HamCall (October 1991)

home *** CD-ROM | disk | FTP | other *** search

/ HamCall (October 1991) / HamCall (Whitehall Publishing)(1991).bin / bcast / miscbcst / cartmech.txt < prev next >

Wrap

Text File | 1990-10-14 | 38KB | 694 lines

********************************************************************* * NOTE: The following ASCII text file (without graphics) * * is contained in a printed technical paper available * * from Broadcast Electronics Inc. Unfortunately, it * * was not possible to reproduce the graphics portions * * of this paper within this text file. If you find the * * information in this file of interest, you may request * * a complimentary, printed, copy including figures and * * graphics from: BROADCAST ELECTRONICS INC. * * P.O. BOX 3606 * * 4100 N. 24TH STREET * * QUINCY, IL. 62305-3606 * * ATTN: SALES DEPARTMENT * * PH 217-224-9600 * * FAX 217-224-9607 * * * * The contents of this technical paper are * * Copyrighted (c) 1987, by Broadcast Electronics Inc. * * All rights reserved. * ********************************************************************* TAPE CARTRIDGE TRANSPORT SYSTEMS: DESIGN, OPERATION AND MAINTENANCE Jeffrey H. Steinkamp, P.E. Broadcast Electronics, Inc. Quincy, Illinois Presented: April 1987 I. INTRODUCTION The tape cartridge transport system is the key mechanical element of today's modern cart machine. The purpose of the transport system for NAB (National Association of Broadcasters) type tape cartridges is quite simple: support the cartridge and pull the magnetic tape across the heads at the proper speed. Accomplishing this task requires knowledge and technical expertise in many areas of design. Proper design engineering and testing of the many components that comprise this system are paramount in producing a functional, reliable product. This paper will discuss the design philosophy and specifics of each of these components. Items discussed include the deck plate, solenoid, drive cable, drive cam, cross shaft, pressure roller shaft, pressure roller, motor capstan, cartridge guides and head box. The functional operating relationships between these components that make up the transport system will be reviewed. A free body force diagram will detail the relationships between solenoid force, pressure roller force and tape pull force. And finally, a section covering the proper maintenance of this system will be included. NOTE: All of the design, operation and maintenance data dis- cussed in this paper are in reference to Broadcast Electronic's new "C" series tape cartridge transport system. II. COMPONENT DESIGN Deck Plate - The deck plate (see Fig. 1) is the foundation of the tape transport system. It is the platform that contains all of the other assembled components. The deck must be strong, stable, yet simple in design. It must functionally position the right hand cartridge guide, the head box, the pressure roller and motor capstan in accordance with NAB specifications. Proper placement of these items will assure workable interaction with NAB designed tape cartridges. To maintain the critical locations of components, the deck must be correctly dimensioned and tightly toleranced. Tolerance levels of +/- .002" are quite common. The best material for deck design is .500" thick aluminum tool plate (6061-T651 Type 200) which has excellent strength, stability and surface flatness characteristics. To maintain proper perpendicu- larity between the deck surface and the motor capstan, a high degree of flatness and parallelism must exist between both the top and bottom surface of the deck. Readings of only .005" TIR (Total Indicator Reading) for both flatness and parallelism must be maintained. The top surface roughness of the deck should not exceed 32 microinches (1 microinch = .000001 inch) with a lay or graining direction parallel to the motion of cartridge insertion. This extra smooth surface finish eliminates unnecessary wear on the plastic-bodied tape cartridges. To help protect this smooth finish, the deck should be clear anodized to the MIL-A-8625 specification. Anodizing is an electrochemical plating process that hardens the surface of aluminum, gives increased corrosion resistance and preserves aluminum's original aesthetic appearance. As with all components, the deck must be closely inspected by the Quality Control department to guarantee 100% adherence to all design parameters. Solenoid The purpose of the solenoid (see Fig. 1) in a tape transport system is to supply motion to the drive cam and cross shaft to rotate the pressure roller into position against the tape and motor capstan. There are two major components of a solenoid, the body and plunger. The body contains the electro- magnetic coil and should be of sturdy design with a non-corrosive zinc or cadmium plated finish. The body should have adequate means to aid in mechanical mounting of the solenoid. The plunger should be coated with a Teflon based low friction finish (Impreglon #218 or equal) to assist in repeated smooth operation. A tapped hole located in the face of the plunger is required to mechanically attach the cross shaft drive cable. Equally spaced holes around the circumference of the exposed end of the plunger will aid in rotating the plunger during final adjustment. The solenoid converts