"dansawyeror" wrote in message
...
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

Hi Dan
I picked the 8405 out of a dumpster at a mil surplus place. Actually I
picked out two HP 8405A Vector Voltmeters. One is complete. The other had
one of its probes severed and I couldnt find that probe. I will try to
build two probes on boards with a BNC in place of the pointed probe.
I dont anticipate being able to make this Voltmeter an accurate
instrument. So, I wont be able to offer any data that anyone else would
want.

Jerry