Abstract:
A method of manufacturing a drum assembly associated with a digital betacam video tape machine is disclosed. The method includes providing a helical scan drum assembly having a stationary upper drum, a stationary lower drum and a plurality of rotating read/write heads disposed between the stationary upper and lower drums. The rotating read/write heads reading and writing digital information to and from a tape. The method further includes inserting air grooves in the outer peripheral surface of the upper drum. The air grooves are configured to reduce sticktion between the tape and the outer peripheral surface of the upper drum when the tape is moved around the outer peripheral surface of the upper drum. The method additional includes mounting an adjustable band to the outer peripheral surface of the lower drum. The adjustable band is configured to guide the tape around the drum assembly in accordance with helical scans when the tape is moved around the outer peripheral surface of the upper drum.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The present invention relates to video tape machines. More particularly, the present invention relates to improved techniques for manufacturing and/or refurbishing a drum assembly that is used in a video tape machine. 
         [0002]    Videotape machines that employ drum assemblies including rotating record/reproduce heads are well known. In such machines, a recording medium in the form of tape is wrapped around the drum assembly so that rotating record/reproduce heads can record and reproduce. In general, the heads rotate while the tape is moved (or held stationary) around the drum assembly. The heads may include video heads, audio heads and control track heads and in cases where video editing is needed may also include time code heads, audio confidence playback heads, audio-only erase heads, flying erase heads, etc. The drum assembly generally cooperates with loading mechanisms, reel hubs, tape guides, sensors, erase head, capstans to form a mechanical transport assembly that provides the mechanical interface between the video tape machine electronics and the information recorded on the tape. 
         [0003]    Videotape machines can be categorized using several criteria, including tape width (ranging from ¼ in up to 2 in), style (open reel and cassette), scanning method (transverse and helical scan) and recording format (e.g., U-Matic, B, C, Betacam, Digital Betacam, DV, etc.). Most commercially successful videotape machines are based on helical scanning methods. In helical scans, a slow moving tape is helically wrapped 180 degrees around the drum assembly that houses the rotating record/reproduce heads. The tape is positioned at a slight angle to the equatorial plane of the rotating record/reproduce heads. As such, the recorded tracks run diagonally across the tape from one edge to the other. Recorded tracks are parallel to each other but are at an angle to the edge of the tape. There are many recording formats that use helical scanning methods. In the C recording format (analog), the videotape machines use 1 inch oxide tape in open reels. In Digital Betacam recording format (digital), the video tape machines use ½ inch metal tape in cassettes. Digital Betacam is generally preferred over C recording formats because of its digital nature and the fact that it can be used for High Definition. 
         [0004]      FIG. 1A  illustrates a video tape machine  2  that includes a mechanical transport system  3  that is enclosed by a housing  4 . By way of example, the video tape machine may correspond to a Digital Betacam editing recorder such as the DVW, DNW, HDW models manufactured by Sony of Japan.  FIG. 1B  illustrates the mechanical transport system  3  with a loaded cassette  5 . By way of example, the mechanical transport system  3  may correspond to the mechanical transport system used in the DVW-500A model Digital Betacam editing recorder manufactured by Sony of Japan. 
         [0005]    As shown in  FIG. 1B , the mechanical transport system  3  includes a tape running system  6  having various components  11  including guides, capstan, pinch roller, tape cleaner and the like. The mechanical transport system  3  also includes stationary heads  8  and rotary heads  9  that are disposed in a drum assembly  10 . The tape running system  6  is configured to direct a tape  7  around the drum assembly  10  so that the tape  7  engages the rotary heads  9  for recording and reproducing on the tape  7 . As shown, the tape running system  6  includes at least an entrance guide  12 A for introducing the tape  7  to the drum assembly  10  and an exit guide  12 B for removing the tape  7  from the drum assembly  10 . As should be appreciated, while the tape  7  is moved around the drum assembly  10  by the tape running system  6 , the rotary heads  9  rotate at great speeds reading data from the tape  7  and writing data to the tape  7 . Although not shown, the drum assembly is in a tilted position for helical scanning. 