DC voltage into linear motion of the plunger by the creation of a magnetic field within the body of the solenoid. Solenoid per- formance is best described graphically (see Fig. 2) in terms of stroke/force/voltage curves. For any given solenoid, the force at the plunger varies with stroke position and applied voltage. The stroke measurement is defined as the plunger distance out from the fully seated or bottomed position. Internal or coil temperature can have a weakening effect on solenoid performance. As the coil temperature increases, so does the coil electrical resistance. This increased resistance will result in lower current flow for a constant voltage level. This decreased current will decrease the force performance of the solenoid. To overcome the effect, the use of a constant current supply to the solenoid and adequate thermal dissipation and ventilation are required. Solenoids in tape drive systems must not only be strong pulling but also quiet in operation. To slow down the fast moving plunger, an adjustable air dampening device is mounted to the rear of the solenoid. Dampening adjustment of the solenoid allows the drive system to be adjusted within the NAB specifications for transport start and stop times and yet be quiet in operation. Although stroke/force/voltage performance will vary from solenoid to solenoid, a tight quality control program with sample testing will prevent many problems. Drive Cable - The element that transfers the linear force from the solenoid plunger to the drive cam is the cross shaft drive cable (see Fig. 1). This linkage must be strong, flexible, lightweight, adjustable and non-magnetic. The use of a .046" dia. 7 x 19 stainless steel cable with an attached threaded brass stud meets all of these requirements. The maximum impact tension force for this cable in actual use would be 27 lbs., well below the cables breaking strength of 270 lbs. (Factor of Safety 10:1). Cable of 7 x 19 construction (7 strands of 19 wires each) is used where flexibility and good resistance to wear is required. Successful life testing of this cable to over 2 million cycles indicates that fatigue failure is not a problem. The lightweight design of this cable at .006 #/ft. versus miniature chain link at .094 #/ft. is beneficial in faster start times due to lower mass inertia. Cable drive systems are also much quieter than the rattle of chain driven designs. The brass threaded portion located at the end of the cable allows mechanical attachment to the solenoid plunger and prevents the conduction of any magnetic flux to the rest of the system. At mid-span of the cable is a swaged brass ball or bead that will fit into a socket on the drive cam. This ball-socket arrangement allows the cable to grip the cam. At the other end of the cable is a lug that accommodates the return spring. Drive Cam The function of the cross shaft drive cam (see Fig. 1) is to convert the .80 inch linear movement of the solenoid plunger/ drive cable to rotary motion of 105 degrees. The cam shape, which is basically a wheel with an offset center hole, allows the trade off of slightly more linear motion of the solenoid for increased leverage on the cross shaft. This mechanical advantage allows for more pressure roller indentation and improved tape pull. The drive cam is manufactured from Delrin 500 thermoplastic plastic. Delrin acetal resins are homopolymers that possess the needed characteristics of strength, rigidity, resilience and resistance to creep, high fatigue endurance, resistance to repeated impact, low static and dynamic friction, with resistance to most solvents and chemicals. Lightweight design and good cosmetics are also an added plus for Delrin material. As with the drive cable, the drive cam has been cycled over 2 million times with nearly undetectable amounts of wear. Cross Shaft The cross shaft (see Fig. 1) transmits the rotary motion and torque from the drive cam to the pressure roller shaft. This rotation of 105 degrees brings the pressure roller up into position to engage the tape and motor capstan. Material selection is critical in the design of the cross shaft. Non-corrosive, non-magnetic Type 303 stainless steel rod that has been centerless ground and polished is the best choice. Grinding the diameter to a tolerance of +/- .0005" with a surface finish of 8 microinches is essential. The tight toleranced diameter will assure wobble-free fit into the equally precise hole in the deck plate. Addition of silicon grease lubrication in tandem with the extremely smooth polished finish will result in a low friction, non-binding operation. Pressure Roller Shaft The purpose of the pressure roller shaft (see Fig. 1) is to support the pressure roller on the cross shaft. This shaft must mechanically locate the pressure roller off the surface of the deck plate in accordance with NAB standards. These dimensions must be held precisely so the pressure roller will rotate up through the cartridge key hole and engage the tape properly. Due to the high velocity rotation and resultant impact of the pressure roller against the motor capstan, the pressure roller shaft must be able to withstand high stress loading. Stainless steel is again the choice because of its high strength, good ductility and non-corrosive