Restoring an R1155 Receiver (/cont.)
Like I said right at the start of this website, I am no stranger to the R1155 type. My first one cost me 50 pence when I was a schoolboy. It had no tuning knob, but did appear to have a hole right through the chassis where V1 & V2 should be. At the time we liked to believe it was a bullet hole. But more likely it was actually made by a pick-axe! I later heard a tale recounted by an ex-RAF Corporal who told how after the war (WW2), when he was stationed at a bomber base somewhere in England, all the decomissioned radio equipment was lined up on the edge of a runway and he and others were instructed to go along the line and smash it. Perhaps my original 1155 was one of those. I got it working by comparing it to a complete specimin. To give an idea of how uninformed I was at the time. A friend and I had obtained what I now know to have been a complete ‘Gee Set’ and promptly stripped it with the optimistic idea of building an oscilloscope in the case, making use of the tube. The large tuning knob was ingeniously re-fitted to the front of my repaired 1155. The irony of this was, at the same time (1974), the Gee Set on display at the Imperial War Museum was missing the large knob. I did consider trying to sell them the one fitted to my 1155. I later obtained a second-hand and much modified Halicrafters SX-24 (octal valves replaced with B9A and B7G ones!) ... So I sold my 1155 for three times what it originally cost me! I think at some point I obtained a second 1155, and then the old chap over the road offered me a third one which had languished in his shed for many years. Sadly the shed hadn’t had a roof for many of these years so it was in a sorry state and was only used for scavenging parts. I cannot remember what happened to these radios. Some years later, I obtained the R1155 that had been the model against which I had repaired my original. I think this was actually an R1155B since it had all the extra radar filtering. Foolishly I swapped this for a precision DMM several years later. So now in 2010, I yet again I have an R1155, and this time I am keeping it!
This one was actually advertised as a rare example of an R1155 prototype. This is probably not the case, but an understandable misconception none-the-less since I have come across an un-referenced article which stated that Marconi had already started work on the type A.D. 8882B before 1939 and that development was slow. Another reason for thinking that this is a prototype may be the fact that my set is fitted with the early (and unpopular with bomber crews) Type 13 tuning reduction drive, later changed to the Type 35. Add to that, the awful state of the wiring, it is easy to conclude that this is an early example of the type.  
A clue to the receiver’s true vintage is located on the underside of the main tuning capacitor sub-chassis. This is the switch pictured on the right. Page 10 of the AD8882B manual states               ‘Owing to the increased load on the L.T. Power unit, occasioned by the dual receiver arrangement, it is customary to remove valves V.1 (X.61M), V.2 (X.61M) and V.9 (BL.63) from the communications receiver. In certain later receivers an ordinary “On/Off” switch has been fitted on the underside of the chassis inside the receiver. In the “On” position the filament circuits are normal, all valve heaters being connected to the 6.3 volt supply. When such a receiver is fitted for communication use in a two receiver installation this switch should be placed in the “Off” position. It is then not necessary to remove any valves.’  
This is further reinforced by Peter Holtham’s excellent book ‘Restoring the Marconi R1155 Receiver’ where he includes a referenced excerpt from Sir Christopher Cockerell’s obituary which states that design started in October 1939 and took only 11 weeks from conception to installation. Finally, Peter was good enough to send me a pdf of an article published in Flight magazine from April 1947 showing two receivers described as AD8882Bs installed in a Short Solent Flying Boat. It is therefore likely that although A.D. 8882B was the initial Marconi designation of the type, no receivers actually bore that number until after 1945, and then only for a short period since manufacture ceased shortly afterwards.

Unlike the Racal RA17 series, the R1155 is not exactly modular. Even removing the BFO/DF compartment is a major exercise. So this was going to be an all or nothing restoration ... Meaning that once I started stripping it down, there would be no stopping. With the R1155, there is little opportunity to do partial testing until well into the re-build phase. I have to admit that it was very disconcerting hacking away at the wiring ... But it was well worth it in the end.