         [0006]    Referring to  FIGS. 2A &amp; 2B  the drum assembly  10  will be described in greater detail.  FIG. 2A  is a perspective view of the drum assembly  10 , and  FIG. 2B  is a side elevation view, in cross section, of the drum assembly  10 . As shown, the drum assembly  10  includes an upper drum  12 , an inner drum or scanner  14 , a lower drum  16 , a drum support  18 , a spindle assembly  20 , an upper base  22  and a lower base  24 . The inner drum  14 , which is disposed inside an opening  26  formed in the upper drum  12 , is attached to the spindle assembly  20 . The inner drum  14 , among other things, includes a plurality of record/reproduce heads  9  configured for video recording. The record/reproduce heads  9  are disposed in a gap formed between the upper and lower drums  12  and  16 . As should be appreciated, the record/reproduce heads  9  are rotated via the spindle assembly  20  to accomplish any recording or reproducing tasks. The inner drum  14  also includes a cavity  32  for allowing a slip ring assembly (not shown) to be positioned therein. Slip ring assemblies carry electrical signals between the rotating heads and other equipment with which the rotating head has relative motion. By way of example, representative slip ring assemblies may be found in co-pending patent application Ser. No. 09/721,436, which is titled “Slip Ring Assembly For Use In a Video Recorder” and filed on Nov. 22, 2000, and which is herein incorporated by reference. 
         [0007]    The lower base  24  is structurally coupled to the upper base  22  and the upper base  22  is structurally coupled to the lower drum  16 . The drum support  18  is configured to hold or support the upper drum  12  relative to the lower drum  16 . As should be appreciated, the tape moves over the outer peripheral surfaces  12 A and  16 A of the stationary upper and lower drums  12  and  16  while the rotary heads  9  rotate in order to record or reproduce. The lower drum  16  includes a shoulder  28  for supporting the tape and guiding the tape along the outer peripheral surfaces  12 A and  16 A of the upper and lower drums  12  and  16  adjacent the rotary recording/reproducing heads  9 . As shown in  FIG. 3A , the shoulder  28  is angled about the periphery of the lower drum  16  because of the helical scanning method used in the videotape machine (e.g., enters at high point and exits at low point). The shoulder  28  is also radially tapered so as force the tape towards the surfaces  12 A and  16 A of the upper and lower drums  12  and  16  thereby providing better contact with the heads  9 . In some cases, sticktion may be encountered when the tape is moved across the upper drum  12 . In order to reduce the sticktion, the upper drum  12  includes a pair of bumps  30  that extend past the outer peripheral surface  12 A of the upper drum  12  as shown in  FIG. 3B . The bumps  30  provide an air gap between the top edge of the backside of the tape  7  and the outer peripheral surface  12 A of the upper drum  12  (the air gap helps to reduce sticktion between the tape and the upper drum). 
         [0008]    Referring back to  FIGS. 2A and 2B , the spindle assembly  20  includes a spindle  46  and a spindle pad  48 . The spindle  46  is rotatably coupled to the upper base  22  via a set of bearings  52  and powered by a motor (not shown) housed within the lower base  24 . The motor is typically configured to rotate the spindle  46  along an axis  54  at speeds up to 10,000 revolutions per minute (rpm). One end of the spindle pad  48  is attached to the spindle  46  while the opposite end is attached to the inner drum  14 . The spindle pad  48  includes a guide post  33  and a mounting flange  50 . As shown, the guide post  33  extends into a portion of the cavity  32 , and the mounting flange  50  provides a mounting surface for securing the inner drum  14  thereto. Furthermore, the guide post  33  includes a guide hole  34  configured for supporting a slip ring assembly (not shown). 
