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Here is a modification that is done to every Beta I offer that does not have a static grounding system. Static grounding is a preventative measure that is intended to prolong the life of the bearings in the video drum. Every Beta has a video drum containing a spinning disc with video heads mounted on it used to write the magnetic information on to the moving video tape. In the photo above we see in the background a typical drum assembly. In front of this in the center is seen a mounting plate and the video head disk assembly (which has been removed) is mounted to this plate on the side that is facing away. Also the bearing assembly is also removed. The gray flat ring facing forward has the relay wires (green and copper color) formed in it, these send electrical signals to and from the heads. Located just to the right of this plate is the lower drum section with another mounting plate sitting in it. This one has the bearings and shaft, if you look just below it in the bottom drum you can just see a hint of the companion piece to the gray ring just discussed. This is another relay disc and it also has wires mounted in it. I mention these relay disks because they make possible the transference of electrical information between two moving components. There is no dedicated electrical connections made and the surfaces touching are those of the bearings, something to keep in mind as you read on. Located all the way to the right in the picture is the bearing assembly laying by itself. Click on the picture and you will see the rotating parts (less the video head disk and motor). As mentioned earlier the mounting assembly turns on precision ball bearings, this design has a cage to space out the rollers and an inner and outer race. This is typical of bearings found in a multitude of applications. The next photo is an enlargement that shows damaged bearing races and balls, and if you will examine them carefully you will see the problem. (The bearings are normally protected with a light-weight grease but these have been cleaned.) Notice that the curved race surfaces are covered (in the areas where they touch) with small pits and peaks. As the description at the bottom of the picture says this was caused by static electricity. When the bearings get pitted like this the video drum begins to get noisy. You would notice it first as a whirring or whining sound that changes pitch as the drum speeds up and slows down. If it gets bad enough white specks begin to show up in the picture. Where does this static electricity come from and what is it? It is caused by the displacement of electrons on surfaces that rub over one another. The most impressive example is lightening, which is caused by columns of air rubbing together and displacing large masses of electrons. When the accumulation reaches a critical mass it discharges and makes everything neutral again, a lightening bolt is the spectacular result. Another example is when you slide your shoes across a carpet and touch a door knob. That crack of electricity is the release of the electrons that you charged your body with by using your shoes as an instrument to pull them off the carpet. In the case of the video drum getting charged, it happens as the video disk slips through the air and the tape rubs against the surface of the drum. The solution to the static build-up is to give the charge someplace to go before it reaches the critical point and fires a charge through the bearings. When it discharges through the bearings the force of the moving electrons will produce an arc, as in arc welding. Small to be sure, but just the same and each time it happens a small amount of metal will be pulled away from one surface and deposited (welded) on to the other. This causes pit and peaks, the evidence of this is shown above. Now click on the picture and examine the fix. This is a ground strap that makes a bridge between the rotating center hub with the video disk and the stationary drum (the case ground). Sony once made a modification repair kit for this but never put a ground strap into production. Almost all other manufacturers have discharging grounds as part of their drum assemblies. Click on the photo and you'll see an example of the modification done to a Sony drum as well as the ones used in the manufacture by other Betas makers. VHS units were similar. Click on the photo again and you will see more examples of other types of Sony units with the modification. As you can see some, due to space limitations, have the ground custom made and mounted to the bottom of the drum. To go back to the other modifications and improvements click here. ©Misterßetamax go to homepage |