Letter: Mercury arc – the facts

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Sir,

Having been a projectionist at The Picture House when the mercury arc rectifier was in use, I was interested by the Courier article about it last Friday.

While this apparatus could help to keep the speed of the projectors at a constant speed (24 frames per second) the projector mechanism itself served that purpose.

Its function was to power the two projectors’ carbon arc lamps.  These wouldn’t work on alternating current, so the rectifier was needed to convert the incoming power from 240 volts a/c to 110 volts d/c and maintain it at that level so that there were no fluctuations in screen brightness.

The cinema stopped using carbon arc lamps after the ‘long-runner’ film delivery system was installed in the 1980s.

To run the film in a continuous strip rather than separate reels wasn’t possible with carbon arcs, as the carbons had to be changed so frequently.

It was also party because the copper which sheathed the carbons became prohibitively expensive.

In common with many other cinemas, the Picture House installed, along with the long-runner, a xenon lamp which was able to run continuously for long periods.

I congratulate the Campbeltown Community Business on the wonderful transformation they have made to the grand old lady of Hall Street.  It truly is magnificent.

But I wish they had simply disposed of the mercury arc rectifier.  It’s not a thing of beauty, and those of us who had to work with it ‘back in the day’ remember it as horrid and noisy. Quite simply, we hated it.

Far better they had put the money spent on restoring and displaying it towards a fully-operational screen curtain, thus enabling a return to the standards of showmanship we enjoyed in the cinema’s heyday.

William Crossan,

Campbeltown.

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