Planning my Studio ‘E’ Rebuild In 2009, inspired by three things - finding some original components, buying a copy of Gilbert Davey’s first book, and reading a vintage radio forum thread – I decided to see if I could either locate a Studio ‘E’ leaflet, or failing that, come up with a reconstructed Studio ‘E’ design.   Now that a leaflet has come to light, this page is of course superseded.   I have retained it for the time being, so that all visitors can compare my conjectural efforts with the genuine design, and see just how far astray my well-intentioned musings led me!

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Circuit and components Early in 2009, I was going through various boxes of spares, and came upon several components that I knew came from the Studio ‘E’ one-valver built for me by my father (see MY ORIGINAL STUDIO ‘E’ SET page) and dismantled some time later.   I found the two variable capacitors, the coil, a DAF96 valve and valveholder, the original control knobs, and the 4-pin battery plug.   I also found a pair of brackets that my father had fitted to brace the front panel, and the switch that he had added in the LT supply (he had added the brackets and switch on his own initiative as extras to the design in the leaflet).   I set them all aside together.     The one-valver circuit and components list from     Fun with Radio, 1st edition, 1957.     Drawn by R Barnard Way; reproduced with acknowledgments to R Lawrence.   Other rights may subsist.     Image from site author's copy. Then I bought a battered copy of the first (1957) edition of Gilbert Davey's Fun with Radio.   It included a beginner's one-valve design.   Was this the same circuit as was used for the Studio ‘E’ series? At about the same time, I did an internet search, and came upon a thread on the BBC 1-valver on Paul Stenning's http://www.vintage-radio.net forum.   This had run from January 2005 to May 2008.   One of its contributors suggested that the BBC circuit might have been the same as that published in Fun with Radio, and another thought it could be related to a Boy's Own Paper design. I compared the circuit with the set of components I had picked out before I got the book.   That is, I did not take the easy course of looking for components to match the component values given.   Here’s what I found:

		Components specified in Fun with Radio, 1957 edition	Components from my original Studio ‘E’ set
		Valve DAF91	Valve DAF96 - see below
		Teletron D/R coil	Unmarked coil I knew to be from my original set - see below.
		C1 Tuning capacitor .0005μF	.0005μF solid dielectric
		C2 Reaction capacitor .0001μF	.0001μF solid dielectric
		C3 .0002μF	None
		C4 .1μF	None
		R1 2.2MΩ	None
		R2 10kΩ	None
		R3 .5MΩ	None

Another root around (with the circuit to hand) turned up a 2.2MΩ resistor with some vintage-looking sleeving, which might also have been in my original set.   I couldn't be as sure about this as with the other parts, though. My valve was different from the one specified, but I have since seen later editions of Fun with Radio in which alternatives including DAF96 are given.   I also think I remember that the same two valves were mentioned as alternatives during the Studio ‘E’ series.

The coil from my original     Studio ‘E’ set, with its three     wave-wound windings.

My coil has three "wave-wound" windings, with an adjustable dust-iron core, and a slotted circular tag-ring with six tags.   I have found no reference to the Teletron D/R coil on internet searches, but a visit to the vintage radio web site vintageradio.me.uk yielded details and a picture of a Teletron HAX coil.   The family resemblance between that and mine is unmistakeable, and my coil also looks like the one shown in the layout in the book   On my coil, two tags were connected together with a soldered wire link left in place when my original set was dismantled.   It had never been used for anything else.   Meter tests (after cutting the surviving wire link) confirmed that the tag connections corresponded with those shown in the book.   I guessed that the surviving wire link had been the earthed connection between aerial and grid windings.   If my coil is a Teletron, it would be a strong link between the Fun with Radio design and the Studio ‘E’ design. So, including the valve and coil in the above list, I had four key components from my Studio ‘E’ set that also appeared to suit the Fun with Radio circuit.   Admittedly, a.0005µF tuning capacitor and a .0001µF reaction capacitor were common values for many simple TRF circuits with reaction.   I do put more weight behind the valve and coil though. It’s also worth noting that the Fun with Radio circuit doesn’t feature a choke in the anode circuit (a very common arrangement for one-valvers), but relies instead on a 10k resistor and perhaps the “choke effect” of the headphones.   I am quite sure that the Studio ‘E’ design didn’t use a choke either. I concluded that the one-valver circuit as given in Fun with Radio was almost certainly the same as that used for the Studio ‘E’ one-valver, but only that leaflet can clinch it.   Although Fun with Radio was only published as the Studio ‘E’ series was being shown, the circuit must date from some time before then, to be available as the book was readied for publication.   Indeed it may have been available to Boy's Own Paper readers as a separate supplement - see DAVEY 1-VALVER HISTORY. Layout However, the Fun with Radio practical layout given alongside the circuit did not accord with my memory of my Studio ‘E’ set.   The differences were:

		Fun with Radio layout	My memory of Studio ‘E’ set
Chassis		Shallow 4-sided inverted tray. Hole drilled for valveholder. Front panel fixed to one flange of tray.	Chassis floor split transversely, on side runners. Valveholder and coil bridging gap in chassis floor. Front panel screwed to runner ends.
Component positions as from front		Reaction capacitor on left; tuning capacitor on right. Coil on left; valve on right.	Tuning capacitor on left; reaction capacitor on right Valve on left; coil on right (see below).
Terminals		On front panel.	At rear of chassis.
		Several contributors to the http://www.vintage-radio.net thread backed up my memory of this split chassis arrangement in the Studio ‘E’ design, and I am indebted to them.   The arrangement certainly has the virtue of avoiding the need to drill a large hole for the valveholder when a suitable drill may not be available, and also leaves useful spaces to lead wiring from beneath to above the chassis.   Exactly the same split-floor arrangement appeared in a one-valve short-wave set featured in the 1957 edition of Fun with Radio (the design was dropped from later editions when Fun with Short Waves was published; several designs in this book feature the split chassis arrangement). Was my recollection also right about the component positions, though?   Had Gilbert Davey 'flipped' the layout over specially for the TV series for some reason?   I did have one strong clue.   (You need a clear head for this bit!).

