Backup battery

[Terry Bowman]

>A general question: can I replace NiCads that are used for static RAM backup
>with something better, such as Lithium cells, without modifying the charging
>circuit?
>
>(The instruments in question are polysixen BTW -- notorious for having their
>backup NiCads blow up and belch all sorts of corrosive spew over the PCBs. :)
>
>The voltages are a bit off as well -- the original design has a three-pack
>of NiCads, making 3.6 volts, and the Lithiums are what, three volts each?

Jens,

By far the easiest thing to do is remove the NiCd's, disable the charging
circuit by removing the blocking diode or current-limiting resistor, and
replace the whole mess with a couple of name-brand alkaline batteries in
plastic holder stuck onto the PC board with double-sided tape. This is what
a lot of pinball enthusiasts are doing these days (I've seem more than one
Bally logic board completely eaten up--that's what happened to my KISS
machine). You just have to remember to replace the batteries every five
years or so--the ones they make these days should last that long.

Terry Bowman, KA4HJH