UNDER CONSTRUCTION
Meeting on 25th October 1961
Present: Frederick Bentham (FPB), Len Leggett (LL) of Strand Electric.
Demonstration of the LC/SCR system and discussion about the new SCR technology for TV Studio Lighting Engineers.
Audio Recording – coming soon
- Part 1
- Part 2
Transcription
FPB: Well I think we may as well make a beginning. And in welcoming you here today I may tell you I wouldn’t be in my shoes for all the tea in China. It’s awful lonely up here, and I’m really rather wondering what we’re going to show you, and what we’re going to tell you. Of course, this is not a meeting arranged to sell anything – that, we don’t go in for. The whole object is to provide you with an excuse to get together and meet your old pals, and it’s very often very difficult to find……. [6 seconds missing]….. what we thought in this instance we would use this meeting as a sort of target date to ensure that we carried out certainly experimental work and got it done in a reasonable time. So some few months ago we said on the 25th, largely as it was two days after my 50th birthday, that we would have this meeting and we would show you as far as we’d got with SCR*s. I don’t mean SCRs as we showed them a while back, about 20 months ago I think it was, something like that – I mean, in producing a production model. What we wanted to show you was something which could be ordered right away or as far as we’d got towards an equipment which might be ordered right away, not the same thing at all. It was thought that if we found that all one had as a result of SCRs was a smoking ruin with black smoke pouring out, then you should know about this, because it might act as a warning. At the same time, if you had loud knocking noises, from [….] because you were using SCRs then you should also know about this. Or if the Police turned up to say you were interfering with the television and radio in the neighbourhood and must switch it off, again it would be just as well for you to know about this. So what we’re going to do is quite an honest demonstration of what we have done so far and in particular, I’m going to call upon Mr Leggett in a little while’s time, to tell you how he set about it, and quite honestly, how far he’s got. But I want you to remember that this is not just a laboratory experiment – what we’re trying to do is to be able to launch an SCR control of 220 volts upwards, remembering that in America of course it’s always been done on low voltage, not the same thing at all. At the same time, one’s been trying to bear in mind that of course such a system should be within financial reach. Now it does appear that any SCR system at the moment tends by itself to cost much more than the systems which we will be putting in at the moment. The various components obviously will descend in price as their production for these higher voltages over here becomes more prominent. But at the moment, it’s not the cheap control, nor is it the small control. Because as Mr Leggett will point out, it tends to breed all sorts of ancillary gadgets and although one can wear the SCR as a decoration on the watch chain, there’s a hell of a lot of other stuff which needs a small pantechnicon alongside you see. The first thing is, why should one bother about SCRs at all. They happen to be there and it’s a possible form of dimmer. But I myself have always believed one shouldn’t allow the dimmer to design the control for one. One should aim at the control you want, and then apply a suitable dimmer to it. But there are certain defects with our present dimming system, as I’m only too well aware. And I don’t refer to the bits that fall off or things that go pop or things that fail to function and that sort of thing – they’re natural hazards of any piece of equipment from a motor car to a television set. Those things happen today and really are not necessarily related to a particular system. I want to treat today as if all things were perfect and therefore treat it on its’ theoretical merits.
I’ll have another drop of this muck. If it’s come out of the right tap, all will be well. If it’s come out of the wrong tap, I shall be laid low within the half hour. Only taps with the word ‘Drinking’ may be used to draw water but as the other taps haven’t got ‘Non Drinking’ against them sometimes one gets water out of them as well.
Well now, to return to the basics here, why should one bother about SCR. Well, of course, the Americans are at it and there’s been an immense amount of publicity. Very much [….] all the time. We heard and discussed, in this room, did we not, some eighteen months or whatever it was ago, this claim of decentralisation – the claim that the SCR provided a dimmer which would go in lanterns, and you therefore didn’t need the dimmer pack. And the next thing was you didn’t need patching – why the hell that [….] I couldn’t see. And then of course if you didn’t put it in the lanterns you put these SCRs up on the grid or hang them on the bars where if they went wrong during the show you couldn’t possibly get at them. And if they went wrong rather excitingly they would fill the studio with smoke – there seemed to be no reason for this decentralisation. Now I find myself approaching the notion, and regarding the SCR with favour because I have detested all other forms of all-electric dimmers so far, and maybe the newcomer might ultimately have some of the advantages not possessed by such systems as thyratrons, as saturable reactors and so on. In particular of course, as you will know, all my own work and thought on control is devoted to the notion that if we use a mechanical system we at least do not have to activate the control all the time and therefore one can conceive lighting in terms of change, rather than in maintaining a large number of combinations; and it’s the large number of combinations that lead to these multi-preset boards which I personally detest so much.
