Build your own TV
Installment Seven

Materials you will need for this installment:
Power supply components
Misc controls, one with a switch
Front and rear panel material
Misc wire


In the previous installment you were given three circuit diagrams, the Video/Sync circuit, the Phase Comparator/Motor Driver and the Audio Amplifier. The first two are powered by a 15-volt DC source and the Audio Amplifier requires a 12-volt source. The schematic for the two DC sources is shown here on the right. pwr supply schematicThe supplies are identical except for the regulator I.C. which is a type 7815 regulator in the 15-volt source and a type 7812 in the 12-volt source. Both regulator I.C.s are fitted with small heat sinks.

Since I used printed circuit boards to contain the various components, I included the power supply components ( minus the transformers) on each of the three boards. You might prefer to use separate small pieces of vector board for these parts.

There are a number of choices available to you when building the power supplies. One "large" power transformer can be used to supply the entire load or two or three smaller ones can do just as well. "Large" is a relative term here, in that relatively small transformers are required in any case.

In my own situation, I used two transformers, the larger of the two rated at 17 volts, .35 amperes. It supplies the 15-volt D.C. circuits. The other transformer was rated at 14 volts at .2 amperes and it supplies the Audio Amplifier only. One 17 volt transformer with a .5 ampere rating could also have be used to supply all three circuits, in which case a slightly larger heat sink on the 7812 regulator might be necessary.

Transformers with up to 20-volt outputs can be used, but more heat will be dissapated by the regulators, so larger heat sinks will be necessary.

If you haven't already done so on your own, you might now install the four controls on a section of aluminum angle or wooden equivalent and mount the assembly on the base of the cabinet. Here is a photo showing the receiver construction.

receiver assembly view

Looking at the front of the cabinet, starting from the left, the controls are the Volume (and switch), the Contrast, the Brightness and the Motor Speed. The shafts on the controls should be long enough to pass through and an additional 3/8" to 1/2" beyond the front panel.

If you haven't made up a front panel yet, do it now. I used 1/8" thick black Micarta, which looks like Bakelite. Wood, metal or plastic are all suitable. The rear panel can be the same material as the front panel. On it, you can mount the main power toggle switch and a hole for the line cord. Two RCA jacks for the input video and sound signals are also mounted on the rear panel. In my case, I used a section of 3/4" X 2" aluminum angle for the rear panel.

You might now mount the transformer(s), circuit assemblies and speaker in appropriate locations. Keep in mind that the scanning disk will be passing through the cabinet when the set is operating. If you place the two top covers on the cabinet, there will be an approximate 1/2" gap between them. This is where the scanning disk will be located. You do not want any of the parts in the cabinet to interfere with the operation of the scanning disk. Stay at least a 1/2" away from where the disk will be at all points.

Somewhere on the inside of the cabinet, you will need a termination for the motor and LED array wiring, mounted on the TOP, rear surface. I used four pins of a small five-pin male/female connector. The female part is on a short length of angle bracket, mounted on the side panel. The male part of the connector is on about six inches of cable attached to the rear TOP underside surface.

When you have all of the parts except the sync fork in place in the cabinet, you can begin wiring the Audio Amplifier to the 12-volt supply and the volume control. Then continue by getting the 15 volt supply working. The Audio Amplifier can be easily tested with inputs from signal generators, radios or phono pickups. If you have an oscilloscope, it will be the best instrument for testing the circuits in the monitor. When you are satisfied that the power supplies and audio amplifier working, don't do any further wiring until the motor, disc bearing assembly and LED array are set up on the top rear cover. That will be covered in the next installment.

End, Installment Seven

Peter Yanczer

This message is to those of you that are building your monitor, per these installments.

The next installment, number eight will most likely complete the construction of the monitor. Following that, there will be one additional installment on the subject of troubleshooting. I also wish to develop an FAQ (frequently asked questions) based on questions from the readership,(that's you!) that I will try to answer and place these on this site.

This might also be a time to consider where you are going to get a 32 line television signal to operate this monitor. For those of you that are patient, I plan to begin a series of installments on a 32 line camera, most likely of the direct view variety. However if you are in a hurry (as I would be), I strongly recommend you contact the NBTVA ( there is a link on this site) and purchase one of their CDs (second version). Do yourself a favor and join their club at the same time.

So if you have questions of me, write or Email me, as of now.

Thank you for your interest.

Peter Yanczer

On to installment eight

 

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