David Macnaughton and his Fascinating World of Amateur Radio

BC348M RECEIVER RESTORATION PROJECT

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My BC348M Receiver A project to upset the purists!     Click image to view full size    This project will upset the restoration purists. The old BC348M was given to me but someone in the distant past had got to it and performed a major series of modifications - as hams used to do. The result was a mess of very untidy wiring that could not have possibly worked. My approach to restoring it was to rewire it to almost the original circuit, but since I was unable to borrow on original BC348M to copy from, I rewired it almost to the original circuit, but the small components have been placed where I could fit them in. The exception to the original circuit has been the AC power supply that I fitted in place of the dynamotor and audio output stage that now has a TV tube 18GV8. Now let me say in defense of my restoration approach that  if suitable information is obtained in the future then further work can be done to restore the unit closer to an original BC348. In the mean time it is working very close in performance to an original unit and is once again working on air. What would a purist have liked me to do? Leave it as a heap of junk, put it in land-fill, or make it work as best as I am able. Incidentally, I have always believed that when restoring any old equipment, unless it is to be used as a static display in a museum, it must be made to operate.  After all, when it was new it did operate, so how can equipment  be claimed to be restored to original condition unless it does operate? I have no room in my little shack for static displays.   The output transformer (top centre) was open circuit so had to be replaced. The power supply (top left) supplies +250V for the HT and 19V for the heaters.   The small components have been fitted where I felt they should go. The unwired tube (bottom left) is a 12BE6. It was to be a product detector but I consider the performance of the original circuit good enough on SSB so the tube will be removed. Note the mains input socket (bottom centre). I considered that if the unit was to be connected to the 240V mains, then the socket had to be at least to a professional standard for safety. It is a mains filter and socket from a computer. The 18GV8 audio tube can be seen just right of centre. The power supply is bottom right. Otherwise it is a BC348M