One of My Favorite Receivers - the BC-348-Q
If you're one of those who absolutely cannot stand to see ANY modifications to a piece of surplus equipment, then please, read no further.
I use my radio gear, and make whatever modifications are necessary to get the job done!
Several years ago, I was fortunate enough to obtain a BC-348-Q receiver (which was in very good condition) from a local area Ham who was retiring and moving out of town. I felt quite fortunate, because I consider the BC-348 series of receivers to be some of the finest radio gear to come out of the WW-II era.
I wanted to be able to use this receiver for general purpose listening and enjoyment. Since I did not plan to operate the radio on 28 volts as was originally designed, I decided to convert it to AC operation. As it turned out, this was necessary anyway, since the internal Dynamotor was inoperative.
This is the way the receiver looked when I brought it home. I suspected that the radio had been modified internally, because when I received the radio, it came with an external power supply which was mounted inside a separate case along with a loudspeaker. The receiver itself was in fairly good condition for having been in storage for so many years. The previous owner had stored it in a bedroom closet, so the receiver was fairly well protected from the ravages of time and insect infestation. The front panel was somewhat faded, and the paint had quite a bit of dust adhering to it. Other than that, it looked pretty nice. But, what about the inside of the receiver?
Wow! This beauty looks like it just came from the factory! Everything looks clean, neat, and in place. All the lettering is clear and easy to read. The only thing that was wrong was that the Dynamotor was inoperative. Someone had removed the brushes and brush holder end caps and disconnected all the wiring from the base plate that supports the dynamotor in the receiver. I did not consider this to be a serious problem, since I had planned to convert the radio to operate from the AC mains.
Yes, the interior of the receiver was really this clean and shiny when I opened the case! Even the original JAN tubes were installed in the sockets. Inside, the radio looked factory-new. You can see that I have removed the inoperative Dynamotor and remounted the base plate in the receiver. I'll use the mounting plate to hold an internal AC power supply. Most AC power conversions for this radio will place the power supply outside of the receiver, but, with care, it is possible to fit a power supply inside the radio. Using solid-state diodes instead of a vacuum tube rectifier reduces the heat considerably and allows mounting the AC power supply inside the radio.
Here's the AC power supply installed in the receiver. The two transformers fit nicely in the space formerly occupied by the Dynamotor. The left transformer came from Radio Shack and supplies 24 volts for the filaments. The right transformer supplies plate voltage. It was salvaged from some unknown piece of test equipment many years ago.
Sharp-eyed surplus buffs will quickly spot a couple of new wires and a rewired power connector in this view of the bottom of the receivers' chassis. The new high voltage rectifier diodes and wiring for the new AC power transformers are hidden under the two-section oil-filled capacitor visible in the lower left of this photo. Other than these useful changes, the receiver is unmodified.
An oblique view of the receiver after the AC power supply modification and some careful front panel cleaning.
Here is the end result of my semi-restoration efforts.
A gentle cleaning of the exterior of the cabinet and the front panel reveals the original lustre and beauty of the BC-348-Q. And yes, all the controls do work as intended. I added a small Radio Shack loudspeaker to the setup. The finish of the speaker cabinet and the design of the grille makes it look almost as though the speaker was designed to go with the receiver.
73, Ralph W5JGV
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