Jerry,

I have just completed bringing an 8405a back on line. The BAMA copy is mostly
readable and certainly useable. My unit had a bad probe and a bad pulse
amplifier. Otherwise it aligned very well.

The probes are managable to work. I ended up buying an .024 PC bit to clean the
solder holes. This allowed placing the diodes directly and then soldering them.

The detected phase angle appears to be dependent on having a matched sampling
efficiency between the probes. This is certainly level sensitive and may be
frequency dependent. I have tried several diodes including the origenal HP diodes.

I use a DVM to measure diode forward voltage drop. The origenal diodes measure
about 390 mv. NTE584s measure about 420 mv and can be tuned to match at about
98%. This in practice is usable. 1n5711s measured about 440 mv and can be tuned
to match to about 90%. The instrument will appear work but the phase angles are
incorrect due to the sampling errors. I am still looking for a better choice
then the NTE584s.

Let us know what you find out. - Dan

Jerry Martes wrote:
Can anyone tell me where I can get a schematic of the probe for the HP
8405 Vector Voltmeter?

Thanks
Jerry