Product Details
Sales & Support
Documentation & Visuals
(APPROXIMATELY 15 PAGES) ----CR-850U DESIGN OBJECTIVES----- The CR-850U is a very high quality 3/4" editing VCR with characteristics that make it suitable for a wide variety of applications. It was designed with the following objectives in mind: - it should have a picture reproduction quality second to none. - it should be easy to use - it must adapt to a wide variety of systems and applications - above all, it must be reliable The CR-850U achieves all of these goals and more. It incorporates a variety of innovations in VCR technology and will certainly set new standards of performance.
------------SIGNAL QUALITY, PERFORMANCE------------- The most important attribute of a 3/4" editor is its picture quality. Design engineers made every effort to see to it that the CR-850U would have absolutely the best picture reproduction quality of any 3/4" VCR on the market. And there's some pretty tough competition in front load 3/4" VCR's! JVC achieved this target using a variety of methods which included some new innovations. Most important, was the attention to detail paid through every step of the design/manufacturing process. An exhaustive quality assurance procedure was established to see to it that every unit matched the high performance standards established. HIGH SIGNAL TO NOISE RATIO Through the use of a variety of circuits, the CR-850U has exceptionally low noise--47dB signal to noise ratio in the color mode! And the less noise produced by a VCR, the cleaner the picture. This is especially important in the editing process, since noise is usually compounded as multi-generation dubs are being made. Here's a brief semi-technical description of some of the circuits used to keep the picture quality clean: - Direct APC for video. "APC" stands for "automatic phase control." This is the circuit which keeps the colors stable. Unfortunately, most APC circuits also add distortion (noise). Conventional APC circuits have two converters which process the signal, using a VCO (Voltage Controlled Oscillator) which is not very stable. JVC's new Direct APC uses a high frequency VCO (more stable), and only one converter to process the signal, resulting in much lower distortion! In the new circuit, the signal makes two passes through the VCO (double-loop) instead of just one. This results in a slightly longer color lock-up time than in the conventional circuit (0.3 seconds vs. 0.0 seconds). - E-E APC off. This feature improves the picture quality in the E-E mode. A logic circuit switches in the APC circuit only when required. - DC controlled preamp. This newly designed circuit reduces noise caused by resonance of the video heads and their associated wiring. - Separate channel FM Equalization. This feature compensates for frequency response differences between individual heads during playback. - Channel switching noise canceller. This feature removes channel switching noise, replacing it with a 1H delayed signal instead of the original signal at the switching point. - Sideband Equalization. The CR-850U employs "tearing" prevention circuits which incline the frequency response while maintaining flat group delay characteristics. These circuits eliminate tearing when very old tapes are played back. - Line correlation noise canceler. This circuit is employed in the CR-850U to reduce random noise. By comparing one horizontal line with the next, random noise is detected and reduced. The circuit decreases the random noise, cancels the chrominance carrier leak (improving the rising or falling edge of the signal), and cancels the 2FC beat. Line correlation is employed not only for luminance, but also for chrominance thus reducing chroma noise. - Current drive REC Amp for each channel. The newly developed current push-pull amplifier minimizes secondary distortion. A frequency response adjusting circuit is also provided for each channel, so that despite minor differences in head characteristics, the recorded tape will be uniform. - Time code noise canceller. Because of the location SMPTE time code is recorded onto the tape, interference can occur between the time code signal and the video signal. A "tank" circuit is used for cancelling the noise and avoiding impairment of picture quality. - Differential gain (DG) compensator. This circuit actively compensates for DG deterioration inherent in the recording/playback process. - Linearity correction. The demodulating circuit inherently has some non-linear distortion. This circuit improves linearity by applying opposite non-linear response. Even after several generations of dubbing, the picture will have little non-linear distortion. - Y/C delay adjusting circuit. This is a variable delay circuit for the chrominance signal. It is employed in 3 locations. Because of this