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Aric
Aric, Technician
Category: TV
Satisfied Customers: 33198
Experience:  10+ yrs. experience installing and repairing TVs and A/V systems. Owner of A/V installation and repair business.
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I have a 40" Coby flat panel tv that wont turn on.

Customer Question

I have a 40" Coby flat panel tv that won't turn on.
Submitted: 2 years ago.
Category: TV
Expert:  Aric replied 2 years ago.

How long have you had the set for and when did the problem occur?

Was it after a storm or power outage?

Are there any signs of life at all on the TV (Power light blinking, steady, click sound when power is pressed, etc.)?

Customer: replied 2 years ago.
Answers to your questions:
1. The TV was purchased in February of 2012.
2. No
3. The power light indicator is on and it will dim when trying to turn the unit on, but after about 5 seconds it returns to full brightness again.
Expert:  Aric replied 2 years ago.

Please disconnect the set from AC power, then press and hold the power button on the TV itself (not the remote), for 10 seconds. After another minute, plug the set back in and press power once. Do you still have the same problem?

Customer: replied 2 years ago.
Yes
Expert:  Aric replied 2 years ago.

short inside the set stopping it from fully powering up.

It is most probable that there is a failure on the power supply board inside the TV. Commonly the capacitors on this board will receive a surge and then fail. They can sometimes be visually verified by removing the rear of the set and inspecting them for bulges or leaking fluid at the top or the base of the caps. This is the most common mode of failure for these sets.


Seeing as you are barely into owning the set, you should contact the retailer and you will need to ask them where the closest service location is to have the TV repaired. I wish I had better news, but there are no buttons you can press to fix this and the TV will require service at this stage. If you need further assistance, let me know.

Customer: replied 2 years ago.
Since this tv is beyond the manuf. warranty period. Could I replace the power supply board if there is no visual evidence of damage to the capacitors?
Expert:  Aric replied 2 years ago.
You said the TV was purchased in February of 2012 correct? Do you not have a one year warranty with the set, or was it a refurb?
Customer: replied 2 years ago.
refub only 90 days
Expert:  Aric replied 2 years ago.

That makes sense.

The only power supply for this TV that I could locate, is a refurbished unit as well for sale at the link below:

http://www.ebay.com/itm/Coby-Power-Supply-Board-PC220P-Coby-TFTV4025-/271002709056

Customer: replied 2 years ago.
Thanks for the part lead.

These parts are a "no refund" purchase. I'm not questioning your advise, but what is your confidence level this would fix the problem? Is it a $60 gamble?
Expert:  Aric replied 2 years ago.
I am 99% sure, but if you want to be 100% sure, then you will need to be able to use a meter to measure the voltages coming out of the power supply board. If you require further assistance, please let me know.
Customer: replied 2 years ago.
Ok, if you can tell me what points to check I have a meter.

I have digital pics of the power supply and it looks just like the one you referred to from e-bay.
Expert:  Aric replied 2 years ago.

The first thing you'd want to check is the caps on the power board for bulges or leaking. Any of these needs to be replaced. The Power Supply Board is the one inside the TV that the power cable directly attaches to. Any capacitors on this board that are bulged, or leaking a brownish fluid around them are faulty and could cause the problem you're having.

Please only proceed if you have experience measuring live voltages on a circuit board level.


Next, use a DMM set to DC volts, find a common ground on the power supply and probe all of the Outputs for voltage (correct voltages will be stamped on the power supply at the outputs). Do this with NOTHING connected to the Power supply but AC power, and the small board that has the Power Switch. Turn the power switch on, and then measure the voltages on the Power Supply. If a voltage is missing/ fluctuating, then the power board needs to be replaced.


If the power supply outputs its rated voltages, then connect the other boards one at a time until one causes it to shut down. This board would have the short causing the supply to SOS, and would need to be replaced.


A good source to locate replacement boards is http://www.shopjimmy.com/ and http://www.discountmerchant.com/

Customer: replied 2 years ago.
Ok, I will proceed as directed above.

However, I'm in the eastern time zone, so it maybe tomorrow before I can respond back to you...or are you finished with your advice?

Do I need to accept your answer so you can be paid now? And if I needed to ask you something else concerning this issue are you still available after paying you? How does that work?

Expert:  Aric replied 2 years ago.
I'm in the Eastern Time zone as well, but will be logging off for the night soon. The steps above I gave should be all you need to isolate the problem down to the power supply or another component. If you do need further assistance though, this dialogue will remain open and you can still reply back with questions pertaining to this perticular problem. To do that, you simply need to log onto www.justanswer.com and then click on "My Questions".
Aric, Technician
Category: TV
Satisfied Customers: 33198
Experience: 10+ yrs. experience installing and repairing TVs and A/V systems. Owner of A/V installation and repair business.
Aric and 2 other TV Specialists are ready to help you
Customer: replied 2 years ago.
Here are my findings:

The power supply(PS) board is connected through a wiring harness to the main board(MB) where the a/v inputs and outputs are located. The TV power on switch is 24 volts that is connected through the MB. I was able to isolate the back light(inverter) board only. Does that make sense?

The results were as follows; with AC to the "HOT" side of the PS board I measured the rated voltages on the "COLD" side of the PS board. All voltages are all correct when you initially power on the TV switch, but after a few seconds the power drops out on all outputs of the PS board.

Expert:  Aric replied 2 years ago.

Do all of the outputs drop even with no other boards connected to the power supply board?

Customer: replied 2 years ago.
As I tried to indicate above, (which maybe confusing the way I wrote it), the only circuit board I can isolate is the inverter board. The PS and MB boards have to be connected together in order for the TV power switch to work.
Expert:  Aric replied 2 years ago.
Gotcha. I would replace the supply.
Customer: replied 2 years ago.
Thanks.
Expert:  Aric replied 2 years ago.
You're welcome.

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