Friday, August 16, 2019

Troubleshooting dead LCD-LED television


You are sitting in your shop and an LCD/LED television is brought in by the customer, where do you start?
First before the customer leave it is better to connect the television to the power source and confirm what he or she has said.

Also it is important to get a brief history of how the problem developed, this sometimes comes in handy when it comes to diagnosis but please don’t take any advice from the customer when they suggest what they think is the problem They are not professionals and therefore will always lead you to the wrong place.

After you connect the power source, apply the power via the power switch, and observe the power ON led at the front.

1.     Television is dead, Power led is ON.
If the power ON led is red, press the power ON button on the remote control or if you don’t have the remote press the front buttons one by one. One of them will kick start the set if all is well.

If the power ON led is present, this means the television standby voltage is present, the main board is also getting power, and keyboard/IR board is also getting power (3.3 v standby)
Tip
3.3Vdc is used to power the system control unit,
 power ON led, and the IR receiver. This means whenever you see power ON led is on means the standby circuit is okay and the 3.3 Vdc regulator is okay and therefore don’t waste time trying to test them and therefore you should concentrate on other outlets
So even without opening the set you can be sure the standby voltage is okay.

If when you press the power ON button from the remote control and the power ON led does not turn blue means there is something blocking other power to start and therefore you can now open the television and continue with your troubleshooting.

Open the television slowly and carefully because LCD-LED television are fragile not like the CRT televisions especially the screen.

Turn it upside down and use a soft cloth under the screen to avoid scratches. After opening the many screws and removing the cover, do a quick scan of the board component wise looking for any suspicious component like I said before, component with bulged tops are considered bad, burnt marks on components and circuits' board are considered as stress and you should pay close attention to them.

Any suspect components should be subjected to further tests but with capacitors like I said once a capacitor top is swollen even slightly it is considered faulty.


This is because a bulged capacitor is usually short and if you check it with an ESR meter it will read very low ohms and as you know low ESR reading means the capacitor is okay and this will not be true since the meter will be seeing low because of the short and not the actual ESR reading.

With those remarks, it is time to pull your meter and do actual voltage testing, Voltage testing is one of the finest troubleshooting methods because sometimes you may find that the components are all okay but the track/PCB is broken and therefore blocking voltage from reaching other components, also this will help pick any open components quite easily.

Also voltage testing can help you narrow the problem to the affected block

To do voltage testing on the primary side of the S.M.P.S use the main capacitor as your ground (HOT) and for the secondary side of the power supply use the COLD ground (Television body is usually cold ground)


Please note the reason we started with the voltage testing is because we had power ON led lit otherwise if it was full dead symptoms, no signs of power whatever we could have started testing any safety components like fuses open on the board.

Once you clip your meter negative probe on the HOT ground which in our case is the main capacitor negative pin, now it is time to probe every point of interest on the primary side.




Thursday, May 23, 2019

PANASONIC RADIO MODEL RX-CT840 DEAD NOW REPAIRED


A customer brought in this radio and wanted it to be repaired; he estimated the radio to be around 20 years old.


Since the radio was dead the best place to start troubleshooting was the power supply, the radio was using linear transformer to step down the 240 Vac to 9 Vac.

Wednesday, May 1, 2019

21 inch CRT WEGA television take long to power up-screen narrow vertically



I received a message from my neighbor who was not in town to go check out on his television which was reported faulty by his family members since he works out of town.

I passed by in the morning and was shown the television which was left on overnight by the kids but I could see from the screen that the vertical height was collapsed.

The image was narrow vertically; the picture was just 3 inches high.

I inquired how the problem started and they told me the problem started by the television taking too long for the picture to appear on the screen.

Wednesday, April 24, 2019

21 Inch JCV CRT television vertical closed now repaired


A customer brought in a JCV CRT television for repair, kindly note the model is JCV and not JVC and therefore the television can be classified into the cheap China made television which comes with all manner of names.

That is why as a customer you should be careful when buying electronics equipment because many come with names very close to the branded machines (buyers beware).

Monday, April 15, 2019

Sanyo LCD television model 24K40 dead power On LED Red


I received this 24 inch LCD television from a customer who wanted it to be checked.
Symptoms: Television is dead but the power on LED is on and RED in  color like the television is on standby mode.

I tried pressing all front keys and no change, then I decided to open the set for  further testing, once the television was open I scanned the power board with naked eyes looking for any suspicious components  and everything looked good.

VITRON LED TELEVISION MODEL HTC3228 AUDIO PRESENT BUT NO PICTURE NOW REPAIRED



I received this television from my neighbor and the complaint was sound is okay but no picture symptoms.

First I had to confirm if what the client is saying is correct and after switching on the television indeed the symptoms were confirmed right.
I took the set to my workshop and before embarking on opening the set I decided to use a bright light from the torch to see if there is something on the screen like dark picture which will guide me exactly which circuit to suspect even before opening the set.

Wednesday, February 20, 2019

LCD-LED television repair guide

Introducing my new e-book

LCD - LED television repair guide




Dear electronic repairer,

LCD- LED television has been around for some times now and seems like the world trend is geared toward that end.

For the technician this means one need to upgrade his software (studies) so that he/ she is not phased out by the new technology.

I have no doubt the reason you are reading this page is because you want to do software upgrade as far as LCD-LED television repair is concerned...Congratulations my friend!