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

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

Thanks to David DiGiacomo I've got the info and it looks like the B+ is 5.4
VDC at 5.5 ma and the B- is 8.1 VDC at 20 microamps! HP used a small
centrer tapped transformer at about 25 volts that was regultaed down to the
8.1 and 5.4. I can't find anything on the physical size of the xfrmr but it
has to be no bigger than end of ones thumb,but maybe they used a wall wart
but I kind of doubt it. I've not had any experience with real small low
current xfmrs that take 115VAC to 20 or 30 VAC and would appreciated any
ideas on what to use. A wall wart would be my last resort.
tnx
hank wd5jfr
"Henry Kolesnik" wrote in message
...
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

"Henry Kolesnik" wrote in message ...
Thanks to David DiGiacomo I've got the info and it looks like the B+ is 5.4
VDC at 5.5 ma and the B- is 8.1 VDC at 20 microamps! HP used a small
centrer tapped transformer at about 25 volts that was regultaed down to the
8.1 and 5.4. I can't find anything on the physical size of the xfrmr but it
has to be no bigger than end of ones thumb,but maybe they used a wall wart
but I kind of doubt it. I've not had any experience with real small low
current xfmrs that take 115VAC to 20 or 30 VAC and would appreciated any
ideas on what to use. A wall wart would be my last resort.
tnx
hank wd5jfr
"Henry Kolesnik" wrote in message
...
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



FWIW, Henry, I prefer to use an AC output 'wall wart' and install in
the unit to be powered a pair of diodes to supply + and - which I
filter and regulate down to what is needed. For that miniscule power
demand the filter caps and TO-92 regulators will take up little room.

Neil S.