properties. Adequate care should be given in fabrication of this shaft to use generous radius in all machining to eliminate unwanted stress concentrations. The bearing area of the pressure roller shaft should be ground to a diametrical tolerance of +/- .00025" with a polished surface finish of 10 microinches. The purpose of this grind and polish is two fold: one, to produce a low friction interface with the pressure roller bearing; and two, provide a tight bearing fit to prevent unwanted movement and resultant tape speed fluctuations. Other features in this design include wrench flats or hex body to facilitate installation or removal of the shaft. A snap ring on the top end of the shaft allows for quick and easy removal of the pressure roller if required. Pressure Roller The pressure roller (see Fig. 1) rotates up through the keyhole in the cartridge. It pinches the tape between itself and the rotating motor capstan which causes linear movement of the tape. During normal operation, the motor capstan drives the pressure roller and the pressure roller in turn pulls the tape. Tape slippage occurs when the force required to pull the tape from the cartridge exceeds the force created by the pressure roller and motor capstan. At this point, the pressure roller and tape cease moving even though the capstan may continue to rotate. Tape pull is directly related to pressure roller indentation against the capstan for a given pressure roller design. More discussion of this relationship will be presented later in this paper. The pressure roller consists of three parts, the roller, the bushing and the bearing. The roller material is polyurethane which is a copolymer thermoplastic elastomer. Polyurethane is the ideal selection for the roller because of the following characteristics: outstanding wear, flex and tear resistance, high resilience, good elasticity, very slow aging and resistance to most solvents and chemicals. After casting or molding, the surface must be ground to a 32 microinch finish for good adhesion to the tape. Durometer readings, which measure the hardness of elastic products, must be tightly controlled. The outside diameter is held to +/- .003" to prevent unwanted elliptically shaped parts. The natural clear transparent color of urethane is selected to aid Quality Control inspection of any internal air pockets, voids or defects. The urethane roller is permanently bonded to the aluminum bushing during the casting/molding process. The bushing is the interface between the roller and the bearing. The inside diameter of the bushing must be held with tight tolerances of +/- .0005" to provide a snug fit between the bushing and the bearing. The bearing used in the pressure roller is a non-metallic, self- lubricating type fabricated from Turcite material. Turcite is a PTFE (Polytetrafluoroethylene) thermoplastic based product. Turcite bearings have excellent wear resistant properties, low friction, low creep, good pressure/velocity bearing performance and are impervious to most chemicals. This material was selected because of its self-lubricating and quiet running operation. Pressure roller fabrication is very critical in the performance of the tape cartridge machine. An improperly balanced pressure roller will play havoc with tape speed specifications. To solve this problem it is mandatory that the completely assembled pressure roller system (roller, bushing, bearing) be match machined to maintain precision concentricity (.002" TIR) between the roller outside diameter and the bearing inside diameter. Motor Capstan This paper will limit itself to just the mechanical aspects of the cart machine motor namely the motor capstan (see Fig. 1). Precision shaft diameter is critical to maintain constant tape speed. A diameter tolerance of +/- .0001" is required on the stainless steel non-magnetic shaft. This shaft must be sandblasted and then hard chromed to just the right finish for proper tape pull performance. Not only is the static diameter of the shaft critical, but the shaft when rotated cannot wobble by more than .00015 inches. Just as in the case of the pressure roller, this rotating trueness is important to good cart machine performance. The position of the motor capstan relative to the deck plate must be as near perpendicular as possible. Specifications on the motor drawing should call out for shaft to mounting block angular dimensions of 90 degrees +/- .25 degrees. As discussed before, the flatness and parallelism of the deck plate is key to proper component assembly of the motor and deck. Incoming quality control of the motor to sort out any damaged or out of specification motor capstans is essential to producing a quality product to the customer. Cartridge Guidance System The tape cartridge must be exactly positioned on the deck plate to result in top performance. This positioning is the function of the cartridge guidance system (see Fig. 1). As the cartridge is placed in the mouth of the cart machine, the cartridge must be positioned firmly downward on the deck and also sideways against the right hand cartridge guide. The insertion of the cartridge is of course stopped by the head box main frame. These three bench marks, namely the deck plate, right-hand cartridge guide and head box main frame, are specifically