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The camera Marconi MkIII

David Petrie writes:-

Hello Brian Summers

Having looked at your website for the Museum of the Broadcast TV Camera I was interested in your comment about the left-handed 'beer handle' for the Mk3.

I attach a very poor quality picture of such a beast, although I have no idea how it was achieved - all the mechanism and tube were on the right-hand side - and any transverse shaft would have impeded the viewfinder movement.
I am familiar with the layout, as I operated this type for quite a few years, heavy beast that it was. A couple of comments may be amusing. Marconi in their wisdom, provided a 'dustbin lid', a black metal rubber edged bung to stop up the tubehousing, presumably to keep dust out when not in service, but they tended not to be used at all.
Hence, inserting the bung when de-rigging could provide some amusing moments when next the camera was rigged. Racks operators and engineers were generally not amused after the fruitless efforts to find the 'electronic' fault!

The ND filter, in service parlance 'The Wedge', was a two stop range and normal practice was to set it half-way in its travel and then set the manual irises, thus giving a crude 'stop either way' degree of control. This was fine until you had to start swapping the waterhouse stops used on the folded 25" and 40" OB lenses. Try that in a howling gale on a 100 foot scaffold tower when the light suddenly changes and the racks guy needs more light. The Mk4 was a welcome relief with its iris motor, however you will find that the original Mk4 had a Marconi badge on the nose of the iris motor and in later versions it was replaced with a large rubber bung. This was to allow the operator to free the jammed iris motor when all four lens irises failed to rotate in sync. or their clutches jammed. The method used was to try to rotate a knurled knob situated on the end of the motor shaft, the problem being that the motor was still trying to push the shaft around and when freed could almost take your fingers with it.

Your comments about safety when attempting to restore old gear, the dangerous voltages etc.remind me of a couple of things. We were required on occasion to operate in negative mode, this entailed pushing a button on the back of the head amp. and then to reverse, pull the button out again. I was never convinced by the assurances that there were no stray high voltages floating around on the back of the tube, generally the camera was on-air when the switching was needed, so you had to reach in down the end of the tube housing, not able to pull the tube up towards you (defocusing the camera), all a bit dodgy.

A colleague found-out one day that even with the covers on it still could be a dangerous beast. The small door on the rear that covered the talkback controls, in its open position, allowed a convenient ledge for keeping a pencil, he was returning his pencil (silver propelling type) to it storage position when he managed to insert it into the live pin of the F&E mains socket, ........noise on transmission was always frowned upon!!

I will be interested to follow the progress of your website and any acquisitions. Sadly I have no spare camera channels or even bits of spares, so much was just junked or in the case of our Mk 3s, sent to Durham University. I suppose it never occurred to anyone in charge that perhaps this was a valuable resource and image orthicon tubes etc.may one day be sought
after.

Best wishes
David Petrie