Anonymous asked in Science & MathematicsEngineering · 1 decade ago

How much training was required to operate and maintain a 'quadruplex' videotape recorder?

How much did a Quadruplex VTR operator have to know to maintain those old videotape machines? I mean machines like the Ampex VR2000, AVR-1,or the RCA TR-70 vtr's? And what are some of the problems these machines had? These machines were the broadcast-standard VTR's for 30-some years.

2 Answers

  • lare
    Lv 7
    1 decade ago
    Favorite Answer

    not hard to learn?? Both Ampex and RCA had regular schools to train the television station technicians to repair these. There are a number of very complex sub-systems. First you need an external air compressor for these to operate. They also needed vacuum, but that was usually generated internally. The spinning of the quad head has to be sychronized with externally supplied horizontal, vertical, subcarrier, burst flag, and blanking signals. you will need a generator for these singals. The spinning head is a mechanical device so the recovered video signal is very unstable timing. This has to be corrected by the amtec, videotec and the colortec which switch timing loops in and out to keep precise timebase synchronization. The tape tension has to be manually adjusted to minimize venetian blind artifacts. It took about 20 seconds for these to get up to speed and sync, therefore the director had to call for them to roll 20 sec in advance. To be sure that the start of the video program matched the roll up time, a mechanical tach has to run against the tape. This allows the operator a means of mechanically back winding the tape to the pre-roll point (20 seconds at 15ips is 25 feet, hard to measure out quickly with a ruler) Quad did not make a picture in still or slow motion so the operator did not have visual cues (like a count down timer) for setting the tape position. These were mono audio on a linear track that ran at 15 ips (although some later models were "merlinized" to run at 7.5 ips and split head stereo audio). Ampex never understood how color video worked, but RCA ran the NBC network that depended on color. The record frequency chosen by Ampex caused a herringbone interference on the color subcarrier. RCA solved this by running the record carrier frequency up higher so that color quad machines were later known as "high band". Ampex traded RCA a manufacturing license in exchane for the color circuits. FYI you just don't stick video into a magnetic head and have it record. It has to first be FM modulated onto a highband carrier. Ampex was also very weak in transistor theory, which is why the first model was all tube. Ampex traded its patents on helical scan video recording to Sony in order to get a usable solidstate design. Helical scan was the basis of all the future generations of videotape formats. Getting parts for a product that was designed 50 years ago will be a challenge. If you can get a complete set of manuals, they will provide months of reading.

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  • 1 decade ago

    you say "was required" not "is required" so I assume you mean was required in the days these were in use.

    those days there was no formal training for these kinds of things. And to be truthful they are not all that difficult to operate. You would watch someone operate one for a while, read the manuals, and learn by doing.

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