same in parallel association then the formula is simple. Just divide the value of one resistor by the number of resistors.

From the above picture we have the value of the resistor is One(1 Ohm), to get the total value of resistance in parallel just divide the 1 ohm by the number of resistors two(2) and the value is ½ or 0.5 ohms.

As you can see the total resistance value is less than the smallest value resistor (in our case one (1 ohm). Therefore if you wanted to get half ohm resistor there you are.

So next time you encounter problem of getting a certain resistor value now you know how to go round this problem.

All the best Guys

See you in the next class

Hum-Tech electronics one year Anniversary

 A quick view of my profile shows on user statistics that I have been a blogger since August 2010, That is exactly one year since I joined the world of blogging, and as we celebrate our first birth day here at Hum-tech electronics I wish to thank each one of you my dear friends and fellow technicians out there for your contributions,comments,feedback and words of encouragement..

As we share this birth day cake please allow me to call to your remembrance an African  proverb which says “ if you want to go fast, go alone.If you want to go far, Go together”, as technicians I think we can borrow a leaf from this saying….lets walk as a term GUYS……..

Wishing you all the best

Humphrey Kimathi

Never despite a humble beginning

Click to read more.......

A Satisfied Customer Comes Back!!

 I received this email from one of my CRT Television repair course book Customer from Tanzania, and I was getting ready to find out where he needs my support in relation to his day to day repair works.

But as I continued reading down the email I realized this is a Satisfied customer who is coming back but this time not for any assistance as far his repair work is concerned but on how to add some flavors to his repair work by enjoying some of his favorites soft music in the background as he continue to enjoy his repair work.

Here is the Mail…..

I remember Amosi is one of my very first customers to buy my eBook, He came to me a few times at the early beginning and of late I have not heard from him but now I know why(The backlog is gone and his work bench is now cleared). So I expect very fast service delivery to his current customers. This will also definitely translate to increase in profit.

By the way dear Techs if you find your shop has many equipment laying on your shelves does not mean that your business is doing well….It could mean you are taking too long to diagnose and repair hence the backlog.

And if you are not careful you will find your shop full of equipment and you will have no room left even for you to sit comfortably. This will increase your stress levels and soon you find your output going down even more.

Another thing worthy to note is that in Tanzania English is not their First language but despite that Amosi seems to have read my book and understood it pretty well because I have written it in very simple English and numerous color photos to make the reader understand very easily.

Here is a clip by Emmy Kosgei.

Wishing you all happy repairing

Humphrey Kimathi

Author CRT television repair course

Mobile phone repair tips

 

Sometimes on your line of duty as a technician you may encounter a customer who brings to your shop equipment which maybe you don’t repair but insist that you check for them what could be wrong with their equipment.

Although I am not very experienced on mobile phone repair I usually get some customers who bring their phone to me for repair and usually if the problem is hardware related I undertake to repair it.

Mobile phone problem are frequently hardware related and if you are keen one can be able to make conclusions as to the faulty component even before opening the phone by listening to the customer complain.

Here is an example.

1.       Customer complain:

When I place a call the phone does not indicate when the phone has gone through. Only hear the other party if the phone is set to loudspeaker.

Check the ear piece with analogue/digital meter set in low resistance range. Should be around 30 ohm when okay.

Solution: Usually changing the earpiece (speaker) cures this kind of a problem.

2.       Customer complain:

 I can’t hear the other person. In that case when the phone is dialed the phone rings and when you receive the call. You can’t hear the other person.

Solution: ear piece fault see above. Again one can use loudspeaker if the phone is equipped with one.

Nb: remember the ear piece could be okay but there could be other factors which could be hindering it from functioning. Be very keen to do observations around the ear piece, gasket, connector parts, the housing itself. - is it completely closed (home). Any loose bolts or missing bolts which could make the ear piece not to connect fully to the circuit board? Also check the orientation of the ear piece in connection to the main board.

