Thanks. I still have a large bag of HP 5082-2800 glass diodes here in a little HP envelope dated 1974. There were originally 250 diodes in it but it's down to about 50 now.?
Once I know the HP 8405A is mine (I've made an offer) I plan to remove a good diode from the good probe and measure it on a curve tracer and also measure it on a VNA.
I've measured the input impedance of the probes across 2-1000MHz and it's easy to spot that the repaired probe has too much capacitance and the Rp is much lower up at VHF and into UHF.
I need to find diodes that give the correct input Cp capacitance and Rp resistance vs frequency when fitted to the probe.
I also need to check out the good P JFET on a curve tracer and measure its s-parameters using a VNA up to 1GHz or so. I've done this many times for N channel JFETs but not P channel.
