Here's the epilogue....
The K4DPK stabilizer wouldn't lock on the TR-4Cw/RIT's 5 MHz PTO.? I replaced it with a now-obsolete Cumbria X-Lock device. The X-Lock would only lock on some bands.? The root cause is heterodyne crystal leakage through the 6EA8 converter.? That leakage combined with the PTO output results in a waveform that is troublesome to lock.? The solution required a J310 JFET source follower installed ahead of the converter, leaving a pure sinewave into the X-Lock.? While I had difficulty with lock, perhaps converter leakage isn't consistent across all TR-4 models.? ?
I also took advantage of the existing TR-4Cw/RIT circuit and coupled the X-Lock DC output to the RIT control line.? That method eliminates the addition of another varactor diode inside the PTO can.? In fact, there's no connection made inside the PTO can for either the frequency sense or the output control bus.? Lock is extraordinarily good.? From a cold start to hours later, the PTO stays absolutely locked.? The result is so good, I'm going to replace the K4DPK stabilizer in my TR5 with another X-Lock.? Photo below of the X-Lock installed.
Paul, W9AC
Paul Christensen