         [0009]    Unfortunately, the design and implementation of the drum assembly  10  leads to problems which may shorten part life and the proper functioning of the video tape machine in which it is used. For example, one problem associated with the above assembly is that the upper and lower drums  12  and  16  include polished aluminum outer peripheral surfaces  12 A and  16 A. The polished aluminum outer peripheral surfaces  12 A and  16 A, which contacts the tape  7 , is not very effective at preventing sticktion problems, and it is soft material that is suceptable to wear. Referring to  FIG. 3A , the shoulder  28  that guides the tape  7  around the drum assembly  10  may wear as the tape  7  is moved across its surface. The wear can lower the position of the shoulder  28  thus shifting the position of the tape  7  relative to the heads  9 . This may make it difficult for the heads  9  to record or reproduce. The contact between the tape  7  and the outer peripheral surfaces  12 A and  16 A can also produce undesirable particles  60  (from both the shoulder and the tape). These particles may adhere to the backside or data side of the tape  7  thus causing signal dropout problems. The particles  60  may also build up on the shoulder  28  possibly shifting the position of the tape  7  relative to the heads  9  (e.g., pushing the tape away from the surface) or making it more difficult for the tape  7  to move along the shoulder  28 . The taper in the shoulder  28  may further trap particles  60  on the shoulder  28 , i.e., no place for the particles to go. All of these problems may make it difficult for the heads  9  to record or reproduce. Another problem associated with the drum assembly is that the drums are cold plated (e.g., chemical process that occurs at the molecular level) to help protect the surfaces of the drum. The cold plating process, however, distorts the shape of the drum. For example, the upper drum may be distorted into an egg shape (e.g., the diameter is not uniform). As should be appreciated, distortions such as these may make it difficult for the heads  9  to record or reproduce. Another problem associated with the drum assembly  10  is that the bumps  30  (as shown in  FIG. 3B ) tends to cause tape wear as for example shedding that produces undesirable particles  60 . It may also make it difficult for the heads  9  to record or reproduce since its only located at the top edge of the tape  7  (e.g., produces a deformed signal such as spikes). 
         [0010]    In view of the foregoing, there are desired improved methods and apparatuses for manufacturing and/or refurbishing a drum assembly used in a video tape machine such as the DVW, DNW, HDW models manufactured by Sony of Japan. 
       SUMMARY OF THE INVENTION 
       [0011]    The invention relates, in one embodiment, to a method of manufacturing a drum assembly associated with a digital betacam video tape machine. The method includes providing a helical scan drum assembly having a stationary upper drum, a stationary lower drum and a plurality of rotating read/write heads disposed between the stationary upper and lower drums. The rotating read/write heads reading and writing digital information to and from a tape. The method further includes inserting air grooves in the outer peripheral surface of the upper drum. The air grooves are configured to reduce sticktion between the tape and the outer peripheral surface of the upper drum when the tape is moved around the outer peripheral surface of the upper drum. The method additional includes mounting an adjustable band to the outer peripheral surface of the lower drum. The adjustable band is configured to guide the tape around the drum assembly in accordance with helical scans when the tape is moved around the outer peripheral surface of the upper drum. 
         [0012]    The invention relates, in another embodiment, to a drum assembly associated with a digital betacam video tape machine. The drum assembly includes an upper drum having an outer peripheral surface for receiving a tape. The outer peripheral surface of the upper drum is plated with nickel, and includes one or more air grooves disposed circumferentially therearound. The drum assembly also includes a lower drum having an outer peripheral surface for receiving the tape and an adjustable band for guiding the tape around the drum assembly. The adjustable band is mounted within a recess formed in the outer peripheral surface of the lower drum. 
         [0013]    The invention relates, in another embodiment, to a method of refurbishing a drum assembly associated with a DVW, DNW or HDW Digital Betacam editing recorder. The method includes providing an upper drum of the drum assembly. The method also includes undersizing the diameter of the upper drum. The method further includes inserting grooves in the outer peripheral surface of the upper drum. The method additionally includes oversizing the undersized diameter of the upper drum with a wear resistant material. Moreover, the method includes reducing the oversized diameter of the upper drum so that the diameter of the upper drum is within specified limitations. 
         [0014]    The invention relates, in another embodiment, to a method of refurbishing a drum assembly associated with a DVW, DNW or HDW Digital Betacam editing recorder. The method includes providing a lower drum of the drum assembly. The lower drum includes a shoulder for guiding a tape around the drum assembly. The method also includes removing the shoulder from the lower drum. The method further includes inserting a recess within the outer peripheral surface of the lower drum. The method additionally includes mounting an adjustable band within the recess. Moreover, the method includes adjusting the position of the band relative to one or more heads of the drum assembly. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]    The present invention is illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings and in which like reference numerals refer to similar elements and in which: 
           [0016]      FIG. 1A  is a broken away perspective diagram of a video tape machine. 
