My First Hack – Gateway FHX2300 Monitor Audio Out

The Equipment:

Gateway FHX2300 LCD monitor with internal speakers (Free, came with my bride), Amazon Fire TV stick ($39, Amazon.com last week), Logitech X-530 5.1 surround speakers (Free, came with a Dell 16″ monitor and partially gutted eMachine I got for a couple digits from a nice lady in another apartment last summer)

The Problem:

The Fire TV stick worked great once I learned how to boot it up right: plug in the USB power first, let it boot up, then connect to the HDMI on the screen. I realized after exploring the stick for a while that the 3.5mm audio jack in the back of the monitor was not the output I thought it was, but an input for the two internal speakers I didn’t know it had.

So I had a screen and a media acquisition and display device but no way to get sound out but a couple dollar-store speakers with all the resonant quality of a plastic pail.

After an hour of research, I found there really are no readily available or cheap solutions to say, extract the audio from the HDMI to a 3.5mm output. In desperation I settled on . . .

The Plan:

Tap into the audio circuit that handled input from the HDMI and 3.5mm TRS jack, and route the signal to a 1′-2′ cord with a female TRS jack on the end to plug my speakers into.

The Process:

I didn’t like tearing open the case one bit. I used my SOG pocket knife to pry into it, and every twist of the blade produced a new nick in the formerly flawless glossy bezel. The front now has a crack where there aint been no crack before.

IMG_1710Once it came apart, it took me a couple nights staring at the PCB and trying things out live to reverse engineer the main board and the audio circuit in it.  The 2×8-pin header in the lower left corner of the board connects what I believe is the audio-handling and amplifier circuit from a small board on the other side. Traces run out from that header up to a 4-pin jack for the speakers (driven at 2.5V) in the upper left corner of the board. Having learned that the typical output from a consumer-grade TRS jack runs at about .5V maximum, I was hoping that I would be able to steal an un-amplified signal right off that header at a safe amplitude. That didn’t work out. There was no such output on the header. Instead I opted to simply clip off the internal speakers and splice my output cable into their old arteries. I thought I would try to protect my speakers’ input by adding a simple voltage-divider attenuator circuit into the mix. This proved unnecessary. Once I made the splice on the terminal strip, I tested the output with a pair of headphones I had lying in a drawer. Nothing exploded! This was clearly a blessing on my progress so far that demanded a proper finish.

Repaired button board

In the middle of trying and testing on the desk, I made a cardinal mistake. I plugged the main board into power before plugging in the button board that contained the Power On switch. I accidentally dropped the board directly onto the main board, just above where the leads from the AC input jack were soldered. When I moved to pick it back up, it shifted just enough to short the 120V and pop went the weasel. Sure enough, the back of the button board was damaged and would not power up the monitor. Where the red wire on the left is soldered to the board used to be two pads for what I believe was a resistor for the LED to the right. I simply soldered across it (it exploded) with the wire and terminated the other end where the blown trace used to end. Notice the pale line where I removed the broken copper.

IMG_1722Once the button board was back in service, I finished up by supergluing the audio out cable to the side of the terminal strip and screwing the terminal strip to the top of the steel case. I laid tape across the wires to secure them, and reassembled the screen and all that other stuff. The new 2′ whip of audio out cable popped neatly out through the hole for the built-in audio input jack.
IMG_1729
OK to ship! A feature-enriched computer monitor made functionally indistinguishable from any TV screen.
The Lessons:
  1. Never buy what you can build (or hack).
  2. Always research your project heavily. Go crazy and don’t fear breaking it.
  3. Always observe lesson #2 only in that order.
  4. Always take the fox and the lettuce across the river before you bring the rabbit. See The Process, Paragraph 3.
  5. Never set your heart on material things. They go hard at disappointing when they break.

Ciao! I’ll write again when I have something else to break.

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4 thoughts on “My First Hack – Gateway FHX2300 Monitor Audio Out

  1. Nice hack! Nice recovery, too, when you blew the trace.

    This brings back a memory of something my dad did when I was a boy. To help an elderly couple who argued over the volume on the TV when one was watching and the other wasn’t, my dad installed a 1/4″ phone jack so they could plug in a pair of headphones.

    Enjoy the audio on your new home theater!

    Like

  2. Not bad at all! You crafty thing. It’s ever so much fun to diy–actually learning something rather than dropping money and ending up with superfluous tech.
    I’ve got an old lcd that’s begging to be played with but it’s impossible to find proper pinouts on her… you and your Pi would probably have better luck making use of it though.

    Love to hear what else you’re working on, post ’em if you’ve got ’em.

    Like

  3. Caleb says:

    Reminds me of a joke Jennifer recently shared with me. “Instead of going to Starbucks, I make my own coffee, yell my name out incorrectly, and light a $5 bill on fire.” For those of us with the time and inclination, making our own coffee, sans currency-incineration, is the way to go.

    Like

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