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Eventually, everyone will experience video tape recording problems. Heads wear out. When and what to look for are the subject of this message.

When it comes to video heads, think of them like your auto’s tires. I recently replaced the tires on my SUV at 45000 miles, even though they were not worn out according to safety inspection standards. I did not feel completely safe driving on snowy roads with marginal tire treads. My preferred tank-like traction came back after replacing the tires. I valued safety over cost.

By understanding the headwear cycle you can prepare yourself for inevitable problems. Spinning video upper drums have a number of imbedded head tips that lay down the picture, sound and time-code information (depending on format). Head tips project out of the drum surface, and into the surface of moving tape stock. By design, these heads have a self-cleaning ability that is maximum when new. As the tip projection decreases, the self-cleaning ability is also reduced.

The second problem with worn heads is that the less head tip projection into the tape (head to tape contact), the poorer the quality of the recorded signal on the tape. The same applies to playback of a recorded signal. Dropout compensators, or error correction, can handle only so many signal drops before the picture or sound becomes unacceptable.

How do you determine when it’s time to replace your video heads? If you are diligent and check playbacks of your recordings you will sense the change in quality over time. With the larger Betacam heads, head tip projections can be measured. There is a comparison range of new head projections to worn out heads that will be a good guide on when to replace the head drum. Smaller Betacamcorder drums have new head projections of 18 to 21 microns, and are worn-out at about 9 microns. Larger Betacam head projections are 30+ microns when new, and worn at about 15 microns.

Smaller DV, DVCAM, and DVCPRO drums are not easily measured because of cramped transports and lack of proper measuring devices. The starting place or guide to replacement time can be found in the maintenance manuals for each video product. For example: BVW-D600 (Betacamcorder) 500 hours, DSR-500 & DSR-PD150 (DVCAM) 1,500 hours, AJ-SDX900 (DVCPRO) 2,000, and AJ-HDC27 (DVCPROHD) 2,000 hours. These numbers are recommended, however heads can sometimes fail sooner or later. Tape stock can vary in abrasiveness and tape transport tensions can increase over time, which will increase headwear.

Almost all video recorders have drum hour meters which should be checked periodically. It is always a good idea to monitor drum hours on your decks while looking for signs of problems. Check your operation manual for information on accessing your hours meter.

Analog video recorders show a more gradual deterioration of quality than do digital recorders. With digital error correction there is much less warning of up coming head wear problems. It is your individual choice to preventively replace your heads or wait until they fail. You have a choice of maintaining your gear or repairing it.

As I mentioned in my car story, safety and reliability were my main concern. I preferred safety above cost.

Take care,
Roger

 

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