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Airzone 1945 / 1946 MW / SW
I believe the model to be a 6552A schematic from the AORSM(1947)
Airzone 1945/1946 Bakelite radio was brought to me as a customer repair. Being owned by his mother the customer wanted it electrically restored to past it down to his daughter. On inspection of this 72 year old set there was quite a few faults, first being that the lead wires insulation coming from the transformer were so badly deteriorated that the wires would have caused a dead short. So I removed the transformer and untangled the lead wires and did some testing. Once tested I had found that one side of the H.T coil was burnt out. I tested the Valves and found two to be completely dead even though the heaters were working. I carried on testing the other components of the set then once I had made sure power was safe to connect I pulled out my trusty H.T portable test power supply with 6.3v and temporarily connected it to the set. I fitted two other valves and turned on the PSU and the set fired up and was receiving all the AM stations and then went dead except for the fluttering sound of the voice coil, yep, it split in half. So least the set was going and all the other faults can be repaired, so after getting the go ahead from the owner I rewound the H.T windings, I was very lucky as the 6.3v and 5v windings just slipped off the H.T windings, and after rewinding the H.T's the 5v & 6.3v windings slipped back on again, with a bit more of a push, I cleaned all the lamination down and resprayed them with an electrical insulation spray to one side only and I was able to get every lamaination back in and once together, I bench tested the transformer to be working fine. After writting the above on the transformer after bench testing it ok, I fitted it back into the set I re-tested it and nothing. The tap from 230v to 250v had 5 ohms but nothing to the common on the primaries. After all that work I had to strip it down again and take off the primaries and rewind the lot. LESSON LEARNT, rewind from scratch ! On to the speaker voice coil, after removing the speaker cone and gasket there was just a coil of wire that was all in a mess, so after fiding the resistance of the voice coil I rewound a new one. I ordered some speaker parts from the USA to complete the speaker repair with a new spider and cone and resheathed the coil wiring. The Valve layout is: 6A8G 6U7G 6B6G 6F6G 5Y3G.
Before the complete rewind
After Primary and H.T. windings
Full Transformer Rewind