The 51J-4 had been sitting for many years or even decades. In January 2023, the filter capacitor was bad and was replaced, but the receiver barely functioned and sounded very bad. Fast forward to May 7, 2023: I brought it to the bench and cleaned all the rotary switches after which, it sprang to life. The BFO circuit has issues that need to be resolved; it is currently unable to tune single sideband signals. Otherwise, the 51J-4 works remarkably well given the time off line.