circuit, the CR-850U has very little Y/C delay in every mode. - Improved drop-out compensator. Drop-out compensation is now placed after the FM (off tape) signal has been demodulated. This results in drop-outs being compensated for before they are actually seen in the picture. A more noise free picture is the result. Y-688 Dubbing System On a 3/4" tape, the video signal is recorded in form of an FM carrier signal, with an imbedded chroma signal at a much lower frequency (688kHz). In normal video transfers, the player converts the 688KHz to 3.58MHz and demodulates the FM to a luminance signal (Y). It then combines the 3.58MHz chroma with the Y signal and those eventually become the composite video signal, which is transferred to the recorder. In the Y-688 dubbing system, the conversion processes that chrominance passes through are eliminated. This method transfers the modulated luminance (Y) and the unconverted chroma (688KHz) separately, through a multi-conductior cable. The result is a cleaner transfer with less discoloration. The Y-688 dub signals and cables used on the CR-850U are fully compatible with the dub connectors used on the Sony BVU-800 and VO-5850. An additional benefit of having the Y-688 dub system is that the CR-850U will be able to take advantage of some of the high quality TBC's on the market, which use the dub signal, such as the Fortel Y-688 Error Corrector. Y-FREQUENCY RESPONSE CONTROL By controlling the level of the luminance (Y) signal in the 3 megahertz range, the picture can be made to look sharper or softer depending upon the subject material. This control, located on the front panel has seven positions (click stops) which either increase or decrease the detail seen in the picture. ---------CONVENIENCE----------- The CR-850U has a wide variety of features which make it not only flexible, but easy to use. Throughout the design process, careful attention was paid to human engineering. Despite the number of buttons, switches, and indicators on the front panel, operation is extremely simple--and for the most part, foolproof. VIDEO LINE INPUT BLANKING SWITCHER WITH REMOTE FUNCTION Besides the 7 pin dub input, there are two video inputs labeled "LINE A" and "LINE B". These inputs are selectable by pressing a pushbutton on the front panel. An LED lights to indicate which input is active. When switching from LINE A to LINE B, the CR-850U performs the switching in the vertical interval. If the signals are genlocked together, then the transition is glitch-free, even when it is recorded. To further this benefit, a connector is provided on the rear panel for remote operation of this function. Contact closure of this connector causes the VCR to switch from LINE A to LINE B. The VCR can actually be used as a "mini-switcher." This is likely to be very useful in a remote recording location where a minimum amount of equipment is desired. Where manpower is a limitation, the remote switching function can be used to allow one camera operator to switch to another camera while the VCR is unattended. BUILT-IN EDITING CONTROL FUNCTIONS In many instances, a separate editing controller is not necessary to perform editing functions. The CR-850U has a built-in Z-80 microprocessor which controls these functions. (This is the same chip on which many personal computers are based). A close look at the control panel on the CR-850U shows many of the same functions found on popular editing controllers: - PREROLL. When no edit entry point has been selected, pressing this button will back up the tape exactly 5 seconds. (This time is variable through DIP switch selection). If an entry point has been selected, the VCR will back the tape up to 5 seconds before that point--regardless of where the tape is when the button is pressed. It can also be used like a "GOTO" or "SEARCH" function, since the tape will always return to the same point. - PREVIEW. Pressing this button allows the operator to view an edit without recording the information on the tape. If any changes are required, they can be made before the original material is erased. - ENTRY IN, ENTRY OUT. Pressing these buttons marks the edit-in and edit-out points which are used in the editing mode. Once the edit points have been set, pressing the IN button or OUT button alone will cause the counter to display the edit locations. Pressing these buttons simultaneously will cause the counter to show the difference between these two times--the duration of the edit! - ASSEMBLE, INSERT. The type of edit can be selected using these color coded buttons. In the "insert" mode, control track is not disturbed, as flying erase heads are used to erase the video information. - EDIT START, EDIT STOP. Edits can be started either while the tape is parked, at which time the PREROLL mode is automatically entered, or "on-the-fly" while the tape is moving. If an edit has been started while the tape is already in motion, pressing EDIT STOP will only terminate the edit mode and will not stop the tape. This can be used to cut in and out of a running program. In some instances it is easier to maintain the program's continuity when editing this way. DIGITAL TAPE COUNTER The LED digital tape counter on the CR-850U displays HOURS, MINUTES, SECONDS, and FRAMES. Its count is based on the FG pulse from the capstan circuit, and will continue to read even if control track is lost. (Other machines stop counting when they run out of control track.) If the control track reference is desired, a DIP switch can be flipped internally to make this selection. In addition to displaying tape travel, the counter in the CR-850U has another function unique to a VCR: it has a built-in LAP TIMER. This is like having a separate tape timer working independently of the normal counter. It can be selected by pressing the "LAP" button on front panel, and deselected by pressing it again. The LAP TIMER automatically resets to 00:00:00 when an edit point is entered. It can be used to measure tape travel distance from the starting point. It is especially useful when doing fixed length edits. For example, you mark an in-point at 12:15:23 and you want to do edit which is exactly 5 seconds 16 frames long. On other VCR's (and on most editing controllers) you'd have to get out a pencil and paper to figure out where to mark your out-point. On the CR-850U, simply switch to the LAP TIMER after you have marked your in-point, and then move the tape to "00:05:16" and set your out-point. VISIBLE PICTURE SEARCH The front panel search dial on the CR-850U provides a convenient way to shuttle the tape with a viewable picture at speeds from 1/30th to 10 times normal in forward and reverse. In addition, detents are provided for 1X (play speed), 10X, and high speed (15X fwd, 20X rev). Note: speeds above 10X may be viewable on some high quality monitors. There is another characteristic of the search function worth mentioning. When the search dial is moved to the 1X (play) position, the picture can be viewed in much the same way as when the PLAY button is pressed, with one minor difference--the sync reference signal. In normal playback, the machine locks up to an external sync signal, or to an incoming video signal if those signals are available, depending upon the position of the front panel switch. In search dial playback, the sync reference is always the internal oscillator. Here's the benefit: If the incoming video is unstable as is the case when the source machine in the editing system is being shuttled, normal playback will also be unstable. However, if the operator chooses to play the tape with the search dial, the picture will lock up perfectly, no matter what the source machine is doing. Internally, the search dial is providing serial data to the CR-850U's command system. Unlike earlier JVC editors, the search speeds are now stepped at the following intervals (forward and reverse): 1/30X, 1/10X, 1/5X, 1X, 2X, 5X, 10X, 15X (fwd) 20X (rev) These search speeds apply, regardless of whether the VCR is controlled from the front panel, or from an editing controller. JOG MODE In addition to visible picture search, another function is provided, which can be accessed when using a serial editing controller. "JOG" is a feature which allows the picture to accurately follow the movement of the search dial on the controller, as it is turned to the right or left. To use this feature, the editing controller must also have the JOG feature. The jog feature is not available from the search dial on the machine. FULL CAPSTAN CONTROL IN ALL MODES When the cassette is inserted into the CR-850U, mechanism fully loads the tape around the head drum. The tape remains threaded in this fashion until the eject button is pressed. This permits much faster cuing times, as well as more positive control over the tape. A special "standby" mode is provided which stops the head drum and disengages the pinch roller after 10 minutes in still. This permits rapid drum-up to full picture while protecting the tape and vital components. LARGE, ILLUMINATED PUSHBUTTONS Tape control and editing functions are controlled by illuminated pushbuttons on the front panel. The type most preferred by professionals, these buttons are more expensive than typical pushbuttons, but lend themselves to heavy duty operation, and greatly reduce the chances for operator error. To further reduce the chances for a mistake, certain functions are color coded: Function Color Record red Play white Stop blue Eject blue Edit start red Video insert green Audio insert green Assemble edit yellow SEPARATE AUDIO, VIDEO/TRACKING METERS Illuminated meters are provided for audio channels 1 & 