Camera viewfinder for the Raspberry Pi

Sadly, my Hitachi VM-600 VHS camcorder passed away. After dismantling it, I kept the useful parts including a black & white CRT viewfinder. Since I'm currently collecting parts for my Raspberry Pi, I thought it's time to put this piece back to operation.
The viewfinder has an 8-pin proprietary plug originally attached to the camera body. First thing I did was taking it apart and search for a power input on the board. I quickly noticed a secondary audio board which used 3 out of the 8 pins on the connector. An additional fourth pin was unused, thus leaving a four wire input to the video subsystem. I managed to initialize the CRT by trial and error on the four remaining pins, using a 6 volt photo battery. The high frequency humming on the board indicates it works; indeed, black and white lines were displayed. As expected, one of the remaining cables provides video signal, while the other one is the positive for lighting the red «Recording» LED. Now that wire colours are identified, I can safely assemble the eyepiece. I cut out the proprietary plug, trimmed the cables, and soldered an RCA plug for video input.

Powered by a 5 volt 180 mA DC supply, I tested the unit with a digital camera output, a Nokia N95 composite cable and a PSX game console, it works like a charm.

The viewfinder is ready to rock!

Click images to enlarge

Upper front view. This model has a microphone and an LED indicator.

Bottom view. Notice the two blue inner knobs for adjusting brightness and focus.

The audio subsystem is discarded for this project. It will probably be repurposed in the near future.

A side close up of the main viewfinder PCB. There are two more, white knobs for Vertical and H-Sync, the latter located behind the leftmost capacitor. Also notice the four-wire harness.

A picture from inside the viewfinder —what the eye can actually see. It's connected to a Nokia N95 via composite cable.

The viewfinder almost ready to be used.

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