Note: The earpiece and buzzer (ringer) are different. Some mobile phone has earpiece and loudspeaker- in this case the loudspeaker is used also as buzzer (Polyphonic Ring Tones)

3.       Customer complain:

When I make a call the other person can’t hear me but I hear them

Solution: Check the microphone (mouth piece) is loose or faulty-usually replacing the mouthpiece cure this kind of problem.

4.       Customer complain:

The phone goes off often, switch on and off after a small shake.

Cause: battery bad or shorted or battery connector loose.

Solution: change the battery/ Check the battery connector is firm.

Tip: Dust is one of the main killer of electronic gadgets and mobile phones is not excepted and therefore before you start suspecting component failure on mobile phone please be sure to do thorough cleaning of the PCB board with medicinal spirits and dry the board well with hair blower or hot air (this usually solve 30% of mobile phone problems)

That’s all for today guys

See you in our next class

REPAIR TV REPORT PARS GRUNDIG 21" COLOR TV PART –Dead part2

In the first part of this repair report by Mr. Beh, he promised to come back with his final report of what he did next to the Grundig 21” Tv which refused to have high voltage even after replacing the fly back with a new one.

No doubt Mr. Beh is back with his final report on this repair …

Mr. Beh tells us we are listening…….. After I changed the fbt of this Television with a new one I expected the Tv to start working but the TV did not work and therefore I did not have high voltage yet.
 

This TV has an ic on the drive circuit and I decided to Google it and see what is it all about, the reference of this ic was TDA8140, after searching the net for this ic this is what I got.

The TDA 8140 is a monolithic integrated circuit designed to drive the horizontal deflection power transistor। And here is the application circuit for the same.

From the datasheet above you can see no doubt this is a very important component as far as horizontal deflection circuit is concerned because it is actually the driver circuit.

So I decided to change it and this time the TV has high voltage and I was happy but wait a moment, the picture came up but with a vertical line at the middle.

I started testing components on the same circuit and I found an electro cap in same circuit which was not good according to my meter and after replacing it the white line disappeared.

The Television is now happy and ready for collection by the customer.

Thank you guys.

God bless You

By Mr. Beh.... An Electronics repairer based at Tehran in Iran. 

REPAIR REPORT OF PARS GRUNDIG COLOR TV 21” MODEL 5593-DEAD

This article is brought to you by Mr. Beh. An Electronics repairer based at Tehran in Iran.

Initial facts:

The estimated age of this Television is around 12 years of continuous service, No circuit found over the internet.

First I have to tell this TV set was rejected by authorized repair center and brought to me Completely dead with no sign of life, After blowing the inside I checked the Big capacitor by analogue meter set on dc mode 300 v dc

My voltmeter confirms that the 300 volt dc is reaching to the pin of the main capacitor (The red probe to the Positive side of capacitor and black probe to the negative side of the BIG filter cap).

With this I concluded that that all components before the main capacitor like bridge rectifier on /off switch, AC cord are ok and therefore not considered for any further testing.

I checked pin no 6 of regulator ic this is TDA4605 ( by goggling I found the diagram of the ic and the Vcc of this ic that was pin no 6) the red probe of the meter was on the pin 6 and the black probe the negative pin of the Big filter capacitor.

My meter read nothing. Zero volts. Checking the pins of this ic and all surrounding component I found out that there were many cold joints in the low power supply area. I took time and re- soldered them all again.

After that I powered the set and checked pin no 6 of regulator ic and Yes! I got about 11 v dc in V cc pin of ic and is within tolerance. This means the set is getting all the important voltages but to my surprise still TV has no sign of life.

Then is decided to check the secondary side of smps. With my analogue meter I checked the voltages coming out of the smps. This TV has 5V output from the transformer and 5V Schottky diodes, by putting the red probe to the negative (Cathode) side of diodes and black probe to cold ground of the Television.

I checked them all one by one, the voltages were within tolerance and are ok and I was happy up to here. In old CRT TV, usually there are two components that bring problems.

