|Re: OT - recharging NiCad in a Commodore SR4190|
Message #9 Posted by Daniel Baum on 3 Nov 2006, 4:30 a.m.,
in response to message #8 by Katie Wasserman
I have 3 of these rather magnificent Commodore calculators with rechargeable batteries - an SR4190R, an SR9190R and an SR1400. They are all very impressive, subject to the limitations mentioned above.
However, when you replace the rechargeable batteries they ALL have a very serious problem - the power wires break off right at the end. I have just attempted to replace the apparently original batteries of the SR1400, which were very leaky, but failed because the negative battery wire broke off right at the mother board, presumably as a result of the corrosion from the battery. I have no idea how to prevent this and am unable to repair it once it happens. Exactly the same thing happened with the SR9190R.
The only machine whose batteries I successfully replaced was the SR4190R. On that machine, the mains power wire broke off at the socket, and I was able to solder it back on.
The only consolation is that it is apparently safe to operate them from an off-the-shelf variable power supply, set to about 4.5V. Do not use the original charger and do not attempt to blast them with too much voltage. The SR-1400 seems to be more sensitive and to require less power, possibly because it seems not to have a voltage regulator.