Build Your Own TV

Installment Eight

Getting it all together

At this point, you should have most of the parts for the monitor made up or at hand for final assembly. Start by mounting the major components on the top rear cover. These four photos below, show the locations of the VCR bearing mount, the motor and the LED array.

The bearing mount and scanning disk should be centered from (from left to right) with the disk centered in the slot between the front and rear covers. Install the scanning disk on the bearing mount and when you have the location for the mount set, install screws, nuts and washers as necessary to firmly attach the the bearing mount to the top cover. The disk face should also be perpendicular to the bottom.

monitor top pix 1






monitor top pix 3monitor top pix 4

monitor top pix 2

The scanning disk has been removed here so the photos might show more detail.

The motor can be mounted to either side of the bearing assembly. The belt is a rubber "O"ring with a 3/32" cross section (1/16" will also do) and there are various rubber VCR belts , some square in cross section that will also work. The "O" ring is approximately 2.25" diameter when off the pulleys and relaxed. The belt size is not critical; anything between two and three inches will do. The pulleys should be in line and the motor shaft and disk bearing shaft parallel. Belt tension can be best described as light. If necessary, tension can be increased later.



The photos of this second monitor ( this one has a clear plastic top cover ) shows the motor located on the other side of the bearing mount, somewhat between the LED array and the bearing mount. There is no particular advantage to either mounting of the motor, except that the motor leads here are slightly shorter. Notice that on the two pictures on the left that the 4 pin motor/LED wiring connector is visible. The male connector is located on a bracket attached to the side panel.

To locate the LED array, install the scanning disk and apply 5 to 6 volts DC to the LED array and position the array so that its center of illumination (vertically) is at the same height as the center of the disk bearing shaft. Rotate the disk by hand or apply the same voltage used to excite the array, to the motor leads. With the motor running, look through the scanning holes at the light from the array and shift the array sideways (you already know the correct height) until it is able to illuminate all of the scanning holes. Where this occurs is the required horizontal/vertical location for the array. In addition, the array should be very near the rear surface of the disk. Your array should have a thin section of felt on its front surface (see installment 4 ), to act as a cushion where it may come in contact with the disk. When you have established the proper location for the array, mount it firmly to the top cover. If the LEDs in the array are exposed, you might consider making up some sort of enclosure to minimize stray light from the LEDs.

The next thing to do is to mount the various components in the cabinet. While the scanning disk is still in place, locate the sync fork on the cabinet bottom. It may be necessary to move the fork a small amount (left or right, less than 1 inch) during final testing, so provide some means to allow this adjustment to be made. These next two photos show the fork in a mounting that

is adjustable, but this mounting is just a "bell and a whistle" and not necessary for satisfactory operation of this monitor. When you mount the fork, keep in mind the it must sense the row of sync holes in the disk, so the sensor and its light source must be at the correct height. The photo on the left also shows the connector for the motor and array, where it is mounted on the side panel.

Installments 5 and 7 include a number of photos showing the location of the various components that make up the monitor. Layout is not critical, but generally the components are located so as to minimize the length of associated wire runs. Be certain that no wiring or components interfere with the operation of the scanning disk.

Electrical hook up of the sync separator and LED drive requires an input connection from an RCA jack on the rear panel to the front panel Gain or Contrast control and to the circuit board using shielded wire. The Brilliance control is also a front panel control and ordinary wire will do. Wiring to the array, including the motor/array connector is best that it be shielded. The same can be said for the sync pulse wire to the second circuit board. The Speed control is on the front panel and it and the motor itself require only standard wiring. The wire from pin 2 of the QSE 156QT should be a shielded wire. On the audio amplifier, only the wire from the audio jack on the rear panel to the front panel Volume control and from it to the circuit board needs to be shielded.

Next time we will do some testing.

End, Installment Eight

Peter Yanczer

On to installment #9, Testing



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