Your Studio ‘E’ Rebuild . . . With the Studio ‘E’ leaflet now to hand, some of the details on this page are superseded, and will be corrected fully when I have reconstructed my set.   I am fortunate in having kept many of the components that went into my original set.   Of these, the Teletron coil would undoubtedly be the hardest to find, so this page begins with details of the home-made coil which I tried out in my conjectural rebuild.   This is followed by details of the original and new components in that set, suppliers for the new components, and suggested alternatives for other rebuilds.

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Please note: It is your own responsibility to ensure that you work safely and that equipment (especially any mains-operated power supplies) is soundly built and adequately housed.   If you are in any doubt about your understanding of the information given or referred to on this page or about your ability to work safely, you should seek the help of a qualified person. Before fitting the valve, follow Gilbert Davey's advice and check that HT voltage is not reaching the filament connections. Connect a torch bulb (traditional - not LED) across them.   With HT and LT supplies (and phones) connected, the bulb should light dimly.   If it blows, something is wrong and the fault must be found and corrected before fitting the valve. Home-made coil Having got the set working with the Teletron coil, I made an experimental home-made coil.   This was inspired by a Davey design for one of the other one-valver versions published over the years, but took account, using other published data, of the wire I had to hand.   It was then altered as described below, in the light of trials on my set.   I decided to make a medium-wave-only coil, to match the function of the Teletron coil.   This would limit its physical height so that it would not project above the front panel, and I didn't want to add a wavechange switch.     My experimental coil as first made. For the coil former, I used a 2-inch diameter cardboard tube from kitchen roll.   Toilet roll is the same diameter, but kitchen roll tube is longer so there's more to hold on to.   I cut the surplus off when I had finished winding.   There are three windings (to replicate the Teletron coil) all of 26swg enamelled copper wire.   All windings are close-wound, and all in the same direction – on my coil they form "right-hand threads", spiralling clockwise and away from the viewer looking from above.   I included tappings as below for experiment, formed by twisting a small loop in the wire at the completion of a turn, and then continuing winding.   These loops were scraped clean of enamel when the coil was finished. To guard against kinking during winding, I placed the supply reel on a screwdriver held vertically in the vice so that it could turn freely.   At the beginning of each winding, I punched a pair of small holes through the tube about 1/4” apart, threaded about 9” of wire through (in through one hole, out the other) for connection, and wound on turns as below.   When each winding was complete, I cut the wire to leave another 9” for connection, punched two more holes, and threaded the wire in and out.   The gaps between windings are about 1/4”.   The windings are: Reaction (top), 30 turns initially.   After trials I added a further 8 turns at the top, leaving the original start as a tapping at the 8th turn of a 38-turn winding. Tuning (centre), 65 turns, with tappings at the 55th and 60th turns; Aerial (bottom), 20 turns, with tappings at the 10th and 15th turns. The drawing sums up these details.

Drawing giving details of     my experimental coil.

The numbers in quotes correspond to the pin numbering on the Teletron coil.   The destination of each connection is given.   Note that connections 2 and 4 are stripped of enamel for a short distance (say 3/8”) where they leave the former, and are then twisted together and soldered.   This leaves the aerial and tuning windings joined together, with two long leads from the junction. To mount the coil to the chassis, I made a hardwood block, about 1 3/8” wide and 1/2” thick, with curved ends for a push-fit inside the former.   I drilled fixing holes to use with those already drilled in the chassis for the Teletron coil.   Why does my block have four holes (first photo on this page)?   Because I initially drilled the fixing holes on the block’s centreline, but found that with these holes lined up with those already drilled in my chassis, the large home-made coil covered most of the useful gap in the centre of the chassis.   So I drilled two more offset holes to shift the coil towards the side.   If you are making this, you can drill just two holes on the centreline of the block first, try it on the chassis for position, then drill the chassis to suit. With this block bolted to the chassis, the coil slips over it.   Take care that the block does not foul the end of the aerial winding where the wire is inside the former. Note: If you follow the leaflet's layout, the coil will go on the left of the set as seen from the front - i.e. the reverse arrangement to that seen in the picture below.   The leaflet shows the valve mounted centrally in the slot.   In order to place this large home-made coil in the correct place, it will be necessary to shift the valve somewhat to the right as seen from the front of the set.

My experimental coil installed     after altering the reaction winding.