           [0017]      FIG. 1B  is a top view of a mechanical transport system of the video tape machine. 
           [0018]      FIG. 2A  is a perspective diagram of a drum assembly of the mechanical transport system. 
           [0019]      FIG. 2B  is a side elevation view, in cross section, of the drum assembly. 
           [0020]      FIG. 3A  is a broken away side elevation view, in cross section, showing the shoulder of the drum assembly. 
           [0021]      FIG. 3B  is a front elevation view showing the shoulder of the drum assembly. 
           [0022]      FIG. 4  is a method for manufacturing a drum assembly, in accordance with one embodiment of the present invention. 
           [0023]      FIG. 5  is an upper drum manufacturing method, in accordance with one embodiment of the present invention. 
           [0024]      FIG. 6  is a lower drum manufacturing method, in accordance with one embodiment of the present invention. 
           [0025]      FIG. 7  is a band adjustment method, in accordance with one embodiment of the present invention. 
           [0026]      FIG. 8A  is a perspective view of a drum assembly, in accordance with one embodiment of the present invention. 
           [0027]      FIG. 8B  is a perspective view of a drum assembly, in accordance with one embodiment of the present invention. 
           [0028]      FIG. 8C  is a side elevation view, in cross section, of a drum assembly, in accordance with one embodiment of the present invention. 
           [0029]      FIG. 8D  is a broken away side elevation view, in cross section, of a drum assembly  200 , in accordance with one embodiment of the present invention. 
           [0030]      FIG. 8E  is a front elevation view of a drum assembly, in accordance with one embodiment of the present invention. 
           [0031]      FIG. 8F  is a broken away diagram of an adjustable band, in accordance with one embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0032]    Embodiments of the invention are discussed below with reference to  FIGS. 4-8 . However, those skilled in the art will readily appreciate that the detailed description given herein with respect to these figures is for explanatory purposes as the invention extends beyond these limited embodiments. 
         [0033]      FIG. 4  is a method  100  for manufacturing an improved drum assembly, in accordance with one embodiment of the present invention. I one particular embodiment, the drum assembly corresponds to the drum assembly shown in  FIGS. 2 and 3 . The method  100  generally begins at block  102  where a drum assembly is received. The drum assembly may be a new or used drum assembly, although in most cases, the drum assembly is a used drum assembly. By used, it is meant that the drum assembly has been used in a video tape machine in order to read and write data to and from a tape. In most cases, used drum assemblies have detoriated to the point where the signals being generated therefrom have degraded to an unacceptable level. 
         [0034]    Following block  102 , the process flow proceeds to block  104  where the drum assembly is disassembled. This is generally accomplished using standard or conventional disassembly procedures. During the disassembly, the upper drum and lower drum are removed so that they are separate and distinct components. Once separated, the process flow proceeds to blocks  106  and  108  where the upper drum and lower drums are repaired, restored or refurbished. The repair, restoration or refurbish techniques are typically implemented to improve the performance of the drum assembly and thus the video tape machine in which it will be used (e.g., produce a better signal, reduce wear, increase life, etc.). Repairing, restoration and refurbishing may include machining, plating, grinding, polishing and the like. In one embodiment, the surface of a drum is coated with a material that reduces sticktion and reduces wear. Repairing, restoration and refurbishing may also include adding or removing components of the drum assembly to further enhance the performance of the drum assembly. For example, the air bumps may be replaced with air grooves, and the shoulder may be replaced with an adjustable band. The air grooves, which are machined into at least the upper drum, are configured to reduce sticktion problems associated with the tape riding along the outer peripheral surface of the upper drum without inducing shedding problems. The adjustable band, on the other hand, allows an operator to adjust the tape position relative to the heads so that the drum assembly produces a better signal than would have otherwise been achieved with a permanent shoulder. By way of example, the adjustable band may allow an operator to adjust the RF signal to within 5% to 10% of optimal. As should be appreciated, the fixed shoulder generally produces a signal within 20% of optimal. 
