|Re: hp34c compatible charger?|
Message #4 Posted by Tony Duell on 2 Aug 2004, 2:04 p.m.,
in response to message #3 by db (channeling Norm again)
The internal charger circuitry of the Spice (HP31E, HP32E, HP33C, HP33E, HP34C, HP37E, HP38E, HP38C) and Woodstock (HP21, HP22, HP25, HP25C HP27) is identical (consisting essentially of a diode and an 8.2 Ohm resistor). The external transformers also have much the same characteristics.
You could therefore use the charger from a Woodstock machine if you changed the output connector (e.g. by using the cable/plug from the charger that came with your 34C). There are 2 versions, the -B is supposed to be used with models with continuous memory. It has a couple of zener diodes in inverse series across the output (I think they're about 18V each), to remove voltage spikes that could corrupt the continuous memory.
Please also read the warnings about charging batteries in continuous-memory Woodstock and Spice models. If the battery pack goes open-circuit, the RAM chip (HP custom, almost impossible to find) can be destroyed. The safest way is to use the reserve power pack, but the one for Spice models is particularly hard to find. Alternatively you could use a non-continuous-memory machine -- even a non-working one -- to charge your battery pack.