Hacked LCD (given composite input)

There was a time that I would take any display that I could get my hands on and try to find a composite video signal inside it.  With that information I could modify it to take composite input from my source and I’d have a portable little lcd that I could use with my commodore 64, or raspberry pi, or… game console… this was before the C.H.I.P. or other single board computers with composite became popular.  That technique is still useful today because of the continued prevalence of composite video and the ubiquity of displays that can eat it somewhere inside.

The patient is this audiovox under-cabinet television and radio.  Let’s have a look inside.

My that’s a lot of empty space! if you look closely you can see where a dvd module would go, if this unit had one (!).  I have already hacked this one so there are some things missing.  First, you can see a lack of any RF cans full of tuning equipment, so this can’t pick up video or audio over the air anymore.  I’ll show you a picture of the back soon, but for now look at how sparse the board is (there’s more underneath but look at the unpopulated bits up here first).  There’s a section off to the right that looks to me like a modem.  I don’t know what that was for, really.  If anyone has an idea please let me know because I’m interested.  There’s also a set of unpopulated parts (including what looks like a mains section ) on the left side of the board.  That could be if there wasn’t an off-board power supply, I’m not really sure.  Looking at the parts that are present you can see a long DIP chip with some hefty capacitors, that’s the audio amp.  The connectors just above it in the picture go to the speakers.  The pole of odd stuff at the top of the board is the power supply for the VFD, there’s nothing else that would need those parts on this board.  Let’s rotate.

There’s my hack and you can see where the radio and TV tuner went.  You can also see I didn’t drill those holes, there was an option on this model to come with composite input.  I didn’t try to reverse engineer the extra feature, I just removed the other stuff and used those inputs.  Rotate again.

You can see there’s a bunch more stuff unpopulated, and the section I thought was an unused mains power supply says caution.  Enhance.

Wrong section but I can talk about it anyway.  I find this a little strange, I don’t usually see atmel ICs in the grade of consumer electronics I dissect.  I will point out I could reprogram this to add features and basically do whatever I want.  I would rather… no, this is public and if I use some colorful example someone will use it as evidence to convict me of something.  Let’s just say I won’t be doing that today.  Reposition.

Ok, here’s where I patch in the audio.  I tapped off two pins that I found near the amplifier and I removed the 4051 feeding it so that only our audio is heard.  Reposition again.

Here’s a tricky one, I actually fired up a video game, took a probe, and started injecting composite anywhere on the board I thought likely to work.  I could have probably guessed as well, but this worked really well, especially with no tuner trying to drive the screen black.

This is inside the LCD itself, there was a board to control brightness, contrast, and stuff.  You can see the ribbon that goes between the LCD and the body, I didn’t want to touch that.  So there you have it, that’s how I repurposed a thrift store screen into a portable LCD for use with my raspberry pi.  If I desired there’s plenty of room inside for the pi and a bunch more hardware, the power supply would work well too.  This currently tests composite cameras for my insecure 2.4ghz camera setup that I’m planning around (not inside) my house (post coming soon).

All photos here.

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