         [0035]    Once the upper and lower drums have been repaired, restored or refurbished, the process flow proceeds to block  110  where the drum assembly is reassembled. This is generally accomplished using standard and conventional procedures. Although not discussed herein, other repairing, restoring and refurbishing steps may be performed between disassembly and reassembly of the drum assembly. For example, the heads in the inner drum may be replaced, repaired, restored, refurbished, or the like. 
         [0036]      FIG. 5  is an upper drum improvement method  120 , in accordance with one embodiment of the present invention. By way of example, the method may be used in conjunction with repairing, restoration or refurbishing block  106  described in  FIG. 1 . The method  120  generally begins at block  122  where the upper drum is machined. Two machining steps are generally performed. A first machining step is performed to remove a portion of the outer peripheral surface of the upper drum (e.g., undersizing) and to form a more cylindrical upper drum (e.g., place diameter within desired TIR). The upper drum is generally radially undersized between about 0.001 in. and about 0.003 in., and more particularly about 0.002 in. In most cases, the TIR (total indicator run out) is about 0.0005. 
         [0037]    A second machining step is performed to add air grooves along the outer peripheral surface of the upper drum. The air grooves are configured to reduce sticktion associated with tape traveling around the outer peripheral surface of the upper drum. In particular, the air grooves provide an air passage that prevents vacuum related sticktion problems that would have normally occurred if such grooves were not there. The air grooves are generally machined circumferentially around the entire upper drum. It should be noted, however, that this is not a limitation and that the air grooves may only be machined in the area where the tape contacts the outer peripheral surface of the upper drum (e.g., proximate the entrance location). 
         [0038]    Any number of air grooves may be used. For example, one to about 8 air grooves may be used. In one embodiment, four air grooves are used. In another embodiment, six air grooves are used. The number of air grooves is generally dependent on the dimensions of the air grooves. As should be appreciated, the dimensions of the air grooves may be widely varied. For example, the depth may range from about 0.001 in. to about 0.020 in., and more particularly about 0.010 in. Furthermore, the height may range from about 0.001 in. to about 0.020 in. and more particularly about 0.010 in. In addition, the spacing between air grooves may range between about 0.025 in. and about 0.100 in., and more particularly about 0.050 in. The position of the air grooves may also be widely varied. For example, the first air groove maybe spaced between about 0.100 in. and about 0.300 in. from the top of the rotating heads. While not wishing to be bound by theory, it is generally believed that placing the air groove to close to the heads may adversely effect the functioning of the heads. Furthermore, the highest air groove is preferably placed at a location proximate the highest contact point between the tape and the outer peripheral surface of the upper drum. 
         [0039]    Following block  122 , the process flow proceeds to block  124  where the upper drum is plated with a material other than the material (e.g., aluminum) of the upper drum. The material is preferably selected to improve the hardness of the surface of the upper drum thus reducing wear and increasing the life of the upper drum. The material is also selected to reduce sticktion between the tape and the outer peripheral surface of the upper drum (e.g., allows the tape to more freely move therearound). The plating process and material are also selected to produce a non magnetic surface. As should be appreciated, magnetic surfaces can adversely effect recording and reproducing. In one embodiment, the upper drum is electroplated with non magnetic electroless Nickel. Nickel produces a Rockwell hardness greater than aluminum thereby preventing wear to a greater degree. By way of example, the Rockwell hardness of Nickel may be about 40 to about 60 Rc. Nickel also produces a better finish than aluminum thereby reducing sticktion. In addition and while not wishing to be bound by theory, Nickel has microscopic air pockets that are believed to help reduce sticktion. The plating process is also configured to add enough material to the upper drum so that it is oversized (e.g., outside the desired tolerances for the diameter). The amount of oversize may be widely varied, however, it is generally radially oversized between about 0.002 in. and about 0.004 in. In one particular embodiment, the upper drum is plated in accordance with C-26074E class Mill Spec. Although plating and nickel is preferred, it should be noted that other processes and materials may also be used. For example, hard anodizing may be used. 
         [0040]    Following block  124 , the process flow proceeds to block  126  where the outer peripheral surface of the upper drum is ground to the desired diameter (e.g., remove a portion of the oversize). The grinding process is performed to place the diameter of the upper drum within desired tolerances. In one embodiment, the finished diameter of the upper drum is ground to about 3.2060±0.0002 in. The grinding process may be widely varied. For example, it may be tool post lathe grinding or it may be cylindrical grinding. Furthermore, it may be a wet or dry grinding process. 
