Toddo
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Aug 13, 2013, 12:13 AM
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Akai 32" LCD TV Model LCT3285TA - Power Supply
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Akai 32" LCD TV Model LCT3285TA Power Supply
Power supply No. MLT169B
I'm a basic "do it yourselfer". I have no repair technician schooling whatsoever. But, with some detailed guidance, I can do a lot. I have a mulitmeter to check voltages, and I can desolder bad components and solder on new components no problem. I bought this TV at Radio Shack for like $700 around 5 or 6 years ago. Just before the 1 year warranty expired, the TV would not power on. I got the red light only on the face of the TV. So I sent it in for repair under the warranty and what got replaced by the TV repair shop was the component with the yellow oval around it. I have no idea what that component is or how they figured out that was the bad component. So everything worked fine for another year or two and then the TV started powering itself off after being on for like 30 minutes. Turn on the TV and 30 minutes or so later the TV would cut off. So I did a Internet search about the problem and discovered that the power supply probably had bad electrolytic capacitors. Took the TV apart and sure enough, the 6 caps with the red circles around them were ruptured at the top and leaking some crystaline black crap. And the cap with the green circle around it was bulging. So I went to the electronic place and got the 7 replacement caps. The ones with the red circles around them I replaced with higher voltage caps than were orginally installed. Now the cap with the green circle around it, I did not replace because the guy at the electronic place gave me a cap with the wrong temperature rating. All the caps were supposed to be rated at 105 degrees celcius. The guy gave me a cap rated at 85 degrees celcius. And the electronic store was a long way from where I lived so I decided to just go ahead and replace the 6 caps with the red circles around them and left the other bulging one in. So I put the TV back together and to my happy suprise, the TV worked perfect. Ha! Repaired my own TV for about $8 bucks! Well, that lasted a good two years or so until just recently. I started having a problem with the TV not powering on again. The red light would not go to green, or alternately, the red light would go to green but the TV would not come on. I decided to go ahead and get the proper cap to replace the other one that I left in (with the green circle around it) that should have been replaced last time. Now that cap is replaced and I still got the same problem. I got the red light only and the TV would not come on. And yes, I got the polarity of the cap soldered in right.
After doing a search I found this information on the Internet:
http://www.justanswer.com/...9b-power-supply.html
So I then tried to test the power supply with a multimeter. And now I come to my questions that I hope someone will guide me on. So I connected the PSU to the house power supply to test it. Then I pulled all the cables from the connectors in the orange boxes labeled 1,2,3,4,5. I had the mulitimeter set to DC 20. Touched one lead to each of the pins in the connectors and one lead to the TV frame as a ground. I got no voltage at all on ANY of the pins in connectors 1,2,3 or 4. In connector 5, I got like 2.4 to 2.5 volts DC on a couple of those pins. My question is, am I testing the PSU correctly? Do I leave the cables connected to the PSU, then power on the TV with the side panel power button on the side of the TV, then try to make contact with the pins from the tops of the connectors? Because some tiny bit of exposed metal I can see on the individual wires of the cables that I could probably touch the multimeter lead to. Is this a swithed power supply, meaning it has to be switched on with the power button on the TV, which would of course mean the cables would actually have to stay connected to the power supply while I test it? And how bad would it be if when I tested it with the cables disconnected, and with the power hooked up from the house power, and I accidently touched two adjacent pins at the same time with the mulitmeter lead?
So now that I tried to test the power supply, I get nothing at all on the TV. Not even the red light. And the PSU is making a slow light ticking sound when connected to power. Also, my house was built in the 1950's and the outlets do not have a ground. That is to say, no devices in my house are truely grounded. Would that make a difference when testing the PSU with the mulitmeter? I know I must sound dumb as dirt to a lot of you guys. I hope someone has it in their heart to give me some guidance.
(This post was edited by Toddo on Aug 13, 2013, 12:30 AM)
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