My Rebuilt Studio ‘E’ Set On this page, for the time being, the pictures and text relating to my conjectural Studio ‘E’ rebuild remain as they were, so that you can compare it with the leaflet.   For all my careful reasoning, you can see that I was some way out!   In due course, I hope to re-build my set to accord with the leaflet.   I will then recast this page with new pictures and text.

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My conjectural rebuild of the Studio ‘E’ set. Practical Details

The completed chassis.

The panels on my chassis are of 3mm Tufnol - the closest to Paxolin you can buy nowadays as far as I know - if you have a secret supply of pukka Paxolin, do tell!   Each panel was cut approximately 2mm oversize, then brought to exact size and squareness with a sharp block plane to avoid chipped edges.   The front panel is 5 1/2” wide x 4 1/4” high.   The mounting holes for the variable capacitors are 1 1/2" from top and side edges.   The two chassis floor sections are each 5 1/2” x 2 3/8”, spaced apart to suit the valveholder. The runners are beech, 1” x 9/16”, planed and sanded, treated with one coat of clear polyurethane varnish, flatted off with "wet and dry" paper used dry, then wax polished. These dimensions are all guesses at those originally specified.   The chassis is assembled with brass wood screws (3/4" x no.6 c/sk), and brass bolts (6BA x 1/4" c/sk) and nuts. The chassis incorporates the aluminium brackets from my original set.   Clearly visible (arrowed) is the hole drilled in the further bracket when a second valve and associated components were added to the original set.

Home-made wander socket strip.

I couldn’t find wander sockets to buy in paired strips as I remember from the original, so these were home-made from 1/16" paxolin (back of an old consumer unit), with receptacles of thin-gauge sheet brass rolled round a drill.   These were each peened over at one end to form a flange, flattened at the other end to form a solder tag, and this tag drilled with two small (1mm diameter) holes.   They were positioned in the paxolin strips, then secured with rings of copper wire (from house-wiring cable) soldered in position. I made "vintage-look" sleeving by stripping the centre threads out of nylon light-switch pull cord and painting the remaining braided sleeve with knotting varnish.

Top view.

Here are two large-scale views of my set.   In the top view, note that: 1: Connections to the variable capacitors are F = fixed vanes; M = moving vanes. 2: The coil connections are numbered clockwise starting at the tag-ring slot (see also circuit diagram below).   They are: 1 & 2: aerial winding; 4 & 6: grid winding; 3 & 5: reaction winding. The tag-ring slot faces towards the rear of the set.   Note also the link between pins 2 and 4. (While cleaning up the coil's tags for re-use, I learned the hard way how fragile its construction is.   I applied a little too much force; suddenly the tag-ring parted from the former, and three of the delicate coil connections were broken.   The air was blue!   I had to do some very intricate soldering to restore order.) 3: The valve has been removed to show that pins 1 and 7 of the valveholder face towards the rear of the set; 4: The destinations of through-chassis wires are given.

Bottom view.

In the bottom view, note that: 1: The valveholder connections, reading clockwise (for DAF91 or DAF96), are: 1: filament –ve (and internal connection to suppressor grid); 2: not used; 3: not used; 4: screen grid; 5: anode; 6: control grid; 7: filament +ve. 2: For the resistors and capacitors, I used “vintage-look” modern components (Geoff Davies Radio).   The large 0.1μF capacitor (C4) came with a garish glossy yellow cover, so I took this off and substituted a "vintage-look" sleeve of manilla paper. 3: C3 (grid capacitor – flat red component) is just visible behind R1 and R2, above the chassis floor.   Its value is 180pF, a modern near equivalent to the .0002μF originally specified. 4: The leads of R2 and R3 were extended (black sleeving) – see fuller note below. 5: The destinations of through-chassis wires are given.

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.

