Seeking help for an intermittent LG LST-4200A HDTV Receiver - AVS Forum
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post #1 of 4 Old 04-03-2013, 02:43 AM - Thread Starter
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I have an LG LST-4200A HDTV receiver with an intermittent open in the tuner module that I've not been able to track down. It's probably just a cold solder, but finding has been tough. A replacement tuner cost the same as the whole unit. I was just wondering if anyone else had successfully repaired a similar unit.

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post #2 of 4 Old 04-03-2013, 07:57 AM
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Most likely location for a problem is where the antenna "F" connector is soldered to the board (inside the little, metal, "match-box size" RF tuner) or where the tuner solders to the main board.
It takes a little bit of effort to get it all apart, but it's not that hard.
A good tech can fix it. You might also see if a trade school, or high school, has an electronics class, where they'd open it up and re-solder it for you, as a "show-and-tell" of what's inside the box for their students.

Ken English, Sr. Engineer, KSL-TV.
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post #3 of 4 Old 04-03-2013, 06:13 PM - Thread Starter
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Thanks kenglish,
The F connector was a good thought as it sees the most physical abuse, but my problem is with the tuner control section and not the signal path. I've opened the shielding on the tuner and probed around and can make the problem occur at will, but haven't been able to locate the surface mount component responsible. I was just taking a stab at asking in case there was a known failure point, which of course there is, the F connector smile.gif
It may be the connection to the main board, probing a tuner can be extremely difficult as with all rf it doesn't take much to alter the circuit with stray inductance/capacitance.

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post #4 of 4 Old 04-03-2013, 09:52 PM
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Wow. Wish I had of known about you a few years ago. I had the LST4200-A and it was a rock solid performer for us for a long time. But it eventually started to lose its ability to tune in and lock on to a specific channel (which happened to be the one we watched the most). Replacing the board was more than what we originally paid for it so that's what pushed me to get our first HDTV (and why I chose an LG as well). Excellent tuner.
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