Fixing An Akai 42" LCD TV

I recently purchased an Akai 42" LCD, model LCT42Z6TM, off eBay. It was listed in "As Is" condition because it wouldn't power on. My research led me to believe that that particular model had a history of capacitor failures, and as I had recently salvaged a 15" monitor by doing a cap replacement, I thought I'd try something bigger. If I got it working, it would be a fantastic deal for an HD TV of that size, and I'd learn in the process. When I received it, much to my surprise, it worked right off the bat and it seemed like I'd been cheated out of the fun part. Fortunately, after it had a chance to warm up, wild lines started criss crossing the screen, the menus turned to gibberish, four boxes appeared in each corner, and it became clear I was going to have to fix the TV after all. In the interest of helping other potential Akai 42" owners out there, I thought I'd share what I did to repair it.


The short of it is that I replaced nine capacitors on the main board. Below I've listed the total number of each, their Farad and Voltage values, and their location on the board:

1 - 1000uf 16v - c157

2 - 47uf 16v - c143, c339

5 - 100uf 35v - c323, c301, c302, c320, c290

1 - 470uf 35v - c336

I salvaged the two 47uF 16v caps from an old DVD player and the 1000uF 16v from the rectifier/transformer brick from a dead power supply. The 100uF 35V caps I bought on eBay, 100 pieces for 11 dollars. The 470uf 35v cap I ordered locally for a whopping 50 cents. Which brings the grand total for replacement parts to $1.05. Only the 1000uf cap is a Rubicon, the rest are mid-range quality caps, but they're an improvement over the Decons that populate the whole board.




If you plan to do this yourself, you'll need the following items (most of which are pictured above): A philips head screwdriver, a soldering iron, needle nose pliers, a solder sucker or soldering braid, wire cutters, and solder. Patience and the above mentioned caps are a given. A multimeter with a cap tester is an optional.

First, place a blanket or other soft material on your work area. Lay the TV face down on it. Now remove all the screws from the back of the TV. Look around and make sure you don't miss any. Once you're sure the back of the case is loose, lift it up on the side where the power cord plugs in.




You don't want to try to just pull the back straight off at this point because the power connector is screwed on to the case and plugged into the power supply board. You have the option of either unplugging the connector from the power supply and unscrewing the green ground wire, seen above, or you can remove the two screws that hold the connector to the case. I opted for the latter.




Now, with the power connector disconnected from the case or the power supply, you can pull the back completely off and see the guts of the TV. We're interested in the main board seen in the center of this picture.




Here you see the main board for the TV up close. The offending caps are the group on the upper left corner. There are a lot of wires here that you need to carefully remove. If they've never been taken off before they'll have glue on them that you need to break off. Take note of where all of these are and where they go because it is kind of important you put them all back the same way. Remove the screws from the board itself, and use the needle nose pliers to remove the two tightening screws on the VGA connector. Once those are removed you should be able to remove the board from its little box.




Here is the board free and clear. See all those black caps labeled Decon? Those will probably fail sooner or later as well. I'm just not enough of a masochist to do the right thing and replace them all.




Here you see the upper left corner in close-up. If you're paying attention you'll see those five purple caps are actually 50v 100uf, instead of the 35v I specified above. That's because someone already capped this board at some point and used a higher voltage replacement, which is perfectly fine, but 35v is what it originally called for and what I had on hand. You may also notice nothing appears to be wrong with these caps. In an ideal world, caps pop open on the top or bottom to indicate they're shot. Sometimes, usually when they're cheaply made, they don't show any sign of a problem. I know that it's the latter in this case because replacing them did fix the TV. In all honesty, some of those caps may be just fine, but since the price was right I just swapped them all to be safe.




Here is the bottom of the board. You can see that the replacements soldered in by my predecessor have a dull finish to them. That could be a sign of a cold solder joint. The two larger caps closer to the edge of the board seem to be scorched and the metal box the board sits in is also brown directly under that spot, which suggests to me that they've probably had current arc across them. I have no photographs of me desoldering these because I only had two hands to work with, but if you're not familiar with desoldering you should probably look for instructions elsewhere anyway. The idea is to heat up the old solder and then either suck it off with a vacuum or solder sucker tool, or wick it off with a soldering braid. Do this until the wires from the capacitor are loose so you can remove them. Repeat until all the caps are out. Simple enough.




