R1155 Ser. 40696

14 minute read

November 2011

Restoring another R1155

The following pages detail the strip-down and rebuild of another R1155 ... In this case an ‘A’ variant with the later, ‘type 35’ tuning mechanism and belongs to a friend of mine. The acquisition and refurbishment of this set actually serves to highlight the difficulty in getting a complete R1155. I was initially presented with no less than three derelict 1155s and asked if I could make a complete one out of the three. The short answer was no! This one was eventually bought at a rally and on the face of it, looked largely intact. However, my friend had been unable to view the internals at time of purchace. The photograph on the left is a little misleading since it did come with a tuning indicator. When I took this photograph, just prior to stripping it down, I had already taken all the valves out for safe keeping. What was immediately obvious was the lack of labels for ‘Meter Balance, the long triple label in the top right corner and those associated with the meter deflection switch, which itself was missing. I may be wrong, but I suspect the volume control knob is wrong too. The ‘Pencil Strip’ was missing, as were the two supports for the metal strap that retains the Jones connectors. Everything else on the front panel appeared to be in order. However, looks can be deceiving!
As expected, ALL the DF circuitry was missing ... That is V1, V2, V9, the entire contents of the rear compartment in the BFO/DF unit, the 2 wave-wound inductors that comprise L24, the transformer known as L23, the DF tag-bard on one end of the coil-box, the three capacitors that are normally next to the bevel gears and associated with V9 and 3 of the iconic tall tubular metal-can capacitors. As previously mentioned S2 was also missing. Not only was the DF compartment empty, but it also had a huge hole punched in it. The Meter Balance and Meter Amplitude potentiometers turned out to be ‘space fillers’ and the unique dual-gang AF/RF gain potentiometer had been replaced with a single-gang potentiometer. I was going to have to do a lot of hunting for replacement parts before I started!

The lid for the coil-box was also missing as was the Aural Sense tag board. Whereas 2 of the front-panel controls had just been fitted to fill holes, the replacement of the dual-gang AF/RF gain control did appear genuine. Traces of modern PVC covered wiring (bright green) gave the impression that at some time in its history, this particular R1155 had been modified. On the ‘bright side’, I found one wave-wound inductor lying inside the DF compartment along with a variety of other DF circuit components. Fortunately, before my friend eventually disposed of his three derelicts, I had the presence of mind to salvage a number of parts. These included, a complete BFO/DF compartment, a pencil strip, a complete coil-box complete with lid, the bunch of capacitors associated with V9 that are mounted on the coil-box adjacent to the bevel gears, and several front panel labels! The last remaining wave-wound L24 inductor was provided by Roger Scott, G4KVQ by way of a request for parts on this website. Peter Holtham, VK4COZ very kindly provided the nearly impossible to find L23 transformer. The latter was known to be faulty but turned out to be what I think was a manufacturing error ... The outer end of the outer winding was not actually soldered to the wire leading to the tag on the top! Easily fixed!! The DF tag-board (stripped), Meter Balance pot, S2 and the Aural Sense tag-board assembly were all obtained over time via eBay and another 1155 enthusiast, Phil Staplehurst, came up with the Meter Amplitude and AF/RF gain potentiometers as well as the three missing tubular capacitors. Over all it took the best part of 18 months to collect all the missing parts. I was now ready to proceed!

The photograph on the right shows the bare chassis. Having previously stripped my own AD8882B, I already had the bags in which to store the individual components/assemblies for future use. As I took it apart, I was aware of a distinct petroleum smell. As you can see from the photograph there is a residue of something clinging to the chassis. I do wonder if this was the result of an airborne incident or whether someone had used petrol to clean the set. If it was the latter, it was not effective.

The photograph on the left shows the terrifying coil-box stripped, cleaned and awaiting re-assembly. The original wiring was in an atrocious state with the insulation instantly turning to a gooey mess when the soldering iron was applied to the wire.

This is the closest you get to a printed circuit board in the R1155. This is the Bias tag-board which is tucked away under the chassis, under the main system switch. Note where I have joined either two or three resistors in series. It is vital not to use nearest preferred value resistors since this board determines the bias voltages used throughout the receiver. 30K is achieved by three 10K resistors in series and 200R is achieved by two 100R in series.

The chassis cleaned up rather nicely. The photograph on the left shows some of the controls and assemblies aleady rebuilt and installed. The Aural Sense tag-board is the little board with four (but occasionally six) resistors, mounted on top of the Aural Sense switch, top left in this photograph. All the rubber grommets have been replaced and the valve sockets carefully cleaned and refitted.

Another shot of the chassis, this time the underside. I suppose it is actually interesting that in a way, the chassis tray is upside down. When the set is upright, the horizontal part of the chassis is like a tray with a raised edge all the way round. I don’t think there is any  special reason for this other than bending the chassis in such a way increased the rigidity of the structure. The R1155 was designed to be cheap and light.