2 and for video/tracking. Next to each meter is a level control. For the audio channels, the knob is a concentric type with separate controls for playback and record levels. Playback levels can be adjusted without disturbing recording levels. The video/tracking meter serves two functions. During playback, the meter indicates the level of the FM carrier. Tracking adjustments can be made by turning the tracking knob to the right or left. During the STOP and RECORD modes, the meter indicates the level of the incoming video signal. This level may be adjusted with the video level control if the VIDEO AGC switch is turned off. INDEPENDENT AUDIO LIMITERS Besides adjusting the audio levels manually, the CR-850U can adjust levels automatically with its built-in limiter circuit. Separate on/off switches are provided for each channel, a JVC exclusive feature. Some users prefer to record with the limiter ON on one channel while recording with it OFF on the other. The best channel can be picked at a later time. The limiter automatically adjusts the recording level so as to prevent overload. It is normally switched OFF during the editing process. ELECTRONIC SKEW CONTROL To control any bending or flagging at the top of the picture, a skew control is provided. Skew normally occurs when a tape recorded on another machine is played back. Adjusting the skew control makes minor variations in the tape tension. Most 3/4" VCR's use a mechanical lever or knob to reduce skew error. JVC's electronic skew control takes advantage of the advanced tape tension system used in the CR-850U. It is much smoother and more precise that the mechanical controls. ----------FLEXIBILITY------------ It is fitting that an editing VCR as advanced as the CR-850U be able to adapt to a wide variety of systems and applications. For this reason, JVC incorporated a number of features which are explained below. FRONT LOADING DESIGN Besides saving space the front loading design permits mounting in a standard 19" rack, with an optional rack slide kit. All operational controls are mounted on the front panel. On each side of the CR-850U are flip up carrying handles for added convenience. SERIAL (RS-422) AND PARALLEL EDIT CONTROL CONNECTORS - SERIAL. A 9 pin "D" type connector is located on the rear panel for connection to editing controllers and other components. The RS-422 signal used by this connector is compatible with the Sony BVU Series. Using the serial port permits connection to a wide variety of sophisticated controllers. The serial connector will also be used for future JVC editing controllers. - PARALLEL. A 45 pin connector is located on the rear panel for connection to existing JVC editing controllers. Direct connection can be made to the RM-86U or VE-90AT/VE-93 controllers. SMPTE TIME CODE CAPABILITY SMPTE time code is a digital code which can be recorded on one of the VCR's audio channels, to provide accurate indexing of the tape and to provide an accurate reference for editing. Each frame of video is indexed with an 80 bit "word" of code which gives it a unique identifying number. Advanced 3/4" U-VCR's use a 3rd audio track, known as the address track, for recording time code. This frees up the normal audio tracks for their intended purpose. On the address track, the recording and playback circuits are optimized for the time code signal for better accuracy. The CR-850U is equipped with an address track for SMPTE time code. A front panel LED illuminates when a signal is present on this track. Inputs and outputs for this signal are RCA type connectors on the rear panel. To record time code, simply connect a time code generator to the input. Recording level adjustment for the address track is automatic. Advanced editing systems utilize time code extensively. Since each frame of video is identified with a code which is consistent from one machine to another--even from one format to another--editing costs can be reduced drastically, using "work tapes" (copies of the original masters), with less expensive VCR's. The time code track on the CR-850U is fully compatible with the Sony BVU-800 series. A 14 frame offset will be encountered when using tapes recorded on a Sony BVU-200 series machine, or the JVC CR-8250U. This offset may be compensated for with the JVC VE-93 Editing Controller, which will add or subtract the required number of frames. BALANCED XLR AUDIO Most professional audio (and video) equipment use "balanced" audio circuits. In a balanced circuit, the signal is carried in a cable through "hot" and "cold" conductors, along with a ground. These circuits are generally more immune to hum and interference, especially in high RF environments (like in broadcasting stations) and where long cable runs are used. The audio inputs and outputs on the CR-850U are balanced, and utilize standard 