After trials, I found that the full complement of turns on both the aerial and tuning windings worked best, so the tappings on these were redundant.   With the reaction winding as first made, I found that reaction was rather less lively than with the Teletron coil, so I wound on the 8 extra turns as stated.   Using all 38 turns, performance seemed to be about the same as with the Teletron coil, although I could not of course make instantaneous comparisons.   The tapping so formed was therefore also redundant. If you are using the same gauge of wire and don’t want to experiment, you can just make the coil with the full number of turns (38, 65, 20), without the tappings.   If you use a different gauge of wire, you may need to experiment with the number of turns for each winding.   You may also want to consider painting the completed coil with clear polyurethane varnish, to strengthen the former and fix the windings in place.   I did not bother to do this as I have re-fitted the Teletron coil to my set. Table of components and materials Revised (June 2011) in the light of the Studio ‘E’ leaflet.   Note that Column 2 still relates to my conjectural set, which has not as yet been altered to accord with the leaflet.

My original set		My conjectural rebuild		Supplier for my rebuild	Alternatives for other rebuilds
				(* = contact details earlier in table)	(* = contact details earlier in table)
Chassis panels: 1/8" Paxolin sheet		Tufnol sheet 3mm		www.directplasticsonline.co.uk	3mm plywood
Chassis runners:		Beech		DIY store	Any other hardwood
Chassis brackets: aluminium, marked "PRANCO" (not in published design)		Originals		-	Fabricate from 16swg aluminium or omit.   If omitted, ensure firm screw fixing of front panel to runners.
Wood screws:		Brass, 3/4" x No 6, slotted countersunk		DIY store	Steel screws
6BA screws, nuts, washers:		Front panel to brackets: Brass, 1/4" slotted c/sunk.    Brass nuts. Elsewhere: Nickel-plated brass, 3/8" slotted round head; nickel plated brass nuts, washers.		ebay seller ebay seller Geoff Davies Radio, 01788 574774	M3 equivalents M3 equivalents M3 equivalents
Knobs (2):		Originals		-	Vintage appearance pointer style, Geoff Davies Radio *
Terminals: paired wander sockets on Paxolin strips		Fabricated from 1/16" Paxolin and sheet brass - see text		-	Modern single equivalents, Maplin www.maplin.co.uk
Wander plugs: 2 red, 2 black		From spares box, may be originals.		-	Modern equivalents, Maplin *
Battery plug: 4-pin, to suit original (B114) HT/LT battery		Original - metal sheathed for rebuild		-	Any small 4-pin plug, and matching socket for power supply. See Battery (below).
LT switch: make unknown (not in published design)		Original		-	Any suitable SPST switch, e.g. Table Light Switch (push-button) FH94C, Maplin *. If omitted - LT+ve goes direct to valve, pin 7. Unplug after use if using batteries.
Coil: Teletron D/R, with aerial, grid and reaction windings		Original		-	Home-made coil, see above. Enamelled copper wire 26swg: Cricklewood Electronics www.cricklewoodelectronics.com
Valveholder B7G:		Original		-	Geoff Davies Radio *
Valve, DAF96:		Original DAF96 and DAF91 used.		-	Geoff Davies Radio *
Variable capacitors: C1: .0005μF/500pF; C2: .0001μF/100pF solid dielectric		Originals		-	Getting hard to find - try ebay or www.6v6.co.uk
Fixed capacitors: C3 (grid): .0002μF C4 (bypass): 0.1μF		180pF (modern value), reasonable "vintage" look Modern 0.1μF 1000v, "vintage look" sleeve made		Geoff Davies Radio *	Geoff Davies Radio *
Resistors: R1: 2.0MΩ R2: 5kΩ R3: 220kΩ		2.2MΩ, "vintage look" 10kΩ, ditto 470kΩ, ditto Values as Fun with Radio, 1957.		Geoff Davies Radio *	Geoff Davies Radio *
Headphones:		High impedance, 4,000Ω		ebay seller	ebay seller
Connecting wire:		Tinned copper, 22swg, from old stranded cable		-	15 amp fuse wire, or equipment wire, Maplin *
Sleeving: Systoflex type		Vintage look - nylon pull- cord, stripped of central strands, then varnished		-	2mm bore black vintage-look sleeving Geoff Davies Radio *
Battery leads:		Twin-core flex (2 runs), white PVC sheath, red/black cores, from old appliance		-	Modern equivalent (brown/blue cores) DIY store
Battery: Ever Ready "Batrymax" (B114)		Home-built battery pack, with AA and PP3 rechargeables - see text		Batteries- DIY store Beech - DIY store Side hooks - DIY store Tufnol - Direct Plastics Online * All other materials were to hand.	Mains-powered eliminator (to purchase), 90v and 1.4v, cased or uncased 6v6.co.uk * Mains-powered eliminator (self-build), www.vintage-radio.com

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Suppliers do change their lines, so please check with them before ordering.   I would be delighted to hear about your rebuild of the Studio ‘E’ one-valver!