         [0041]    Following block  126 , the process flow proceeds to block  128  where the outer peripheral surface of the upper drum is polished. For example, the upper drum is spun at some predetermined rpm and the upper drum is polished back and forth longitudinally (e.g., similar to buffing). As should be appreciated, the nickel plated upper drum produces a better finish than the previous aluminum upper drum. In one embodiment, the polishing produces a high polish. While not wishing to be bound by theory, it is generally believed that the greater the polish, the greater the reduction in sticktion. 
         [0042]    The above mentioned method has been found to work well on drum assemblies that use ½ inch metal tape such as that used in video tape machines DVW, DNW, HDW models manufactured by Sony of Japan, and more particularly, the model DVW-A500. 
         [0043]      FIG. 6  is a lower drum improvement method  130 , in accordance with one embodiment of the present invention. By way of example, the method may be used in conjunction with repairing, restoring or refurbishing block  108  described in  FIG. 1 . The method  130  generally begins at block  132  where a recess in the lower drum is machined. The recess is formed in the shoulder of the lower drum. The recess follows the path of the shoulder between the entrance and exit area of the lower drum. The recess may be machined to a depth placing its surface flush with the tape contact surface of the lower drum or it may be machined to a depth greater than flush (e.g., radially inward of the tape contact surface). The recess is configured to receive an adjustable band that acts like the shoulder. Unlike the shoulder, however, the position of the adjustable band may be changed thus providing the operator with a greater ability to effect the position of the tape relative to the heads. As a result, a better signal may be produced. In one embodiment, the band includes a plurality of cutouts spaced about the length of the band for dispensing particulate formed during use of the drum assembly. The band may be formed from a variety of materials. The material chosen generally corresponds to materials that are wear resistant. By way of example materials such as steel and titanium may be used. In one embodiment, the band is formed from stainless steel. The band may be placed through a lapping process to improve the flatness of the band. The properties of the band may be further enhanced by placing the band through a nitrating or hard anodizing process. 
         [0044]    Following block  132 , the process flow proceeds block  134  where threads are tapped into the recess. The threads are configured for receiving screws. This is accomplished using standard and conventional tapping methods. Following block  134 , the process flow proceeds to block  136  where the adjustable band is mounted within the recess via screws. That is, the screws are inserted through slots in the band and secured to the threads in the recess. The screws provide a force to secure the band within the recess (e.g., sandwich). The recess is generally dimensioned to receive the adjustable band while still providing some room for adjustments (e.g., play). Following block  136 , the process flow proceeds to block  138  where the position of the band is adjusted. In most cases, the top edge of the band is adjusted to a level or height that produces the best signal when the tape is rotated around the drum assembly on the top edge of the band. 
         [0045]    The above mentioned method has been found to work well on drum assemblies that use ½ inch metal tape such as that used in video tape machines DVW, DNW, HDW models manufactured by Sony of Japan, and more particularly, the model DVW-A500. 
         [0046]      FIG. 7  is a band adjustment method  150 , in accordance with one embodiment of the present invention. By way of example, the method may generally correspond to block  138  in  FIG. 3 . Before the method begins, some pre-adjustment steps are typically taken. These pre adjustment steps generally include mounting the band to the lower drum. Although mounted, the screws are lightly tightened thereby allowing the band to move relative to the outer peripheral surface within the recess of the lower drum while being held thereto. The method  150  generally begins at block  152  where the center of the band is set to the proper position. This is generally accomplished with an indicator that measures the position of the band relative to the heads of the drum assembly. When positioned in the correct place, the center screw is tightened thus maintaining this position. In one embodiment, a specialized tool that secures to the inner drum of the drum assembly is used to measure the displacement between the heads and the top edge of the band. Because the tool is secured to the inner drum, it may rotate about the spindle axis  54  thus making it easy to measure each position. 