located by NAB code and cannot be violated. Pressure pads supply the downward force and can be adjusted for optimum drag for NAB type cartridges. The spring on the left hand cartridge guide forces the tape carrier to the far right during insertion. The aluminum material used in the manufacturing of the left and right hand cartridge guides is adequately strong and is black anodized (MIL-A-8625) for increased wear resistance and cosmetic appearance. The pressure pads are molded from black Delrin 500, a plastic material of low friction coefficient and high abrasion resistance (see drive cam material). Head Box See included paper titled: "PHASE LOK V HEAD BOX ASSEMBLY: DESIGN, OPERATION, ALIGNMENT AND MAINTENANCE" By Richard L. Anderson. III. SYSTEM OPERATION The purpose of the tape cartridge transport system is to correctly guide an inserted NAB cartridge in to position, rotate the pressure roller up into place against the motor capstan and pull the magnetic tape across the heads located in the head box. After pressure roller rotation, the system must reach a point of equilibrium. This balanced condition can best be described by the use of a free body diagram (FBD) (see Fig. 3). As in every free body diagram, the summation of all forces and moments (torques) must equal zero. In the diagram of Fig. 3, only the total moments about the cross shaft (Mcs) will be of concern. Thus: Mcs = (Fs)(L1) - (Frs)(L2) - (Fpr)(L3) = 0 Where: Fs = Force Of Solenoid (lbs.) Frs = Force Of Return Spring (lbs.) Fpr = Force On Pressure Roller (lbs.) L1 = Distance From Fs To Cross Shaft Center Line (in.) L2 = Distance From Frs To Cross Shaft Center Line (in.) L3 = Distance From Fpr To Cross Shaft Center Line (in.) Knowing Frs, L1, L2 and L3 for the "C" series design, one can solve for Fs and Fpr. Those results are presented in Fig. 4. It is quite obvious that the amount of pressure roller force (Fpr) is directly related to solenoid force (Fs). As solenoid force increases, so does pressure roller force. As pressure roller force increases, the urethane roller is pressed tighter against the motor capstan. This force causes increased indention of the pressure roller. This force versus indentation is well defined for a given urethane pressure roller with fixed diameter, height and durometer (hardness). Likewise, as the indentation increases on the pressure roller, the ability to pull tape also increases. This tape pull force (Ftp), pressure roller force (Fpr) and roller indentation relationship can be reviewed in Fig. 5 with the actual numerical results in Fig. 4. So far, only the mechanical aspects of the pressure roller indenta- tion and tape pull have been discussed. In reality, an optimum indentation must be determined in regards to wow/flutter readings. With too little indentation (less than .010") tape slippage occurs, with too much indentation (greater than .020") an unwanted rotating lumping action occurs. Thus, the ideal compromise between good tape pull and low wow/flutter readings is near the .015" indentation point. Therefore, the tape transport system must be designed to stabilize at this point of equilibrium. Adequate tape pull is a controversial topic for today's broad- caster. With the recent introduction of HOLN (high output, low noise) lubricated tape in NAB cartridges, the ability to success- fully pull these tapes is in question. Due to these so called "hot" tape's smoother surface, lower coefficient of friction and tendency to pack tighter, it requires additional force to pull these tapes out of the cartridge. The "C" series tape transport system was especially designed to be strong pulling without affecting tape speed. At the indentation value of .015", a tape pull of 1.0 lbs (16 oz) is accomplished. From extensive testing of NAB cartridges with "hot" tapes, this 1.0 lb pull capability of Broadcast Electronic's system is comfortably sufficient. IV. SYSTEM MAINTENANCE The three goals of maintaining any piece of equipment are: keep it clean, keep it oiled and keep it adjusted. These goals are quite appropriate for the tape transport system. Scheduled housecleaning of the system should be standard procedure for every cart machine owner. The overall system should be kept free of dust, dirt and foreign contamination. The motor capstan and pressure roller should be cleaned daily with isopropyl alcohol to remove all traces of tape oxide or tape lubricant. Use of a clean cloth or Q-tip is recommended. Periodic cleaning of the inside diameter of the pressure roller bearing with isopropyl alcohol, although not required, is beneficial to increased bearing life. Since all of the components needing lubrication are either factory greased or self-lubricating, the "C" series system is essentially maintenance free. For instance, the motor contains permanently lubricated ball bearings and the Turcite pressure roller bearing is self-lubricating. The cross shaft is factory lubricated with silicone-based grease and the drive cable is pre-oiled. The teflon based coating on the solenoid plunger likewise requires no additional maintenance. Proper adjustment of the tape transport system is essential to good, reliable performance. At times, periodic adjustment may become necessary for the cartridge guidance system, pressure