** Build you own TV **

* Second Installment *

This time we will consider one of the more difficult parts for the average constructor to fabricate. This part is very important to achieve a smooth operating system. I'm referring to the axle or bearing for the scanning disk. This device needs to be even more precise than the scanning disk and good machining of the parts is a must. Lucky for us, there is a way, where 90% of the quality machining is already done. Here's how you do it.

Materials you will need for this installment

* "Junk" VCR

* Pulley

* Disk Hub

You need to find yourself a "junk" VCR. One that's being thrown out because it's not worth the cost of repair. Any kind of VHS machine will do. Sometimes, you may have to pay a few dollars for it, but seldom more than $5.

You only want one part out of the VCR. Its usually called the "drum and drive motor assembly". This is the part that has the rotating heads that read the signals on the tape. You need to get this assembly separated and out of the VCR. Just cut any wires that are connected to it. Do whatever you want with the rest of the VCR. vcr-head-assy

You need to remove the rotating head and driving motor parts from the assembly you've just removed. In the photo to the right, the upper arrow points to the rotating head and the lower arrow points to the bearing support after all of the electrical and mechanical motor parts have been removed and discarded. Finally, remove and discard the rotating head. You are left with the part that actually supported all of this material when it was still mounted in the VCR. It contains two precision ball bearings , a 6mm shaft and possibly a collar on one or both ends of the shaft. This will be the axle for your scanning disk.

Now here comes the hard part... You need to saw, file or machine the bearing support until it looks something like one of the other three items in the photo. This is actually a job best done on a lathe. But it's up to you as to how you do it. Here is a better photo of a finished unit. When you are bearing-supportfinished, there may be a number of extra holes present that will not affect its operation. You may even want to add one or more holes, better located to suit your mounting. If the extra holes should bother you, you can fill them with epoxy and paint the support with a flat black paint, as I do.

So far, so good. But you still need two more things. You need something to hold the scanning disk on to the shaft, (a hub) and a grooved pulley on the other end of the shaft. Both of these are lathe jobs, but maybe you can find something in a hobby shop or in your own "junk box". Here's your chance to be creative.

As I said earlier, I will also be building a monitor as we go along, so you can see how I am making the various parts for myself. To save time and trouble, I'm using an 11.75" scanning disk from a previous project. It was made of .060" engraving stock with a .75 center hole and a set of scanning holes for a horizontally scanned image. I filled the holes with black epoxy, then drilled a new spiral of 32 scanning holes and a second set of 32 larger (.062") synchronizing holes, just inside the scanning holes. This time the spiral of holes were set up for a vertically scanned image.scanning disk The disk is shown in the photo here, to the left. The holes that are readily visible are the synchronizing holes.

I have also made up a simple one piece hub to mount the disk on the bearing shaft. A set screw holds the hub fast to the shaft and three or four 4x40 screws hold the disk to the hub. The photo shows four hubs. From the left, the first three are two piece hubs that clamp onto the disk. Only the center hole is needed in the disk with this hub. The fourth hub is a one piece unit, for which three additional holes, around the center hole in the disk, are required to bolt the disk to the hub. The next photo shows the diskbearing partshub on the right, made for this project. It is approximately 1.5" in diameter and its size is not critical. Only the bore is critical. The item in the center is a pulley that fits on the other end of the bearing shaft. It is about 1" diameter and not critical either. All of these parts are made of aluminum.

Here is another view of the same parts, from a slightly different angle. ====>>>>>

 

And here's a view of the parts as assembled. The pulley is at the bottom and the disk hub is at the top.

 

 

 

Here is a view showing the hub. Note: this hub has three holes for the screws that pass through the disc, clamping it to this hub. Four screws can also be used. The disc for this hub has a 3/4" center hole. The parts that I supply come set up with four mounting holes and/or screws for the disk.

 

I recognize that this can be somewhat difficult for someone without the usual tools for this kind of work. But I have seen numerous cases where parts that accomplish the same purpose as these, have been built with nothing more elaborate than a drill press. And in some rare cases, without any power tools at all. At least try!


I am offering for sale, the hardware discussed in this installment. It consists of a disk hub, belt pulley and the ball bearing shaft assembly made from a VCR tape head/motor unit, just as described in this installment. All of the precision work is done. The hub will fit disks with .375" , .500" or .750" center holes. You will need to drill four #33 drill size holes in your disk to mount the disk to the hub with 4 X 40 X 3/8" screws and nuts.

The price of this assembly is $87 plus $.50 shipping in the USA. Order it directly from me.

Scanning discs for this monitor are also available

 


Peter Yanczer

Email me at:

pyanczer@sbcglobal.net

On to the 3rd Installment

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