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 Avoiding Clogs Title

 

The purpose of this series of articles is to help you, the broadcast and professional videographer, maintain problem free recordings at minimal cost. Camcorders and other video tape recorders are electromechanical devices that need regular scheduled maintenance. Your true cost includes not only maintenance, but costs caused by a lack of preventive maintenance. Downtime, emergency rentals, re-shoots, and possible client loss, can cost more than a comprehensive preventive maintenance program.

I want to focus on video head clogs which inevitably happen to all VTRs. Video tape heads develop a buildup of material that will eventually decrease the head to tape contact and result in partial or total loss of RF signal recorded on tape. Playback of recordings with low RF signals shows up as a higher number of dropouts, video break up, or color problems. Predicting exactly when a head will clog is nearly impossible. There are too many variables in the recording process that contribute to the cause of head clogs; humidity, temperature, tape formulation, and VTR condition, to name a few. Frequent head cleaning is still the best insurance and least expensive preventive maintenance that you the videographer can do.

There are two types of deposits, each requiring a unique cleaning technique to remove. The first and most common deposit is a buildup of debris on the head that usually comes from the tape or the environment. This buildup is easily removed with the appropriate cleaning fluid and a lint free cleaning cloth. The second type of buildup is more prevalent with Betacam SP camcorders than with other types of field and studio VTRs. These internal VTR decks have smaller video drums with heads that spin faster and have greater tape wrap than conventional VTRs. This design difference results in higher head tip temperatures that literally "bakes" material on to the head tips. Eventually, buildup of this type of deposit will result in a poor recording. This phenomenon shows up more frequently on camcorders that use metal tape. Oxide tape use, because of its higher abrasiveness, results in less of this "baked-on" type buildup. The problem with this type of deposit is that it cannot be removed with standard wet cleaning techniques; only a head cleaning tape will remove these deposits.

To Minimize head clogging, try the following:

a) Begin a regimen of proper deck and head cleaning. Blow dust from the tape transport with a pressurized aerosol duster. Use a BCT-5CLN head cleaning tape on Betacam SP camcorders to remove baked-on deposit buildup. Wet clean the tape path of VTR and video head drum with 99% isopropyl alcohol and a lint free cleaning cloth. As a starting point for cleaning intervals, wet clean every 20 hours of tape time. Use a cleaning tape every second wet cleaning, or each 40 to 50 hours of tape time. FOLLOW CLEANING TAPE INSTRUCTIONS! Never play the cleaning tape for more than five seconds at a time during each cleaning interval. Cleaning tapes are very abrasive and will wear down the heads prematurely if used incorrectly. In this case, more is not necessarily better.
b) Find a qualified maintenance engineer who uses a head tip inspection microscope and have your deck professionally inspected and cleaned every hundred tape-run hours. This inspection will assess how effective your cleaning routine is. If there is no sign of " baked-on" deposits cut back on using the cleaning tape by increasing the intervals between head cleanings. While your camcorder or VTR is in for professional inspection and cleaning, have the video head tips measured for wear, the tape tensions checked and pinch roller inspected and replaced if worn.

c) Even though field recorders have an RF loss warning detector to alert you when a head is badly clogged, partial head clogs may not be detected. To catch these while shooting in the field, check playback in the viewfinder regularly. Besides the normal luminance (B/W) playback, check the color video signal by depressing the CTDM button. Luminance and chroma signals in the Beta format are recorded simultanious on two separate tracks. Marginal or no RF signal on the tape will playback in the viewfinder as noisy video that breaks up in the normal or CTDM mode. Look for a higher than normal drop out count as an early sign of a partial head clog. With camcorders you must stop recording to check the playback. On decks equipped with confidence playback capability you can check the tape playback while the recording is in progress by using the RET (return) button located on the camera lens.

d) Use "VTR save" mode as preferred mode of operation. Needless head spinning while in contact with tape not only adds to debris buildup but decreases video head life.

e) If you have a separate field deck, spot check your tapes throughout the shooting day. This procedure will not only show head clogs but also other problems that could occur with either the camera or VTR.

f) If you suspect problems with the tape stock, put a sample recorded tape aside and inform your maintenance engineer and tape manufacturer representative. Tape companies welcome and need your feedback if you experience problems with their stock. A suspected bad batch of tape can hurt the reputation of a normally reliable product.

The cost of a proper cleaning and maintenance program is an investment that pays great dividends. 
 

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