Identification and disassembly
I recently found a nice 1987 Sony Watchman FD-10A for a reasonable price at a local thrift store. Since I have a soft spot for CRTs and had never seen one of these funny little squished rectangular tubes in person, I picked it up.
Thankfully, it worked just fine and didn’t need any basic repairs or CRT adjustments. As a very simple somewhat cost reduced Watchman, it only supports analog over-the-air VHF and UHF TV signals and mono audio. It does have a mono ear phone jack, but no other video or audio external adjustments or connections.
So, these days, it is pretty useless unless we can mod it to take composite input. Other people have successfully done so and posted some information about how online. Unfortunately, there appear to possibly be two or three revisions of the FD-10A and my revision didn’t appear to be documented. So let’s get to work!
Finding Space
This FD-10A has the newer surface mount A/V chip, which needs to be removed in order to inject an external signal. It’s fiddly work, but not terribly difficult. The other big decision to make when doing this mod is where to put the RCA plugs. Other people have mounted individual jacks to various places inside the battery compartment and come up with alternative ways to power the TV, such as a smaller lithium battery or adding an external power cable.
I still wanted to use mine with batteries, and I didn’t want to add unnecessary holes, so I decided to replace the no longer needed antenna with female RCA pigtails. They fit perfectly through the antenna hole with a simple knot for strain relief and tuck neatly above the top of the main circuit board when reassembled.
Locating the Right Pins
The wiring of the plug is very simple…if you know the right pins to attach them to! The ground wires of both plugs were soldered to the RF tuner case lugs. None of the info I was able to find online had the correct audio and video pins identified for this particular FD-10A. But after a bit of poking around, I located the video input on pin 19 and the audio input on pin 24. Success!
Final Thoughts
I covered over the exposed wire connections and the rest of the now bare IC pads with kapton tape for safety and buttoned up the TV. Now I have an extremely portable TV for testing any device that outputs composite video. I’m thrilled to be able to add it to my collection and would be happy to do a similar mod for anyone else with a similar Watchman.
