Wednesday, Dec. 29, 2010, 12:56 a.m. — With Christmas done, it is time to return to projects that were waiting in the wings … recapping my Detrola 571X AM BC receiver.
This receiver is circa 1945, and is missing the electrical cord; actually it was there, but had been spliced years ago at the stress relief at the rear of the chassis. The electrical tape was old and brittle, and I decided long ago to remove that cord before someone plugged it in and shocked themselves.
I have new caps waiting, as well as a new line cord to install. Tonight I decided it was time to get started!
There are three screws that hold the chassis in place in the bakelite housing. A sidenote from my childhood — the chassis of the radio isn’t always at ground potential, depending on which way you had the non-polarized plug inserted in the wall. When the plug was inserted “wrong” you could get a nice little shock from touching the chassis screws in the bottom of the receiver. Ouch!
In addition to the chassis screws, the knobs have to come off the shaft; on a 65-year-old radio, that’s not always an easy task. In fact, I though for sure I was going to bust the case, the tuning knob, or both before I got it loose. Trying to pry, applying pressure evenly, on a knob without marring the case is easier said than done. In the end, I used my usual high-tech arsenal of tools — a rusty steak knife, a “found” pair of needle nose pliers and a bent butter knife. What the heck, it worked — got the knob off the shaft without destroying anything.
I’m first going to tackle replacing the dual section filter cap, though this might be tougher than I thought. The schematic looks a lot different than the chassis wiring on these thing, so I have to figure out where everything needs to go … in order to avoid blowing up the works in the process of making it play better.
The receiver uses loctal tube sockets, which makes it a little unique. I believe it was Philco or Zenith that came up with the loctal socket concept for rugged applications. For years my father had his first car radio in our basement, and it had loctal tubes, circa 1940.
I’m going to assume the tubes are good for now; my tube tester is hiding somewhere, probably in the attic.
So the first job will be to replace the caps and the line cord … then I’ll see where it stands. The schematic has a full set of voltage checks, so I should be able to determine if at least the voltages are in tolerance.
That’s all this trip … wish me luck tomorrow when I tear into some caps. 73 de KY4Z … dit dit ….