3 pin XLR connectors. The inputs can be switched for three levels, depending on the audio source: The -70 dB position allows connection of a microphone to the XLR audio input connector. This is superior to previous models on which unbalanced phone connectors were used. Audio output levels are switchable between +4dB and -20dB. An audio MONITOR OUT is also provides a signal selectable from the front panel--either AUDIO 1, AUDIO 2, or MIX. RF OUTPUT FOR EXTERNAL DOC A single BNC connector on the rear panel provides an RF output which can be used with an external drop-out compensator. External units can provide better drop-out compensation than available internally and some users prefer them. EXTERNAL SYNC & SUBCARRIER INPUTS For connection to a wide variety of time base correctors, inputs are provided on the CR-850U for external sync and subcarrier (SC). A selector switch is located on the front panel to switch between various forms of external sync. - EXT. The CR-850U will lock to the external sync signal applied to the sync connector on the rear, but if none, then to its own internal oscillator. In the STILL and search modes, the VCR reverts to its internal oscillator to maintain a stable picture. - VIDEO. The CR-850U will lock to the incoming video signal of the selected input, but if none, to its internal oscillator. - TBC. In this position, the sync reference is the same as in the EXT position. However, in the still and search modes, the VCR continues to reference the external signal to prevent vertical roll. SWITCHING REGULATOR POWER SUPPLY The CR-850U can adapt to a wide range of AC power sources: 85V to 135V, 50 to 60 Hz. (It also can be switched internally to operate from 170V to 270V.) The advance switching regulator power supply produces less heat and takes up less space than a conventional one. To further reduce heat, a quiet cooling fan is used. -----------RELIABILITY------------- One of the most important considerations in designing the CR-850U was making it extremely durable and easy to maintain. JVC engineers anticipated rough, continuous operation and built the CR-850U to take alot of punishment. Naturally any electronic component, no matter how well built, will eventually require maintenance. With that in mind, a number of systems were employed to assist in maintenance and troubleshooting. DIAGNOSTIC WARNING SYSTEM Advanced microprocessor technology was applied to a sophisticated array of sensors and detectors throughout the CR-850U. If a problem occurs within the drum servo system, tape path, loading mechanism, etc., the VCR will immediately detect it and go into the "warning" mode. All functions will immediately be terminated so as to protect the tape and the machine. When this happens, a digital readout on the front panel will display a code number from 01 to 99. This code number corresponds to the type of problem detected. For example, you are playing a tape and the machine suddenly goes into the warning mode. All functions are dead and the numeric code "03" is displayed on the warning panel. The operation manual states that "03" means that the built-in dew sensor is activated. There is probably excessive humidity in the machine or cassette, and it should not be operated until it is dry. In most cases, the warning mode may be reset by turning off the power to the VCR and then turning it back on. Before doing this it is wise to check the operator's manual for any precautions, to prevent damaging the tape or machine. FRONT PANEL TEST POINTS To aid in troubleshooting and preventive maintenance, test points were placed onto the front panel. A technician would normally connect test gear to these points and analyize the machine's performance. Adjustments can be made by opening the top or side panels. EXTERNAL HOUR METER On the rear panel, an externally visible hour meter reflects the amount of running time on the head drum cylinder. This is especially valuable in determining preventative maintenance schedules, cleaning, etc. FULLY DIRECT DRIVE TRANSPORT SYSTEM Direct drive motors are the most accurate, reliable way to move tape in a VCR. The CR-850U uses a fully direct drive reel servo system (separate motors for the supply and take-up reels), which keeps tape tension constant during all modes. There are no belts, pullys, or idlers to require maintenance. In addition, the head drum is directly driven by a servo-controlled brushless DC motor. Together with a servo-controlled capstan (also a brushless DC motor), it assures highly stable pictures as well as greatly improved reliability. DIE-CAST CHASSIS All critical components are mounted onto a heavy-duty die-cast chassis. This assures stability, even when the machine is moved around alot. Circuit boards are easy to access, and can be unplugged from the machine if necessary.
