I've got an old television set, an LG model 55LE5400. This TV and I have been through a lot together. I've had to replace its mainboard with ebay parts three times now, because these sets have a well-known tendency for some of their main CPU's BGA pins to work loose after several years of service. The repair method is to either fully reflow and pray, or just buy a known-working mainboard to replace it.

The TV has recently had its mainboard replaced, so it's working fine at the moment. I have also recently moved it from being a main living room TV to being a secondary TV that lives in my studio, for gaming and secondary TV watching. It's not *quite* ready to be sent to that farm up north yet. But in its current role, I am thinking I'd like to "mod" the thing to have a line-out for some powered speakers. I'm trying to identify the best place on the board to tap into the line-level audio lines before they hit the TV speaker's amplifier circuit. I'm hoping that the magic of the Empeg BBS can help me find just the right place to tap in.

Here's why I want this unusual configuration:

- I already have a stereo pair of nice self-powered speakers hooked up to the TV's headphone jack. Actually these speakers are some small near-field studio monitors I had lying around spare, so they sound pretty nice. I'm using one of those adapter cables which turns a 1/8" headphone jack into two RCA cables, and running the RCA outputs to the speakers' line level RCA inputs. This works more or less fine as-is; even though the headphone output isn't really line-level, it's at least low-powered enough not to overdrive those speakers. The TV's remote control is successful at adjusting the volume, and everything works as designed.

- I want to keep that basic layout, and keep using that pair of speakers. I don't want to buy any A/V receivers, add any additional remotes, or add any other major new components. I'm aware that my additional issues below would be solved by an A/V receiver, but I have several reasons for not wanting to add that level of complexity at the moment.

- My main issue: When something is plugged into the TV's headphone jack, it turns off all of its audio-processing features and grays them out. Through the headphone jack, it delivers pure plain stereo output without any audio processing. It turns out that there's one audio processing feature on the TV that I'd really like to use (called "clear voice II"), but I can't use that in its current configuration, due to this limitation.

- I could unplug the headphone jack, forget about the powered speakers, and just use the TV's built-in speakers. This works, it allows all of the audio-processing features to succeed, however, the built-in TV speakers are small and tinny and sound terrible.

- I have tried using the TV's fiber-optic cable output, running that to a little Toslink-to-RCA converter box, to drive the powered speakers. This produces sound to the speakers, but, it doesn't solve the problem because it adds two new additional problems: I lose volume control. The volume of the TV's fiber-optic cable output is not controlled by the TV's remote control; the remote still controls the volume of the tinny TV speakers. And if I use the TV's settings menu to turn off the TV speakers, I still can't control the volume of the Toslink output, and ALSO the audio processing features get grayed out again. In fact, I'm not convinced that the audio processing features are even working on the Toslink output at all anyway.

So I'm thinking that what I'd like to do is find the line-level part of the audio signal chain on the mainboard, right before it amplifies the sound for the TV's built-in speakers, tap into that, and turn that into a pair of RCA line-outs coming out the back of the TV. I could then unplug the connector to the TV's internal speakers, so that the remote's volume controls only the RCA line-outs and the TV speakers are silent. I believe I've identified the correct section of the mainboard, but I'm having trouble finding the datasheets for the audio amplifier chip and other components, so I don't know the pinouts. I have faith that the folks here would be able to help ID the bits I need to mess with?

I have three of these mainboards that I can experiment with at the moment: The primary one is the golden fully functional one, running in the TV right now. The second one is non-functional due to a failed reflow attempt on its main CPU; I could do practice soldering on that board perhaps. The third one is intermittently functional if I push down on the CPU's heatsink; I could use that one for testing that the mod actually works. If it works, then I could implement the final mod on the golden board.

All three boards are different revisions, and have slightly different component part numbers, but are basically the same. I'm including photos from the second and third boards so that we can ID the components and their pinouts.

Non-functional board:
IMG_4886.jpg - NTP-7100 DOJ073AG 1032 - Audio amplifier chip.
IMG_4885.jpg - 150 DK 024.T - Possibly audio amplifier transformers?
IMG_4884.jpg - Wide shot: Audio amplifier at top, transformers below, connector to TV speakers at bottom.

Intermittently-working board:
IMG_4887.jpg - NTP-7000 D01518AI 1007 - Audio amplifier chip.
IMG_4883.jpg - 150 DK PT. - Possibly audio amplifier transformers?
IMG_4882.jpg - Wide shot: Audio amplifier at top, transformers below, connector to TV speakers at bottom.

My specific questions:

- Can anyone find datasheet or pinouts for the NTP-7000/NTP-7100 audio amplifier chips? I can find the chips by googling but I'm coming up dry in locating their datasheets.

- Can anyone find a datasheet or pinouts for those "150 DK" components? Are they audio amp transformers as I suspect? I'm wondering if I merely need to tap some RCA jacks onto their top-right corner pinouts to get the line level I'm looking for?

- Any other suggestions?