         [0047]    Following block  152 , the process flow proceeds to block  154  where the remainder of the band is set to the proper position. This is generally accomplished in a manner similar to the center band, i.e., using an indicator tool and tightening the screws. In most cases, the position of the band is set center to edge. That is, after the center is set, the next position outward in both directions is set and so on. 
         [0048]    Following the setting steps, the process flow proceeds to block  156  where a signal is produced (e.g., RF signal). This is generally accomplished by running a tape around the drum assembly. After producing the signal, the process flow proceeds to block  158  where a determination is made to whether the signal is within a desired limit. If the signal is within desired limits, the process flow ends (e.g., the band position is set). If the signal is not within desired limits, then the process flow proceeds to block  160  where the position of the band is adjusted. For example, the edges may be adjusted, or the entire band may be adjusted. Once adjusted, the process flow proceeds back to block  156  where a signal is produced. 
         [0049]      FIGS. 8A-8F  illustrates an improved drum assembly  200 , in accordance with one embodiment of the present invention.  FIGS. 8A and 8B  are perspective views of the drum assembly  200 ,  FIG. 8C  is a side elevation view, in cross section, of the drum assembly  200 ,  FIG. 8D  is a broken away side elevation view, in cross section, of the drum assembly  200 ,  FIG. 8E  is a front elevation view of the drum assembly  200 , and  FIG. 8F  is a broken away front elevation view of the drum assembly  200 . By way of example, the improved drum assembly may be improved using the above mentioned techniques on the drum assembly  10  shown in  FIGS. 1-3 . As shown, the drum assembly  200  includes an upper drum  202  and a lower drum  204 . The upper and lower drums  202  and  204  provide a space therebetween for rotating heads  206 . The upper drum  202  includes an outer peripheral surface  202 A and the lower drum includes an outer peripheral surface  204 A for receiving a tape  201  as it is rotated around the drum assembly  200 . The outer peripheral surfaces  202 A and  204 A may be coated with a material to reduce sticktion and wear. In one embodiment, at least the outer peripheral surface  202 A of the upper drum  202  is plated with Nickel. Nickel provides greater wear resistance and less sticktion than aluminum. 
         [0050]    In order to further reduce sticktion, the upper drum  202  includes a plurality of spaced apart air grooves  208  located about the periphery of the upper drum  202  and recessed within the outer peripheral surface  202 A. The air grooves  208  allow air to flow to the backside of the tape. The air grooves  208  are disposed above the rotating heads  206  and below the top edge of the upper drum  202 . The number of air grooves may also be widely varied. For example, the number may range between about 1 and about 10 air grooves. In one particular embodiment, 6 air grooves are used. The dimensions and configuration including position of the air grooves generally depend on the number of air grooves used. The position of the air grooves  208  may be widely varied, however, the top air groove  208 A is generally positioned proximate a point corresponding to where the top portion of the tape intersects the tape entrance of the drum assembly  200 . The dimensions of the air groves  208  may be similar or different, although in most cases they are similar. 
         [0051]    In order to guide the tape around the drum assembly  200 , the lower drum  204  includes an adjustable band  210  located partially around the lower drum  204  (e.g., from the entrance to the exit). The adjustable band  210  is secured within a recess  212  formed in the lower drum  204  via a plurality of screws  213 . The recess  212  generally has a shape that coincides with the shape of the band  210 . Referring to  FIGS. 1-3 , the recess  212  may be formed in a portion of the drum assembly  10  normally dedicated to the shoulder  28  as for example in a portion of the peripheral surface  16 A. The top edge  214  of the adjustable band  210  is configured to receive the bottom edge of the tape as its moved around the drum assembly  200 . Thus it is generally positioned proximate the location of the top edge of the shoulder of the drum assembly shown in  FIGS. 1-3 . As should be appreciated, the position of the top edge  214  relative to the heads generally determines the quality of the signal produced by the drum assembly  200 . In order to improve the signal quality, the top edge  214  may be adjusted by loosening at least a portion of the screws  213  and moving the top edge to the appropriate height and thereafter tightening the loosened screws. In most cases, only the outer edges of the band near the entrance and exit have to be readjusted, although sometimes a complete adjustment is necessary. The materials used to form the band are generally selected to prevent wear (e.g., so as to maintain the top edge position). In the illustrated embodiment, the band  210  is formed from stainless steel. This type of material has greater wear resistance over the aluminum shoulder of the drum assembly shown in  FIGS. 1-3 . For example, it may have a Rockwell hardness of greater than 50 Rc. The thickness of the band may be widely varied. When using ½ in tape having a thickness between about 1 to 3 mils (as in Digital Betacam devices) a band thickness of about 0.009 inches to about 0.25 inches, and more particularly about 0.018 inches may be used. 
