"Messed up probes are the #1 reason than many otherwise good 410Bs get
junked, which is a shame."

My response might offend the purists, but I can defend myself by stating
that I am just an amateur.

I hate throwing things out. And, I hate spending money on parts that cost
more than the instrument. So, if I had an HP 410 that had a bad probe and I
did not wish to invest in a new tube, I would find a tube that would fit
into the probe and used the appropriate filament voltage. Even a triode can
be used as a diode. The fact that the fitting of the tube might destroy the
frequency response may not be a big factor. Heck, we usually only operate
up to 450 MHz. Even if the calibration is not absolutely correct, it can be
tested easily with a signal generator and calibrated with a calibration
chart. What you end up is a ******* HP 410, which is still better than a
broken one.

I must admit that I have *******ized a lot of things instead of throwing
them out. Some of the stuff I have works better than when it left the
factory. Some does not. In each case, I have outsmarted the trash man.

73, Colin K7FM