1 HORIZONTAL OUT PUT TRANSISOR (H.O.T)

2 FLY BACK TRANSFORMERS

First I checked the H.O.T by putting my meter on ohm mode x10k (H.O.T in this set is BU508D). D means a diode also is installed in the transistor compartment

And the shape of pins from left to right when the face of transistor is up is B.C. E .And by comparing the reading of meter with new healthy transistor I put ok stamp on this H.O.T of this TV. But what else can cause this problem? The only card remaining is now the fly back transformer?

To test the fly back I used my home made fly back tester which was on my work bench, I checked the pins of this transformer comparing with a good fbt and I concluded that trans former(FBT) is not ok because checker showed two L.E.D were lighted.

Below you can see assembled homemade fly back transformer and expected result from a good fly back transformer (all L.E.Ds) are ON.

I changed with one I had in my salvage stock, After replacing the fly back still there was no high voltage ?...having used my last card I took a break…

See you on the next and last part of this intriguing repair experience

God bless all repairer

Beh

Testing integrated circuit (i.c)

I have received several emails from techs who come to me for some guidance in relation to at what point should one suspect an ic is faulty. In this article I wish to shed some light on this issue in relation to CRT television. (Of course you can use the same knowledge in other equipment using ics) 

In CRT Television we have several ics like Audio I.C, Vertical ic, RGB amplifier ic, control ic in the power supply and lastly the jungle and micro processor ic.

The latter ics are quite expensive and therefore it is very important to very sure that indeed it is the ic which is faulty and not related components causing the problem. 

The word integrated in Basic English means included there in. Such as active components like transistors and passive components like resistors, capacitors in order for it to function.

So in I.C like the micro processor or jungle ic expect many components both active and passive which form circuit with different functions within that particular ic.

So one clue that an ic is bad is function failure, Take for example the micro processor part of the circuit which produces tuning pulses for channel selection in CRT television. If this particular circuit fails then you will find the TV is not able to do channel auto searching.

If you get this symptom and you find the entire external component associated with turning are OK, then you can conclude that the micro has failed partially because you will find sometimes other functions of the micro will be okay.

If you find NO function of the micro is working, then first check if the micro is getting power. Power supply is very important for any ic/circuit to work and therefore should always be checked to see if it is present and correct value.

Another common occurrence on these ic is actually dry joints on the components around it and also actual ic pins.

Sometimes a technician can change the whole ic when actually the problem was dry joints. So when you replace the ic its like you have re-soldered and hence if the TV work you will imagine that actually it was the ic faults while it was just dry joints problem.

This will waste your time and also lower your profit margin, from my experience I have seen these main ic(the micro and jungle ic) are quite reliable and highly protected from static discharge and power surges and therefore should be last on your suspect lists.

Below you can see a diagram of a TV micro, before you replace it consider checking the fuses around this ic, you never know they were fast enough to open to protect the micro and changing only one of them can cure the problem.

Tip

One good symptom of a bad ic is that they usually get HOT and also the VCC voltage goes down(Nb you expect 5 volts but you are getting 2volts
 

To learn more on how to troubleshoot and repair CRT television like a professional click the link below…

CRT Television repair course

Wishing you all the best

Humphrey Kimathi

Author CRT Television repair course

Meet Rose Nasimiyu-A 9 year old cancer survivor from Kenya

Meet Rose Nasimiyu, a nine year old Girl cancer survivor tell her story….

More videos as she continue to encourage others with the same condition…

Understanding the x-ray protection circuit in Television

High Voltage shutdown commonly referred to as X-Ray protection circuit shut down the horizontal deflection in the event of a detected faults if that faults causes CRT radiations to exceed acceptable limits.

It is important to note here that HV can increase even if the power supply is okay; a good example is if the safety capacitor (snubber) opens or looses some of its original capacitance.

