| The pack you have is either NiCad or NiMH, most probably NiCad.
Almost certainly NiCd.
| As the | chargers (especially 18 years ago) were different (the charge cycle is | different for the two types),
Only for fast chargers. For slow chargers, it's basically the same -- put X mA into the cells forever (as long as the charger is on, anyways.)
| you should try and replace the pack with the same chemistry.
Not bad advice. | Unfortunately, you won't find many NiCad packs around nowadays.
Sure you will. | You may need to get a NiMH pack and a new charger (same voltage / cell | as NiCad = 1.2V per cell nominal).
If it's a slow charger, it'll work. It'll just take a lot longer to do a full charge ... perhaps 3 to 4 times as long, because NiMH cells will have 3-4 times the capacity. | The batteries are clearly a series arrangement (1.2V x 5 = 6V), so a | charger designed for 5 cell NiMH would work.
In any event, it's relatively easy to make a new pack if you're good at soldering.
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includes some instructions.
You can find 4 packs of AA 900 mAh NiCd packs at Wal Mart or Home Depot for about $6 each. Or NiMH packs will probably work as well.
Or places like Batteries Plus can make you a new pack. You'll pay more, but probably less than you'd pay the original manufacturer for a new battery pack.