roller/motor capstan and solenoid setting. Refer to the techni- cal manual for instructions and gaging information. V. CONCLUSIONS Proper design, operation and maintenance of a tape cartridge transport system is critical to a successful broadcasting organi- zation. The cart machine manufacturer must apply sound fundamental engineering principles to the design. Broad knowledge of mechanisms, statics, dynamic motion, material selection, and manufacturing technique are just a few of the specializations needed. Mixed in with all this theory must be a foundation of common sense and a commitment to a quality product. The cart machine owner must understand the operation and maintenance requirements of his own unique system in order to produce a cost effective yet quality signal to the listener. PHASE LOK V HEAD BOX ASSEMBLY: DESIGN, OPERATION, ALIGNMENT AND MAINTENANCE Richard L. Anderson Broadcast Electronics, Inc. Quincy, Illinois I. DESIGN The design of the Broadcast Electronics Phase Lok V Head Box is the result of several years of extensive research and testing to obtain the ultimate device to accurately adjust and maintain tape head alignment during the most rigorous use possible, 100% duty cycle in a radio station studio. The Phase Lok V micro-adjust head box is a completely removable unit that can be mechanically and electrically aligned and installed on any Broadcast Electronics "C" series deck without further adjustment. Two (2) hardened and ground dowel pins accurately locate the head box assembly onto the deck plate. Two (2) socket head cap screws secure the assembly to the deck plate. The Phase Lok V Head Box Assembly serves as the positive stop for the tape cartridge. It accurately locates the cartridge in the fully inserted position with relation to the capstan shaft, pressure roller and tape head penetration per the National Association of Broadcasters standards. * NOTE, other deck components serve to position the cartridge to the right and downward position - to be explained in "Cartridge Guidance System", a section of the previous paper titled: "TAPE CARTRIDGE TRANSPORT SYSTEMS: DESIGN, OPERATION AND MAINTENANCE" By Jeffrey H. Steinkamp, P.E. The following listed features are the reasons we feel the Broadcast Electronics Phase Lok V Head Box Assembly is by far the most rigid and maintenance free assembly used on any tape cartridge machine to date. 1. Frame: The main frame of the Phase Lok V Head Box is made from an aluminum alloy (6063-T6) custom extrusion that is precision machined to very close tolerances to insure interchangeability and stability. The surface is brushed finished and hard anodized per MIL-A- 8625 for a rich, appealing and very durable finish. 2. Head Mounts: The left and right head mounts are made from investment cast 380 alloy aluminum. These castings are precision machined to very close tolerances. This insures accurate positioning of the tape heads within the Head Box. The castings are brushed fin- ished then hard anodized per MIL-A-8625 for a very durable and appealing finish. 3. Dual Locked Three (3) Axis Adjustments: Each head mount is suspended in the frame by three (3) socket head die screws, three (3) very stiff compression springs and three (3) special cylindrical adjusting nuts. This allows the tape head to be adjusted smoothly thru all axis, Height, Zenith and Azimuth. Each head mount has two (2) lock screws. One (1) screw locks the Height and Zenith and one (1) screw locks Azimuth. This locking system insures head stability over a long period of rigorous use. 4. Tape Guides: The two (2) tape guides are a one piece non-magnetic (.050" THK) stainless steel stamping. The tooling is a custom permanent die set to insure an accurate part. The high luster finish is accomplished by the Electro-Polish process to insure a very smooth surface for tape contact. The guides are mounted in the frame so no screw heads contact the tape cartridge or in no way can the tape cartridge contact the tape guides or tape heads, thus preventing the adjustments from being destroyed during operation. 5. Single Tool Adjustments: One tool fits all. BE furnishes a screwdriver handled ball nosed hex wrench (BE #710-0239) to make all Phase Lok V Head Box adjustments. These adjustments are all located with free access without removing any other component except the top desk cover. II. OPERATION The Phase Lok V Head Box is simple yet ultra-precision in operation. The unique three point suspension system of the head mount allows the tape head to be adjusted thru the Height, Zenith & Azimuth axes with a smooth yet positive action. The three very strong compression springs mounted between the tape head mount and the head box main frame exerts a holding force of approximately 45 lbs. on each head mount to insure a stable setting of each adjustment. The three head mount adjusting screws are precision tooling screws that are inserted into countersunk pockets in the main frame. These pockets serve to keep the head mount centered within the assembly. The three compression springs are mounted into pockets in the head mounts and the main frame to allow the adjusting screws to pass thru the center of the spring thus putting the holding force of the spring in the force line of the adjusting screw. The