Hank,

According to my 1967 HP catalog (in surprisingly good
condtion, by the way) the 456A uses two TR233R's and one
TR234. It does not list current required (and I guess
the 1977 catalog does'nt either.)

My catalog also estimates battery life at 400 hours.

You might search the net for mercury battery current
capacity. I seem to recall it is somewhat less than
nicads, but I don't remember the ratios.

73,

Phil - N4GWV


"Henry Kolesnik" wrote in
:

I just got this HP 456A AC Current Probe and need some help to get it
going. The 1977 HP catalog indicates that it could operate 400 hours
on batteries, not very long for what's in it. The dead batteries that
came with it are Mallory TR 236R at 8.1 volts and TR 234R at 5.4
volts, these are C size diameter. There are only two 2N5087
transistors, a diode, and a few resistors and capacitors in the
circuit, what's the current draw? I am not sure that these are the
correct batteries but would like to know if anyone out there can be
confirm the batteries or has a schematic, manual or AC power supply.
If I can't find an HP optional AC supply I think I'll build a little
Zener stabilized supply after I get the voltages confimred. tnx
Hank WD5JFR