         [0052]    The recess  212  is generally dimensioned a little larger than the band  210  so that the position of the band  210  may be adjusted. The depth of the recess  212  may coincide with the outer peripheral surface  204 A of the lower drum  204  or it may be recessed further within the outer peripheral surface  204 A of the lower drum  204 . In the illustrated embodiment, the recess  212  is set at a depth beyond the outer peripheral surface  204 A. This is generally done to prevent the tape from slipping into a gap formed between the surface  204 A of the lower drum  204  and the band  210 . By providing a greater depth, the band  210  is inserted past the outer peripheral surface  204 A thereby protecting the gap therebetween. The recess depth may be widely varied. In most cases, the depth is configured as ½ the thickness of the band so as to place the tape proximate the center of the band  210  (as shown in  FIG. 8D ). By way of example, when using a band thickness of about 0.018 inches, the depth of the recess may be about 0.009 inches. 
         [0053]    The top edge  214  may be continuous or it may be broken up by notches. In the illustrated embodiment, the adjustable band includes a plurality of notches  216 . The notches  216  are configured to provide space for removing unwanted particles  218  formed during use. As such, the particles do not get trapped on the top edge of the adjustable band  210 . The notch also reduces the twisting effect of the band when it is mounted to the drum. The shape of the notches  216  may be widely varied. For example, they may be curvilinear (e.g., hemisphere) or rectilinear (e.g., box like—square). In the illustrated embodiment, the notches are v shaped. This particular shape further helps to remove unwanted particles  218  from the top edge  214  of the band  210 . The number of notches  216  may also be widely varied. There is generally a balance between the number of notches  216  and the tape contact surface area  220 . In the illustrated embodiment, the notches  216  are spaced between the screws  213  As shown, there is generally one screw  213  between each of the notches  216 . In some cases, two screws may be used at the entrance and exit locations to hold the position of the band  210  to a higher degree. The length and height of the v shaped notches  216  may also be widely varied. For example, the height may be between about 0.01 inches and about 0.100 inches, and more particularly about 0.020 inches, and the length may be between about 0.01 inches and about 0.100 inches, and more particularly about 0.020 inches. 
         [0054]    As should be appreciated, bands that are draped helically around a drum tend to have edges that want to protrude radially away from the drum when mounted thereto. Therefore, in one embodiment, the outer edge of the band proximate the exit landing of the band includes a bend for sealing the exit landing of the band against the drum. Referring to  FIG. 8F , the band  210  includes a tongue  230  that is mounted to the drum  204  via a screw  213  and that extends past the exit landing  232  of the band  210 . The exit landing  232  is the place where the tape  201  exits the drum assembly  200 , i.e., leaves the band  210 . As shown, the tongue  230  includes a bend  234 . The bend  234  may be placed almost anywhere on the tongue  230 . In the illustrated embodiment, the bend  234  is placed at the interface between the exit landing  232  and the tongue  230 . The bend  234  is configured to produce a spring action that forces the exit landing  232  against the outer peripheral surface of the drum  204 . 
         [0055]    While this invention has been described in terms of several preferred embodiments, there are alterations, permutations, and equivalents, which fall within the scope of this invention. For example, although the tools and methods of the present invention have been directed at drum assemblies of video recorders associated with digital beta formats (DVW, DNW, HDW), it should be noted that this is not a limitation and that the tools and methods may also be applied to drum assemblies of video recorders using other formats, as for example, other digital formats (D2/D1) or analog beta formats (SP Beta). It should also be noted that there are many alternative ways of implementing the methods and apparatuses of the present invention. It is therefore intended that the following appended claims be interpreted as including all such alterations, permutations, and equivalents as fall within the true spirit and scope of the present invention.