Reconstructed rear views of my     original set as modified, with LF     transformer mounting shown.

When I added a second valve to my original Studio ‘E’ set (see MY ORIGINAL STUDIO ‘E’ SET page), the inter-valve coupling was via a bulky LF transformer which I mounted on a vertical length of wood fixed to one of the aluminium brackets bracing the front panel.   These same brackets have gone into my rebuild.   They are a "handed pair", and the aesthetic choice of which to use each side is obvious.   I had drilled a hole in the right-hand bracket to fix this bit of wood.   That hole is still there.   (See also the second photo on the MY REBUILT STUDIO ‘E’ SET page.) The transformer was on the right as seen from the front and would have overhung either the valve or the coil, depending which was on which side.   If it had overhung the valve, it would have projected high above the front panel, even if I had not allowed headroom for removing the valve.   I don't believe I did that.   I'm sure I chose to put it where I did because this was the space-saving position above the coil, which I therefore think was on the right as seen from the front.   I fixed the valveholder for the second valve, upside down, precariously by one screw to the same bit of wood.   So I think my set (with the second valve and associated components) looked like this pictorial view (below, left). (Please see the Postscript at the end of this page.)

Reconstructed pictorial view of my     original set as modified, with LF     transformer and second valve fixed     to wood batten (shown cut away to     reveal screw hole in bracket).

I am relying purely on memory in believing that the tuning capacitor was on the left (seen from the front) with the reaction capacitor on the right.   But if I am correct about the swapped positions of the valve and coil, it would not have been unreasonable to swap the capacitors too. My guess is that the BBC wanted their own special version of the one-valver for the series, that Gilbert Davey adopted the split-floor design from the short-wave set to ease the task facing thousands of amateur constructors, and that the practical layout was 'flipped' left-to-right simply to further distance the Studio ‘E’ version from the about-to-be published Fun with Radio version.   Whilst the chassis and layout guidelines in Fun with Radio are quite loose in some respects, it would have been important for the Studio ‘E’ series to have a tightly-defined physical design which would ensure the success of the "point-to-point" wiring instructions that several contributors to the vintage-radio.net thread remember in the leaflet. It became clear from later research that the layout was re-cast several times for different publications and for various reasons over subsequent years - see DAVEY 1-VALVER HISTORY.   Performance of a simple set like this would, I presume, have been unaffected by these variations in layout.

One of my layout planning sketches,     with colour-coded wiring runs, e.g.     HT +ve = red, earth = brown, etc.

Now committed to positions for the valve, coil and the two variable capacitors, the next step was to decide on the orientation (seen from above) of both the valveholder and the coil.   As both had to bridge the slot in the chassis, there were effectively only two orientation choices for each.   This was a matter of “joining the dots” to arrive at some practical layouts, and seeing what worked best in terms of short and direct wiring runs. The choice for orienting the valve was clear.   Orienting pins 1 and 7 (filament) towards the rear of the set shortened the earth connection to pin 1, placed the large 0.1μF bypass capacitor out of the way beside the side runner, and placed the control grid connection (pin 6) facing the coil. With the coil, there was less to choose between the two possible orientations.   As can be seen from my sketch layout, I changed my mind a couple of times.   Eventually I placed the tag-ring slot towards the rear of the set to bring pin 6 marginally closer to the valve. The choice of positions for the rear terminals (aerial, earth, phones) was easy - the aerial/earth pair next to the coil (with the earth terminal inboard), and the phones terminals next to the valve. I have not produced finished wiring diagrams; the photos on the MY REBUILT STUDIO ‘E’ SET page serve this purpose.   They also serve better to illustrate some of the detailed layout decisions I took (both during planning and building), and these details are explained on that page.

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Postscript June 2011:   This somewhat laboured account (congratulations if you've stuck with it) has been made quite irrelevant now that a copy of the leaflet has turned up - see THE STUDIO ‘E’ LEAFLET page. We can now see that I placed the LF transformer where I did, not because the coil was that side, but because there was nothing that side!   The original valve was dead-centre on the slot, and the coil was on the far side - on the left as seen from the front of the set.   I think I placed the grid-bias battery for the second valve underneath the transformer. For my conjectural rebuild, having convinced myself that the coil was to the right of the valve (as seen from the front), I went ahead and devised the optimum wiring layout for that arrangement, with the valve's filament connections towards the back of the set, and the grid capacitor's connections on valve and coil facing each other.   In contrast, the leaflet's (under-chassis) layout shows the two unused pins of the valveholder facing the coil.   The grid capacitor C3 therefore has to be "wrapped" around the valve to find its connection points. My musings did enable me to build a set which satisfied me at the time and has stimulated others.   Pending a reconstruction according to the leaflet, I will leave this page and the MY REBUILT STUDIO ‘E’ SET page in place on the site.   However, if Gilbert Davey's shade will forgive me, I confess that I will have mixed feelings about altering my set!