My First Televisor
This was my first attempt at a complete Televisor (containing sync and sound) that I built in early 2009. It displays the NBTVA's 32 line format and is shown here to demonstrate what a first attempt can look like. The case is made of 1/4" plywood around a thicker wood base and motor support. The left hole contains a speaker for sound, and the hole on the right holds a 3" lens from a magnifying glass. The 12" disc is directly driven by a common transport motor from a VCR and as you can see from the off-screen pictures further down the page, my aperture hole drilling leaves a lot to be desired. Eventually I will replace the disc with a better one.
In its original state (shown here) the monitor used a single transistor LED driver designed by Klaas Robers of the NBTVA. This driver is a great beginner circuit, and can even be built on cardboard or a block of wood as I had done for this machine. The circuit is on the far right, just underneath the black speed control knob. It has since been replaced by one of Peter Smith's drivers, with the original used in another project, but the difference was hardly noticeable.
The board in the upper middle is the motor control circuit, which, as it's name suggests, controls the speed of the motor. This is also designed by Peter Smith and is a sister board to his LED driver. The lower middle board is a sync separator and video amplifier also designed by Klaas. It boosts the video signal and also isolates the synchronization pulse to send to the motor control board. The sound amplifier board on the left was taken and used as-is from a set of old computer speakers.
The left picture shows the machine with the door open, the right picture is the same view with the disc and back panel removed for clarity. The swinging arm in the middle left of the pictures hold the optical fork. This is an infrared LED and phototransistor pair which connects to the motor control board and provides a disc speed reference for the electronics. I placed the optical fork on a movable arm for vertical framing. If the TV picture is split vertically when locked in, a slight adjustment of the position of the arm brings it back into alignment.
This last set of pictures shows the rear of the machine without the back panel. You can see the LED resistors on the back side of the light box. Notice that the LEDs are mounted through a piece of corrugated cardboard with the leads simply twisted together!
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The whole unit is powered by a discarded Dell laptop power supply that puts out a regulated 19.5 volts, close to the 20 volts needed by the LED driver. Note: It's best to use a UL listed (or equivalent) commercial power supply and to keep it in its case. The only reason I took mine apart was to squeeze it in and keep it from pushing out too far against the back panel. Any extra protection between you and the mains (or high voltage capacitors) is well worth it.
There is also a voltage regulator mounted on a very oversized heat sink to reduce the supply's 19.5 volts down to 12 volts for the audio amplifier.
Some rather embarrassing off-screen pictures. Left is a test pattern, right is a picture of Bing Crosby, both played back from a CD player. The dark vertical lines are due to poor placement of the aperture holes. The slight waviness of the image is caused by the disc being mounted slightly off center.