Question about Akai LCT2785TA 27 in. LCD Television
to all from Tom Arnold, WA6OVP
Subject: Repair of computer monitors or flat panel TV’s.
Recently my wife's 27-inch AKAI (LCT21AS) 27-inch flat panel HDTV with DVD player quit working. Years ago, when I had an analog computer monitor quit operating; Joe Fadden WA6DDF had mentioned to me, that often computer monitor problems were caused by the monitor's power supply. Joe also said these power supply problems were often caused by failed electrolytic capacitors. Joe said he was able to fix many computer monitors by just changing all of the power supply electrolytic capacitors. Rather the fix that failed monitor, I just a bought a new one.
The inoperative HDTV had been bought at COSTCO and had already been returned once to a COSTCO repair center for repairs. Cost to ship and insure the HDTV was 67 dollars. We received back a new HDTV set. Turn around time was over a month, with many long distance telephone calls being required. The new HDTV worked for about three months after it was received. When the returned HDTV failed, it trapped a DVD disc that had been left in the HDTV DVD player. The new HDTV failure symptoms were the same as the original HDTV failure. The red led indication would not change to green when the remotes power on button was pushed. There was no picture and no sound. The remote is required to operate the TV set.
My wife's HDTV with internal DVD player was very expensive. Worse yet, the trapped DVD disc was the movie Flash Gorden Space Soldiers 1936. A local TV shop wanted 85 dollars to look at the failed HDTV; repairs were 75 dollars labor an hour plus parts. I quickly figured out that if I could fix the problem it would save a lot of time and money.
I checked the Internet to determine if other AKAI owners had similar problems with their HDTV sets. There were lots of AKAI 27 inch and 32 inch HDTV set owners listing problems. Without exception all of the complaints concerned the HDTV power supply PC board and failed electrolytic capacitors.
General Internet Consensus:
Most of the AKAI HDTV sets worked just great and that many had been sold worldwide. There were some AKAI HDTV sets that did have power supply problems. Most of the AKAI HDTV set owners were not very pleased with either AKAI or the COSTCO response to the inoperative HDTV power supply problem.
All electrical power was removed from the HDTV set. The HDTV was placed face down on a workbench with a piece of cardboard to protect the display screen. The HDTV back panel cover was removed. There were many screws of several different sizes. The power supply PC board was separate from the rest of the set's components and was easily identified. The power supply PC board contained several different individual different voltage power supplies. Three electrolytic capacitors located on the PC board had obviously failed. The tops of these three capacitors were puffed out. Often when electrolytic capacitors fail they get over heated and the top of the capacitor is puffed out displaying an over pressurized appearance. The power supplies on the PC board were of the switching type. Switching type power supplies are also used in computer monitors to save money and weight.
Power Supply PC Board Removal:
The power supply PC board was mounted to the HDTV back panel with several screws. These screws were removed. There also several multi-pin connectors attached to the PC board. These connectors were numbered with a black felt marker to ensure correct reinstallation. The connectors were Hot-glued in place. A sharp knife was used to remove the hot glue. The connectors were removed.
The three suspect failed capacitors were easily removed. The three capacitors were each 1000 ufd and rated at 16 working volts. The other power supply PC board electrolytic capacitors were visibly checked. Three new capacitors were installed, they were rated at 1000 ufd at 25 working volts. On the PC board the three electrolytic capacitors were in just one of the power supply circuits and were identified as EC18, EC19, and EC20.
The New Electrolytic capacitors:
These were low impedance / high reliability radial lead polarized aluminum capacitors, they have a plus and minus connection pins. Correct installation of any polarized capacitor is required. The three new electrolytic capacitors were specifically designed and rated for service in switching type power supply circuits. Switching type power supply electrolytic capacitors need to be both very robust and designed for use in high frequency circuits. General-purpose aluminum electrolytic capacitors should not be used in switching type power supplies, if capacitors designed for switching power supplies can be obtained.
Final Repair Steps:
The PC board was reinstalled without the electrical connectors to the PC board being hot glued. The HDTV back panel cover was refastened. Watched episodes one through five of Space Soldiers. It was well worth the time and three electrolytic capacitors to fix the problem. The repairs saved a lot of time and money. The repair was very simple and not the least challenging. It took longer to remove and then reinstall the HDTV back cover panel than it took to replace the three failed capacitors.
These types of repairs should not be attempted without a complete understanding of the dangers involved with working on electrical equipment, especially working around power supplies and charged capacitors. Proper desoldiering and soldiering techniques need to be used.
Flat screen computer monitors and TV sets do fail. Repairs of electronic equipment can be very expensive. When your computer monitor or flat screen TV does fail, you might consider a visible inspection of the equipments power supply. A simple repair might save you a lot of time and money.
Posted on Aug 21, 2008
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