I have put these two photographs together because they serve to demonstrate the methodical, systematic rebuilding process as explained in Peter Holtham’s book. It is both interesting and poignant that the R1155 was never designed to be disassembled once assembled. Since the life of a bomber during the peak of Bomber Command’s campaign in WW2 was measured in weeks, typically three! As a result, the front panel was welded to the chassis and could not be removed. As a result the order of reassembly has to be chosen very carefully and occasionally appears haphazard. For instance, the 9-way tag board, top left in both photographs needs to be wired early on since once the coil-box is installed, access to the board becomes greatly impaired. Also note that in the bottom photograph, the three capacitors associated with V9 have already been wired, although they are eventually attached to the end of the coil-box. Anyone who has attempted to fit these after the coil-box will know how frustratingly difficult that can be. These two photographs also show how satisfying the reassembly can be ... Giving you an opportunity to ensure that the wiring is neat and tidy.

If the thought of rewiring a coil-box doesn’t frighten you, the wiring around the System Switch might. What I did this time was to re-wire the inter-switch connections at time of disassembly. This made the final wiring of the switch much easier. However it did also raise some confusion. See the photograph on the left. Note the yellow wire from the earth solder-tag on the rear mounting plate that goes to the switch at about ‘8 o’clock’. This wire isn’t in Peter Holtham’s book. In the book, that switch connection goes to the 4-pin Jones socked and is earthed to the chassis at the connector. In actual fact, in this particular receiver, the wire between the connector and the switch was earthed to chassis at both ends. I eventually removed the wire earthing the switch to the chassis since it was a duplication. But this goes to show that maintaining consistency of manufacture over 6 different factories did have its difficulties.

And then ... Just to prove a point ... Two views of the wiring associated with the System Switch. Sometimes it is necessary to remove the Hum Filter assembly for access to the AF/RF gain control. At this point, access is still required to the awkwardly mounted 9-way tag-board as wires are still being routed to it. With all the wiring to the System Switch complete, you are left with a bunch of wires, above and below the chassis with labels attached ... Or at least you should have!

Having spent at least a day rewiring the coil-box, we can now re-fit it to the chassis.This is relatively easy provided you have left long enough wires for connection between the coil-box and the chassis and vice-versa. Again, the order in which to do the wiring is carefully thought out and detailed in Peter’s book.

The end result is both impressive and satisfying! I actually use artery forceps for gripping wires in awkward places.
The photograph above shows the area around the bevel gears, including the three capacitors associated with V9, now mounted on the coil-box end. This photograph shows the area around the opposite end of the coil-box. In many R1155s, this area has been completely striped out since everything here is associated with the DF circuit. A photograph of the finished R1155A, re-aligned and tested ... Always best to test it prior to lacing up the wiring! ...

... and a photograph of the underside with the coil-box lid in place. It worked first time!
The finished R1155A
The tuning scale has cleaned up nicely and an authentic pencil-strip has been fitted. The dubious AF/RF gain control knob has been changed for a genuine one and all the missing labels are now in place. One thing that I have noticed on this receiver is that the band-change knob is permanently slightly out by more than one tooth on the bevel gears. This implies that the hole that has been drilled through the shaft, that holds the pin for aligning the knob, is lightly out. A quaint peculiarity maybe? I still don’t have the pillars and metal strap for securing the Jones connectors, but that really isn’t an issue. Alignment and testing was largely straightforward and uneventful. The radio worked first time ... The moment it was switched on! When I stripped the coil-box and released the cores in the many inductors, I made a note of where the end of the core was in relation to the rear wall of the coil-box. Then when I refitted the core, I was able to screw it back in to (almost) the same position. The only unexpected problem that arose was that the two ceramic trimmers that adjust the high end of bands 1 and 2 had seized. These were replaced with the same two trimmers from the salvaged coil-box. Apart from that, alignment went as per the book with minimal adjustment required. The R1155 was never intended for resolving SSB. On my AD8882B, I have the BFO set for resolving LSB on 3.5MHz and 7MHz. However, on this R1155A, I found that very strong LSB signals on 7MHz were ‘impossible’ to resolve, whilst moderate SSB signals on both 7MHz and 14MHz were resolvable for the same BFO setting. This had me scratching my head to the point that I carefully measured the LO frequency to ensure that I had not tuned it to the ‘image’ (RF - IF as opposed to RF + IF). The Local Oscillator was indeed set correctly on both bands. The BFO was working fine but I was getting the impression that I was not able to bring the actual 280KHz (IF/2) signal low enough in frequency even when the tuning capacitor was fully meshed ... And when I attempted to adjust the inductor in the BFO, the top of the ferrite core came away! I compensated for this by paralleling a small Silvered Mica capacitor (39pF) across the tuning capacitor. This enabled me to bring the frequency lower but I still had problems with very strong LSB signals on 7MHz. However, you have to bear in mind that the R1155 is NOT a modern top of the line contest-winning HF receiver with narrow brick-wall IF filters. There was an HF contest on at the time and it’s at times like these that folk tend to turn the ‘wick’ right up on their PAs, so that would explain the proliferation of very strong signals. I also found that with very careful tuning, I could in fact resolve these strong stations. I also noticed that the fine control on the Type-35 tuning mechanism is actually coarser than the older Type-13 mechanism that my AD8882B has and I am accustomed to, and this was probably why I was finding it difficult to resolve the signals. There is also a small amount of back-lash on the Type 35 mechanisms, and that didn’t help either. All-in-all, I am very happy with this restoration. Another R1155 has been brought back to life complete with fully functional Direction Finding circuitry ... Next on the list ... The accompanying T1154!