cylindrical nut that is attached to head mount adjusting screw also seats into a half round groove in the head mount. This cylin- drical nut and half round groove allows the head mount to be rotated without binding during adjustment. Two oval point set screws serve to lock the head mount adjustment in a very positive position, thus eliminating any need of further adjustments, unless a head needs to be replaced for some reason. The two single piece tape guides are mounted to the inner surface of the vertical legs of the main frame by two (2) 4-40 screws each. This allows easy access for tape guide adjustment if needed. The tape guides are mounted so that no contact by the cartridge is possible, thus preventing any damage to the tape cartridge or tape guide adjust- ments. The tape heads are securely held in place by a cup point set screw. This screw is located in the head mount so the pressure is directly over the printed circuit board in the tape head, thus preventing any damage to the head should excessive force be applied to the set screw. The locating of the tape head in the mount is accomplished by fully seating the tape head into the mount and tightening the set screw to hold it in place. In summary, the Phase Lok V Head Box represents the extra effort Broadcast Electronics has gone to in offering the Broadcaster the very best in tape handling equipment. III. ALIGNMENT The alignment of the Phase Lok V Head Box includes track Height, Zenith and Azimuth of each tape head and the tape guide height (see Figures 1, 2 and 3). All adjustments should be made using Broadcast Electronics com- bination tape head, tape guide and motor gage #300-0002 to insure the ultimate in machine performance. A. Loosen the Height/Zenith and Azimuth lock screws turning them counterclockwise approximately one full turn (see Fig. 1). B. Position the head alignment end of gage 300-0002 against the front of the tape head. Turn the Height/Zenith adjusting screws as needed to align the top edge of the upper pole piece with the top edge of the gage. These adjustments should be made in alternating steps to keep the head movement to a mini- mum. C. Check Zenith adjustment and adjust until front of tape head is parallel to the front of gage. D. Repeat B and C until both Height and Zenith are correct. Tighten the Height/Zenith lock screw slightly to stabilize the head mount during Azimuth adjustment. E. Recheck B and C, make corrections if necessary. F. Make rough Azimuth adjustment by turning Azimuth adjusting screw to bring the head mount parallel to main head frame. G. Repeat for the other head. H. To align the tape guides, loosen the two mounting screws lo- cated on the side of the main frame (see Fig. 3). Insert the tape guide gage 300-0002 into the tape guide. Check to be sure that the gage is flat on the deck surface. While holding gage firmly in place, alternately tighten the two mounting screws (see Fig. 3). Check to see that the inside edge of the upper guide finger just contacts the top edge of the gage. Repeat for other guide. CAUTION: Misadjustment or worn guides will seriously affect stereo phase performance and damage valuable tapes. Check the tape guides and tape heads for indications of wear and replace as needed. I. Head Azimuth should be made using the alignment procedure outlined in the Technical Manual of each particular cart machine. J. The final step is to tighten the Height/Zenith lock screw and the Azimuth lock screw while the machine is connected to the various test equipment. NOTE: Make special note that no change in readings or measurements occur. IV. MAINTENANCE The Phase Lok V Head Box is without a doubt the most maintenance free head box design used to date. The only maintenance required is periodic cleaning of the tape heads and tape guides with a Q-tip moistened with isopropyl alcohol to remove any tape oxide. Then wipe dry with a dry clean Q-tip. Regular inspection and cleaning will prevent faulty recordings and damaged tapes. The extra care taken to properly align all individual components within the tape path will produce the best in frequency response and phase stability. The Phase Lok V Head Box will maintain that stability if properly aligned and maintained. ACKNOWLEDGEMENTS A special thank you to Kathy Klingler for word processing, Jeff Houghton and Bill Glore for the illustrations and Steve Ford and Jan Vance for publication assistance. THE AUTHORS Jeffrey H. Steinkamp earned his BSME from the University of Illinois in Champaign, IL. Mr. Steinkamp is presently serving as Manager of Mechanical Engineering for Broadcast Electronics, Inc. in Quincy, IL. He is a registered professional engineer in the states of Illinois, New York and Texas, and is an active member of the National Society of Professional Engineers. Richard L. Anderson attended Bradley University in Peoria, IL. Mr. Anderson is presently employed as a Mechanical Designer for Broadcast Electronics, Inc. in Quincy, IL. He has specialized in professional cartridge machine design for 25 years. He is a certified manufacturing engineer charter member, by The Society of Manufacturing Engineers. He is a 4 year graduate Tool & Die Maker from The Caterpillar apprentice academy and is certified by the State of Illinois as a Class A tool maker.