For ease of reference, here is the circuit diagram and components list (see PLANNING MY STUDIO ‘E’ REBUILD page) upon which my rebuild is based. I think I am right in saying that strictly the circuit as shown was slightly incorrect, in that the suppressor grid (nearest the anode) was shown connected to the LT+ve end of the filament.   However, the practical layouts published with it in Fun with Radio correctly showed pin 1 (which carries an internal connection to the suppressor grid) connected to LT–ve.   I have followed this latter arrangement in my wire-up. There are six general points to note about the wiring layout as I have done it: 1: It is my best guess at a reasonable layout given the decisions I took on placing the coil, valve and variable capacitors (see PLANNING MY REBUILD page).   Memory has not guided me for the wiring layout itself except for point 5 below. 2: I have included the switch in the LT+ve supply that my father fitted to my original set, but which was not specified in the Studio ‘E’ design, which I presume would have shown LT+ve wired direct to valve pin 7.   Cutting off the LT supply does indeed cut the HT off since, with the valve not conducting, there is no DC path from HT+ve to ground. 3: The connections to the valveholder are as for DAF91 or DAF96.   The connections to alternative valves which feature in other published versions of the circuit, such as DF91, DF96, 1T4, are different. 4: I have improved on the original arrangement for the battery connections, which I believe was separate unsupported wires to the 4-pin battery plug, vulnerable to breaks.   I used two lengths of twinflex (red and black cores) passed through a rubber sleeve which is secured by a saddle held by the inner two fixing bolts for the paired wander sockets.   Not then having any information about the socket connections on the original HT/LT batteries, I made my own decisions when wiring up my original 4-pin battery plug and new power pack, but purely by chance I seem to have guessed right - see battery pack picture below.   I also added a metal sheath to the plug. 5: You will see that the sleeving on the connection to tag 6 of the coil (top view) is split, and the 180pF grid capacitor, C3, is connected here rather than to the tag itself.   I have a definite memory of a connection like this on the original set (visible from the top), and I also remember that at least one of the "point-to point" instructions specified a connection to the "last wire" (i.e. the connection made under the previous instruction).   This makes good sense in this particular location because: a) the small-value grid capacitor (even a period component) might not have had long enough leads for the distance between valveholder (pin 6) and coil (tag 6) especially if the builder had placed them far apart on the chassis slot.   Connection to the wire at an intermediate point solves this problem. b) an amateur solderer might have trouble securing, in successive steps, both a wire and a component end to a tag on the coil with no hole, without risking overheating the tag and disturbing the delicate connection to the winding itself. I have therefore reproduced my memory in what seems to me to be the most appropriate place. 6: I found that I had to extend the leads on two of the resistors (R2, 10k and R3, 470k), using larger (black) sleeving to go over the soldered joint.   My chassis is possibly deeper front-to-back than the original, and the modern resistors (although "vintage-look") have quite short leads.   I might just have managed by taking a direct line with each of these, but I opted to extend the leads and ensure a neat layout that would photograph clearly and that seemed satisfactory from most other points of view. Postscript June 2011:   With the leaflet to hand, it can be seen that my memory of the grid capacitor wiring was not far off the mark.   With the valve and coil arranged as per the leaflet, connecting the grid capacitor C3 to an intermediate point on the wire to the coil was even more essential in order to avoid wrapping C3 and its connections right round the valve! The chassis of my conjectural build is indeed 3/4 inch deeper than the leaflet specifies. Even so, according to the drawing, one lead of R2 (anode resistor) would likely have to be extended. Performance and Listening Powered by my rechargeable battery pack (see below), my set operates well on about 14 metres of aerial in the loft.   Reaction works well over virtually the whole medium-wave band.   Spanish, Polish and Russian stations have been heard. The medium-wave band is now something of a desert, as its use for a.m. broadcast declines.   The hallowed 208 metre (1440 kHz) spot on the dial once occupied by Radio Luxembourg is now taken by China Radio.   A mild dose of nostalgia can be had on Gold (music from the 60s, 70s and 80s) from about 38 local transmitters at various spots on the band. Power Pack

My home-made battery pack,     ready for use.

I started work on the power pack first, while I was doing research on Gilbert Davey's work and making early efforts to locate the BBC leaflet.   As the old HT or combined HT/LT batteries are now unobtainable, I weighed the merits of building either a mains-driven power supply, or a power pack using rechargeable batteries. I decided quite quickly to build a pack using NiMH rechargeable batteries.   My unit has ten PP9 rechargeables in series (8.4 volts each), and four AA rechargeable in parallel, housed in a case made of beech and 3mm Tufnol. As mentioned above, I made my own decision on how to wire the power plug and socket (see picture).   As it happens, I got all four right.   See www.the-thompson-brown-family.co.uk/batteries/batteriesframe.htm (in the left-hand navigation, under "Batteries", see "Some battery info" - the centre image shows B114 socket connections, size, voltages.   Under "Valve", there are battery case scans - these are copyright, for non-profit use only.)

The battery pack with     the lid removed.

The lid, secured with four brass "side hooks", carries the following: * a home-made socket with contacts of phosphor bronze (fiddly to make!) to receive the original 4-pin battery plug; * gold-plated steel twin conical springs for the series HT links (I just happened to have these!), carried on a paxolin plate.   Up to 84v is available in 8.4v steps by re-positioning the HT+ve connection – photo shows this positioned for 67.2 volts.   I could instead have simply poppered the PP9s together with their male and female connectors, but I had the springs to hand and thought that their use would make it easier to remove the batteries for recharging and make a more elegant package. * parallel LT-ve connections - four nickel-plated steel conical springs soldered to a square brass plate. The LT+ve connection in the base of the pack is a square brass plate (same size as that seen on the lid) with four upward-facing pips (centrepunched), from which a wire goes to the 4-pin socket via a spade connector.   Splitting this allows the lid to be removed entirely. Two Tufnol bulkheads form a small compartment between the two battery banks.   This houses the tails of the 4-pin connector and the surplus wires leading to them, which are tidied with a short length of plastic sleeving. The battery pack is entirely reliable, with no evidence of crackling, and several hours of listening have been undertaken without the need for recharging. Having made this battery pack successfully, I discovered afterwards that mains-powered battery eliminators are available complete or as kits, providing 90v HT and 1.4v LT, and also that designs for self-build are available for download.   I doubt therefore whether other builders will wish to make a battery pack like mine, so have not given details as full as for the receiver itself.

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For details of these mains-powered packs, and for a breakdown of the materials and components I used in my one-valver, with possible alternatives for other rebuilds (including a home-made coil in place of my commercially-made one), see YOUR STUDIO ‘E’ REBUILD . . . page.