Well I don't know how did it come that I am only blogging about hardware service and repairs when my major specialty and line of business is actually software...it's an interesting topic...to which I'll return sometime later.
For the time being, I became an owner of an Insignia NS-LCD32 32'' LCD TV, which wasn't powering on at all. More specifically, it was blowing the 4A fuse the moment it got connected to power and a quick test with an ampermeter showed it was ready to go way above 4A.
In my case it turned out that one of the diodes in the big recitifier in the power block has short-circuited - that was easily seen with a probe. The rectifier had US8K 80R 2566 on it and by now I don't even remember if I had managed to find its specs somehere...probably yes, but I was too impatient to make it work.
SO I went to RadioShack and bought a good 4A / 200V rectifier; it wasn't the same shape, but it was apparently powerful and it was possible to mount on the heat sink of the older rectifier; it took a little extra work with the solder to connect the new rectifier and a longer screw, but eventually it costed about $2.50 and 1 hour, including going back and forth to the nearest RadioShack.
Worked like a charm. I could see picture, switch inputs, navigate menus and everything.
Except there was no sound.
Now, before I get to the sound, I want to mention for those of you whose TVs do not blow the fuse when connected, but still can't power: there is another, apparently more popular and well known issue with this TV refusing to turn on; it's due to cheap electrolytic capacitors in the power module going bad. Replacing them fixes the problem and a temporary workaround to make the TV come on appears to be - hold on - heating it on the back with a dryier!
Here's a link for more details:
Back to lack of sound...
First off, I found out that I could get proper sound if I connect earphones; it was the main speakers that were quiet.
Here's the quick and easy solution to this and possibly nearly all other audio problems with this TV: you can replace the whole audio /HF video module. Unfortunately I do not remember what was it, but it's written on a few stamps that can be found on the board itself - the lower of the two boards on the left side of the TV when you take the cover off and look at it.
I remember I had found the board by googing for the part number that was stamped there and to my greatest surprised had found it in the CircuitCity partsearch website, along with other boards, under the ADVENT brand.
This has helped me learn that ADVENT is the actual manufactrer of the TV and that the board in reference costed around $100.
That seemed a little too much for a stupid audio! (not that I don't have them, but come on, Insignia or Advent, freakin' $100 and a whole board to the trash just because if what it turned to be a $1 audio chip?!)
Examining the board I had learned that the audio pre-processing was totally made with RENESAS technology chips: R2S15903sp (a long rectangular chip) was the pre-processor and pre-amplifier and R2S15102NP, a small square chip, is the final amplifier; there's a separate amplifier for the headphones, didn't take its number.
With the help of a cut out earphone connected directly to the output of the pre-amplifier I established that it was working fine; I could turn the volume up and down and I could hear, weak, but good enough, resopnse in the earphone.
The pre-amplifier chip was fine.
Measuring the output levels (pins 1 and 15 on R2S15102NP) returned 12V.
Sounded like a burned amplifier!
I tried to find a place on the web where I could order R2S15102NP, not even thinking how I'd be dealing with replacing the old one...because it was never meant to be replaced in the first place...but I figured I'd try if I have a good one.
It turned quite hard and I am, in fact, still waiting for quotes from the RENESAS representatives. Well, given it's Saturday and it's only been 12 hours since I sent the requests...but seriously, something tells me nobody will bother getting back to me for 1-2 pieces.
Figuring that out I decided to take the matters in my hands and started digging the RadioShack website again. I was looking for any cheap, low power amplifier that I could possibly hook up instead of the supposedly burned chip.
Did not want to replace the chip itself - it was clear I couldn't do that - just wanted to hook up ANY amplifier and see if that'll help.
Guess what: it did.
I was shooting up for the Mini Audio Amplifier, radio shack part # 277-1008, but ended up buying a Portable Folding Amplified Speaker System, part # 40-1441.
For $5 difference I got stereo amplifier.
Well you see where am I getting....
First I removed the old amplifier chip from the board; I guess I could have just cut a few lines on the board and achieved the same result, but I think removing a [supposedly] broken thing is the proper thing to do so I did it. It's a delicate job very similar to scratching off piece of old gum dried to invincibility. But with some patience, virtue and modesty I had managed to do it without detaching too many of the board lines.
Well, then the first thing I did was cut the input wire from the newly bought RadioShack amplifier, clean the wires , solder them to the amplifier inputs (actually used the legs of the two input electrolytic capacitors - soldering directly to the board would have been too delicate) .
As soon as it was connected, I plugged the board back, feeded in signal and turned on the amplifier (still on batteries).
The rest is relatively easy...time consuming, but easy. I'd just say that it turned out the RadioShack amplifier is based on TEA2025B , which, luckily takes a wide range of input power. On the TV board, on the other hand, there's a 9-volt power source (7809 or something similar) which powers the other ICs...so even though the RadioShack device asks for 6V DC it worked just great with 9V.
Ultimately, I cut of the small speakers and connected the output of the RadioShack unit to the standard TV audio outputs, took power from the 9V stabilizer on the board and stuck the whole amplifier box in the TV.
Audio is not as loud as it should be, but still totally acceptable.
Duh...sorry I did not get pictures, but I was too excited to think about that. If someone decides to take that route I wouldn't mind them taking pictures and sending them to me to point where and what to do.
$100 or some real nice hardware hacking...it's up to you :-)