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Broadcast facilities suite - Machine room

What else did you expect to find in the basement? If you wanted broadcast-quality television recordings in the 1960s you needed big recorders, which were often relegated to a machine room somewhere hidden away in the depths. Here, the machines and their technicians could be left to look after each other, seeing the outside world only occasionally but communicating with it all the time via the mass of cabling under the floor.

The Quadruplex VTR

Television had been on the air for decades before an effective electronic means of recording the programmes was developed. Compared to sound recording, which was widely used by broadcasters, the sheer amount of information encoded in a television signal had been an insurmountable obstacle. Transmissions were therefore either presented live, or shot on cine film and broadcast by running the film through a telecine machine, which scans the images from the film in real time. In 1956, however, Ampex made the breakthrough and demonstrated the first really practical broadcast-spec video recording system, using a 2-inch tape format which came to be called 'Quadruplex' on account of its four video heads. The quadruplex (or 'quad') system reigned supreme for broadcast use until the 1970's, when it was overtaken by smaller, more user-friendly and versatile formats. It really was a triumph of technological development to make video recording work in 1956. It required yet further skill and cunning to adapt the format for colour use during the 1960s. At this time the key rivals in the Quad arena were Ampex, the original developers, and RCA, who were first to build a colour machine. By the time of the format's demise, machines from both stables were fiendishly clever bits of kit with incredible precision and complexity at their heart. High-speed headwheels floating on air bearings, Nuvistor amplifiers, vacuum tape guides, servo systems optimised on-the-fly by analogue computers. And that is why, dear reader, you should never try to take a quadruplex recorder apart and put it back together.

RCA TR-70B Television tape recorder

This 1969 example belonged to a TV facilities company in London; it lived in their basement machine room along with many other video tape recorders of various types. By the late 1980s it was their last remaining quadruplex machine, because the quad format was effectively obsolete and there was little work for the old dinosaurs. When the company relocated to larger premises in 1989 a decision was made to decommission it and Lucien acquired it for preservation. The original intent had been to leave it behind in the machine room for one very specific reason; it was impossible to get it out whole. The shaft through which it had originally been lowered was now full of air conditioning plant and the arch in the wall it had come through had since been bricked up. The newer machines were smaller and lighter and all were successfully carried up the narrow staircase in pieces. The quad, naturally, wouldn't even go round the first bend in the corridor let alone up the stairs. 'You'll have to cut it up,' said Tim, its former guardian who had set Lucien on its trail in the first place. Naturally we looked at the alternatives: Dismantle and re-instate the air conditioning, knock the wall down, even push it out onto the fire escape and crane it over the top of the building. Nothing came in at less than a five figure sum, and it simply wasn't worth it. So Tim was right, and the TR70 was cut into small pieces in an afternoon using a hacksaw and cable shears.

Knitting

Knitting

NEVER DO THIS!

RCA presumably did not foresee the need to rip their products apart in a reversible way. Not only did they weld the whole frame together in one large inconvenient lump, they omitted to provide a comprehensive exploded drawing of all ten thousand parts of the main chassis in the seven volume service manual. Three serious mistakes occurred as a result of the pressure:

Equipment loaded into chassis

Equipment loaded into chassis

Monitor bridge installed

Monitor bridge installed

Upper chassis mounted

Upper chassis mounted

The machine was therefore reassembled as a static exhibit, and although Richard and Lucien spent some time on the wiring and got some functions working, the prognosis was uncertain and time limited. Recently it has had to be moved again, for which purpose it had to be taken apart once more. Curiously the situation no longer looks so bleak. With the wiring loom stripped out and everything cleaned up, one could almost imagine that it was in the assembly shop at RCA back in 1969, awaiting the next step.

A moment of traditional machine room humour

One of the trademarks of operational engineering departments in the broadcast industry was the burst of sophisticated technical humour that occasionally bubbled to the surface. Videotape operators would cut together outtakes or make animations, and we can offer our first clip in this tradition as a result of our painstaking reassembly of the quad. Watch video: TR70 gets its act together

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