If any of the above faults occurs in Television, It will cause the Fly back to produce undesirably high secondary voltages. The good news is that as the HV increases all other output from the fly back also increases and therefore this circuit of X-ray protection is not attached to the HV output which could have caused more challenges to the designers but another output of low voltage is monitored.

Usually a voltage reference is taken from the FBT and rectified by a diode to get a DC voltage, this DC voltage is applied to a precision resistor divider, the values of these resistors are chosen to produce correct X-Ray protection trip threshold for each CRT.

Below you can see a simple X-ray protection circuit usually found in CRT Televisions.

If the voltage increases above normal (say 13 Volts) the Zener diode which in our case is a 12 Volts Zener will conduct and voltage will appear at the X-ray in pin. The X-ray protection pin is usually zero volts when things are normal and if this pin get voltage, the I.C internal shutdown circuit will trigger and shut the horizontal out signal and hence shutdown the Television.

This will then prevent dangerous X-ray being emitted which could have otherwise caused health hazard to the user or even break the CRT tube.

Conclusion

I think now you can see why you should never replace the safety capacitor with one with lower capacitance value because this will cause the HV to increase a lot and hence emit this dangerous X-ray radiation.

One sign that the snubber capacitor has lost some of its original capacitance is that the screen usually become narrow (E/W) and sometimes you can even hear cracking sound caused by this excess HV. When you get these symptoms this is an indicator that this capacitor has lost some of its original capacitance and replacing it usually cures the problem.

Wishing you all the best

Humphrey Kimathi

Author CRT Television Repair course

Homemade ESR meter assembled n working

Roger:  what is the purpose of 100k potentiometer in your ESR diagram? what will be the settings, for now I started to assemble the ESR  tester… it’s almost done…the IC TL062 or TL072 is lacking,,,  it’s hard to find the ic…but I’ll try other electronics stores …

Humphrey: The 100K pot is like the zero adjusts of your analogue meter. So it will be used to adjust to zero when using the esr meter attached to your analogue meter. Please try and get any of these two ic...they are very cheap in the market.

Roger:  sir, good day…I finish assembling the esr…but when I switch ON, only little flick…when I short the two leads at the esr… no movement…I used ceramic disc caps,,102m,,,104m,,, is this right sir? I check the vcc pin of ic TL062,pin 8 there is 5 volt there, but I wondering why that no movement or not functioning…I check also the ic pins 5-6-7-8,,jumper,,pls,advise me sir...thanks

Humphrey: That little flicker is ok...now try to turn the P.O.T knob all the way with the  two probes shorted together and see if it goes to zero and come back to me. The 102 and 104 are ok..best of luck.

Roger:  Sir, I try your advise no effect even though I adjust the pot 100k ohms…

Humphrey: Let me have the picture of your assembled circuit both bottom and components side (main esr circuit only)

Humphrey: your pictures are not clear but I am able to pick some few things...

1. Did you cut the 4 track on the underside of the ic 4 pins...i can’t see them.

If they are not that means the ic is doing nothing because it is just shorted on the 4 pins...

2. I can’t see the jumper wire from pin 8 of the ic to 100 K resistor.

3. I see jumpers on the underside what are they doing there.

Finally let me say this…This circuit which I reproduced here is the one I used to make mine and I have not added or subtracted anything and so it should work.

Please note my template is the road map. You should follow it the way it is...


Please if you think you have not followed the template to the letter you can start again because i see the ic is on socket and therefore you can always re-use it...

Again after assembly you will get something like the one I have done because I used the same template to do mine.

Roger:  Good news sir, the esr is working now…I analyzed what you have advised…I think I mislead the jumper at the bottom of ic…, when I looked at the diagram…so I immediately cut the jumper at pins 5,6,7,8,,,is shorted….after that i test its viola sir….thanks for your support sir, I really appreciate…God bless you…,now I can practice testing bad caps……

Compiled  by  Humphrey Kimathi

Author CRT Television repair course

GLD Television with a single horizontal line

This Television belong to a Colleague of mine, She has a phone which she wanted me to check for her which was having some problems and in the course of our chat she told me that she also has a TV which is lying in her house and if I know a good technician who can look at it.