Now, on balance, it seems to me at the moment, and I still think applies for a little while yet, on balance, a mechanical system offers these wonderful advantages of what we call, rather incorrectly, inertia. And this enables us to approach the control with a freedom of design which doesn’t breed the multiplicity of levers. This linked with the notion of the memory action which enables you to pull out the groups you want to work on at the moment, it seems to me when the judgement day comes, it’s the one thing to lay to our credit with this approach to television lighting. But there’s one thing we can’t do with these inertia systems and that is we can’t cut the levels without some intensive pre-planning [….] You’ve got to [….] think out, and get the dimmers to the levels you require before you can go and suddenly activate them and bring them in to those levels. Furthermore, if circuits are at certain levels and you want to change them to another certain level, there’s a limit to the speed you can expect the dimmer to get there. We aim at a fast speed of about three seconds as you know – in theatres we go higher than that but with television we think it’s dangerous because of the tendancy for the dimmer to hunt, even at three seconds. At faster speeds it hunts even more. Then again it’s not possible to get accuracy of course if the dimmer is driving up this way or that way, maybe we don’t get to the same mark. Of course, we don’t. The polarised relay can’t be too precise otherwise again hunting will arise. But on balance it would seem that the mechanical system has it hands down at the moment and the frantic goings on ditching one system of all-electric for another that has gone on in America in the past twenty years would seem to endorse this – they have not been able to find the correct all-electric dimmer let alone the correct desk to control it from. If you consider that they were using saturable reactors in the early ’30s and then they controlled the saturable reactors with […] thyratrons with feedback circuits to improve the saturable reactors performance and this went on for a fair time, they then went into what the Ward Leonards called the Hysterset; the saturable reactor form shunted with half a valve circuit and then after that they went into direct thyratrons – they burned their fingers there – and then there was the magnetic amplifier range and then the magnetic amplifier range is replaced by the SCR […] at the moment. In our case, the dimmer we use was invented by Mr Mansell, whose picture is on the wall on the left upstairs, and he invented it in 1928 and we’ve been using it ever since, with minor improvements perhaps. But it means one has spent plenty of time thinking about the control rather than about the dimmer. However, the time has now come for a bit of a change, and to lead into what Mr Leggatt will tell us I think we’ll have one or two slides. I’m very fond of slides.
Now, one of the advantages of being an electrical firm like Strand Electric is the vast resources you have at your disposal. You have factories, experimental staff, maintenance staff and so on, and finally you have a contracting department who’ll do all the wiring for you. Unfortunately it seems that all of these departments serve everyone else except for Strand Electric and therefore it would be an advantage if we had […] made for us by someone else. It’s been very difficult to squeeze it into our own factories and in particular, with all due respect to our […] and splendid contracting department who serve others so well that they like us – and that makes me think the other contractors must be terrible – they are, when they come here, are constantly in the state where you can find the gentleman doing the wiring have vanished to go and assist some customer in his troubles. Thus it is that the gentleman who design the decor outside found he was held up and only saw what it looked like finally last night at about nine o’clock, where there’s other gentlemen who design decor have our contractor going backwards and forwards while they change their mind about the lighting, try this, try that, put back the original and all the rest. Here, it’s you’re lucky if you get it up. In fact when this theatre opened the only way we could get the house lights on, I’m now talking about nine years ago, was by putting one wire down to the radiator on the corner on the left. We have since found out how to do it properly of course. Now this, I’m leading up to the wild scramble has gone on to stage todays’ show and I think we should bear in mind, and give Mr Leggett a bit of sympathy in this, in that really he will be testing it as we go along this morning. So we’ll see what happens. I’ll open with the first slide, I think, Paul. Err a drop of focus.
Now we were going to show you very proudly and say that’s what the theatre looked like some two weeks ago. Unfortunately that’s what it looked like last night at about five o’clock. You see, in order to get our cables made, we had to make them ourselves in the technical department here – all our benches and jigs made up, and the stage floor, mercifully, is at bench height so we were able to use the front bit as you see. This machine I was determined to have modded in a peculiar way so now I’ve tried to play it I rather regret it. So all this is opened up and that’s as it was then. Next. Here’s another view you see, of the scene used as a workshop. As time went on it got worse and worse and anyway we finally got the thing cleared this morning. And there’s goings-on in the dimmer room – a tremendous help, and you’ll find that even now when you visit the dimmer room the lighting switches are very mysteriously placed up in the ceiling – you have to get on a ladder to switch the dimmer room lights on and off. So that’s not because we think it’s a good idea but because the tube carrying the previous lighting switch the simplest thing seemed to be to bend it up at right angles out of the way anyway that’s bit tidy now and you’ll be welcome to go and see with […] up there when the time comes. Right. And there’s the Showroom, so-called, as it’s moving on. Right, Next. This is a splendid picture and illustrates something – I cut it out of the Daily Express which featured it two weeks back and it’s the control in the Mermaid Theatre, London. Now either it illustrates that our control is jolly easy to operate, or it can be maintained by anyone, seeing that this particular gentleman hadn’t had much practice of late. Right, Next. Now what I wanted to just recap and remind you was that All-Electric systems do breed the Multi-Preset system and therefore in any pursuit after the SCR once we consider number one classes installations, as distinct from number two, by that I mean the smaller studios are at number two alas some of the provincials, not of course Granada or some of those – they are not number two class – and there are really two classifications. The one class, the second class, you might consider you could do fairly easily with comparatively simple one-preset control desks. When you want the first class thing at the moment we have to go to the Console with stop keys or some form like that. Now in America of course the number one class go into this Multi-Preset system which is a one set of levers and I’ve said this in this place on more than one occasion so I won’t go into detail – one set of levers here with every lever repeated ten times over there for ten presets. And there work has always been on this line and this is all very well when you’ve only got 40 dimmers. Next. But as you see when you go to 100 this thing gets very large indeed. And you’ve got to remember that this is what this man is using in the position of one of your controls – he has 100 circuits on here and he’s got his presets in these duplicated levers round there. […] the point I can’t help mentioning because it illustrates how one can fault control if you don’t go into detail – these are little wheels which move past an aperture and in consequence to track them from 0 to 10 that is from 0 to Full, you’ve got to move them three times, because only part of the wheel sticks out so to clear this down you’ve got your 100 times 10 you see and then you’ve got to do three operations on that and if you’ve got slide rules and enough light you can work out the answer. Right now, Next.
MORE TRANSCRIPTION TO FOLLOW
*SCRs are Silicon-Controlled Rectifiers
UNDER CONSTRUCTION