Here you see the depopulated board. You might find this helpful if you want a clear shot of the location numbers for each cap. This is also probably a good time to mention polarity. You're replacing electrolytic caps here and they need to be put in just one way. Most caps will have a stripe down one side with minus signs in it that indicate the negative terminal. On this board, the component/top side of the board has a little white block to indicate the negative side and a plus sign on the bottom/circuit side to indicate the positive. New caps will also often have a long and a short pin, with the long indicating the positive lead. Make sure you get the polarity right for every cap before you put power to this thing.




Here are the replacements. Putting them in works exactly the opposite of taking the old ones out. You generally want to work from the shortest cap to the tallest, so the big caps don't get in the way of installing the little ones. Make sure the pads are clean and as shiny as possible so the solder will hold to them. You can use electronic circuit cleaner or an old fashioned pink pencil eraser if you don't believe all the stories about it being a bad idea. I went with the latter because I like to live dangerously. I put the cap through, checking my polarity, soldered one lead and then the other, then snipped off the excess with the wire cutters.

At this point, you just reverse all the previous steps as well. Put the board back in its little box, put the screws back in, put the nuts back on the VGA connector, hook the power connector back to the case, put the case back on, put all the screws back in, and you're done.

For my 45 minutes and $1.05 I was left with this:



As you can see, the 42" is a tad larger than the 32" I already had.

Good luck to you if you're trying this. My advice is go slow, be careful, and have fun. Feel free to comment if you have a question I might be able to answer.

UPDATE: This "junk" set continues going strong. As pointed out in the comments, I had actually put one of the 100uF caps in backwards, just as the person who previously capped the TV had. Though it caused no visible issue, I have since flipped that cap around. Hopefully, no one followed my example exactly and made the same mistake.

I also determined the reason why no universal remote would work with the set. It was because the IR receiver board wasn't plugged in. How I overlooked that one I have no idea, but I hooked the board back up and now the remote works as well.

10 comments:

cdcartin2001 said...

Good writeup. I would seriously need to practice before attempting something that.

John said...

Got this out of the garbage,cost me $5.00 to fix thanks to you!!!

T. Zombie said...

That's great news! I was hoping this might prove useful to someone else one day. If you ever find a working remote control for it, let me know. I have yet to find a universal that will work with it.

John said...

http://www.remotehound.com/akai-tv-remote-replacement-tv-remote-controls-lowest-prices/akai-e7501-058001-remote.html

John said...

The T.V. is still going strong!

Colin said...

I just got a TV that is the exact same model as you worked on. I have a question and hope you read this. It powers on fine (with nothing connected)and sits with a blue screen, with the "No Signal" box that moves around the screen. It isn't until I actually hook something into it, that it gets crazy scrambled. Would replacing the capacitors fix this? I'm figuring so since the picture is perfect until a signal goes thru that board. I'm a little new at this. Thanks very much for making this page!

T. Zombie said...
This comment has been removed by the author.
T. Zombie said...

Hey Colin, it's quite possible replacing the capacitors would fix that. It's hard to recall, but I believe mine garbled the screen even when there were no devices plugged in. For instance if I let it sit on for awhile, then tried to go to the Source menu where you choose which input to use, all the text there would be distorted.

Visually inspecting all the caps I mentioned in the post (to see if they've burst open on top), would be a good place to start. Good luck!

misterlambert said...

Looks like you have C323 in backwards, just like the guy before you did. I'm glad it works just fine that way, too.

T. Zombie said...

I completely missed that! Thank you for pointing it out. I've looked back at these pictures many times and never noticed that the negative stripe on the cap didn't line up with the white mark on the component side. I'm glad it worked too, but I can't think it's healthy for it to be that way. I'll take it down this week and correct that. Thanks again.