There is a 10Mfd. bathtub capacitor in the audio driver B+ circuit. This has failed open, is this the usual failure mode of a bathtub capacitor? The variable oscillator is VERY touchy to align. Short term stability is OK, but each time the box is turned on, the calibration is off a kc or so. (I removed the reactance tube and disconnected the coupling cap to the reactance circuit.) Any ideas? Jim