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HP 456A ??

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

Reply to
Henry Kolesnik
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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 news: snipped-for-privacy@corp.supernews.com:

Reply to
Phillip Jockell

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

going.

batteries,

not

build

Reply to
Henry Kolesnik

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.

Reply to
Neil S.

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