I asked her what does she mean by a good technician and told me she no longer have trust with technicians because of previous experiences with them…I did not like to go into details of her past experiences with techs and therefore I offered myself as a possible option if she wouldn’t mind.

She agreed but the condition was that I must repair it on site, I requested her, the possibility of me taking the motherboard alone with me for troubleshooting and repair in my workshop and come back to her to re-assemble the set in her house.

That option also didn’t work and therefore having no other option left for me, I decided to do it on-site (while – She - wait). Besides from the description she gave, I knew it is not a major assignment as you know with single horizontal line on the screen that directly point to a problem on the vertical circuit.

So I gave her an appointment for the following day after work, in preparation for the day I took a small digital meter(the eyes of the technician), a screw driver, half feet long solder wire, solder gun, solder sucker and a side cutter and placed them in my on site traveling bag.

Also because from my experience with these China made TVs I carried with me some two Capacitor rated 1000uF/35v and 470uF/35v. Both capacitors filter the vertical supply power and they have a very high failure rate.

Come the appointment day and I went to her place ready for the task ahead. The television was brought on the dining table which for now was to serve as my repair work bench.

As usual I had first to power the TV on to confirm what she told me and also to get any other clue from the screen itself. After powering on, the TV came up and indeed there was a horizontal line across the TV screen.

Looking at the line keenly I could see the line was not smooth but had some waves like on the sides. This could points to dry joints or loose connections around the vertical circuit. I tapped the Television softly with my bare hands and the line (horizontal kept on changing) which further indicated the possibility of dry joints.

I opened the set and did some scanning on the secondary side of the power supply on the component side and I didn’t see any suspicious component, then I turned the board to the bottom side and went straight to the vertical ic (LA 78040)

 

Without magnifying glass I could see two big dry joints (I mean like pot holes on pin 2 and 6 of this I.C LA78040) below is the datasheet of this ic.

Looking at the datasheet above you can see pin 2 and 6 supply this ic with the much needed 27 Volts supply from the secondary of the power supply. 

The 27 volts goes through a diode and it is split into two, one line goes straight to pin 2 and the other goes to pin 6 always through a diode and therefore expect a small drop across this diode of about 0.7 volts (so the voltage at these two pins will be almost equal (+ or –) 0.7 Volts of each other.

After re soldering all suspect areas it now time to power up…usually after repair I like powering the set via series limiter bulb but because I never carried it to the site I had to do it directly.

I pressed the power ON button and nothing happened. Even the horizontal line is not there…DEAD. I tried to listen to the signs of life from the TV and I could hear some sound from the secondary side of the television.

What could have happened now? I figured out that because this TV was having a horizontal line before and now it’s not powering on it could mean that there is something I have done wrongly in the course of this repair…and the most probable thing could be while I was Re-soldering the dry joints I could have shorted a components pins or path because the light was not enough to see the solder are perfect.

So without the magnifying glass I used my meter set to continuity range to try to locate the shorting path/component pins. There was a connector I had re soldered and I went straight there to confirm if it was ok. After testing the two pins I could hear the meter beep (the connector had three pins and all the three had beep)

After further investigation if noticed this is connector for 180 volts RGB supply, heater voltage and heater ground. The heater pin and ground should have a beep but not for the 180 volts. So did some cutting between the heater supply pin and the 180 volts supply until I heard no more beep.

Again I powered the TV and this time the TV didn’t disappoint me…it came up nicely.

A word of advice to new technicians.

I would not advice you to repair equipment at the owner place unless you are very confident with yourself. 

You can easily forget and discharge one of those BIG electrolytic capacitor with a screw driver and with the sounds it makes and the sparks generated you might find everybody running out of the house with the fire alarm already activated for fire fighters to come in to put the fire out which they perceive you have caused.

Wishing you all happy repairing.

Humphrey Kimathi

Author CRT Television repair course