Origination Formats and Machines - 3/4" U-matic transfers

3/4" U-matic transfers

The Sony BVU-800 is a 3/4" U-matic tape machine originally designed for the broadcast market. Industrial models have part numbers that begin with "VO," the most popular models are the VO-5850 and VO-5800.While Sony also made many U-matic models for the industrial market, the broadcast models are preferred because of two significant differences. First, Sony added a visible head switch glitch in the output of the industrial U-matics. This head switch looks like 4 lines with skew errors at the bottom of the image. Also, the industrial U-matics may exhibit vertical picture rolls if address track time code is present on the tape, although an engineer can correct this.
 

U-matic machines have a BNC for video out. U-matics also have a U-matic dub input and output connector for video, essentially a precursor to the S-Video connector introduced with Hi-8 and S-VHS. This connector separates the luma ("Y") signal from the chroma ("C") signals, providing a quality boost for transfers from the BVU-800 to equipment that also has dub connectors. Usually that is another U-matic tape machine, although some TBCs have a U-matic dub input. It's important to note that while early JVC S-VHS machines used the same connector for the S-Video signal, these two signals are not the same.

The BVU-800 has XLR audio connectors. The audio output is +4 db, and will be compatible with broadcast recording machines.

Transferring U-matic tapes is usually straightforward, but Problems can occur. A very early U-matic tape that we were trying to transfer played perfectly for five minutes of the 30 minute program, and then began to rewind. After trying a test tape to verify that the tape machine was working correctly, we looked at the tape at that spot. You can access the tape on a cassette with a little trap door button somewhere near the front of the tape. I was worried that the tape would be crinkled or twisted at that spot, and not proceed along the tape path. What I found at that spot was clear tape; the magnetic material had stripped away from the tape for about a quarter inch.

What we were experiencing was the successful functioning of the auto rewind feature on the tape machines. A U-matic tape is normally clear for the last few inches, where the tapes is attached to the cassette reels. The U-matic tape machine has a sensor which identifies the end of the tape; it consists of an infrared light on one side of the tape path and a mirror on the other. When the infrared "sees" the mirror, it knows it is at the end of the tape. In our case, the transparent area on the tape was sensed as the end of the tape.

To play the entire program back we placed a piece of opaque tape over the infrared light sensor. As long as the tape was in place, the light would never "see" the mirror. We removed the top of the machine in order to carefully monitor the tape progress during playback, because we had disabled the end-of-tape function. With this function disabled, the machine could pull the tape right off the reel at the end of the tape.

Time code signal on U-matic tapes is a variable. Not all U-matic tape is time coded. If time code was recorded in the field, it was recorded on the address track, a digital track that shares tape space with the video signal. If the tape was post-coded, the time code was usually on one of the audio tracks, typically track 2. Eventually, Sony marketed a modification to BVU models that added a switch - audio 1, audio 2, or address track. With this, the time code on the tape can be read regardless of where it was recorded.

If time code is being transferred with other signals, it should go through a time code reshaper. This device guarantees that time code will have the proper waveform and thus, will be read correctly. At BAVC, the time code generators in the facilities control room which houses the remastering center are used to regenerate and reshape time code from U-matic tapes. This may not be as much of an issue as time passes.