Posts: 189
Threads: 23
Joined: Jan 1970
i found a better way to replace the pack batteries than
cutting the side of the plastic. here:
http://www.voidware.com/calcs/woodstock_repairs.htm
this page is not finished. i'm still repairing the keyboard :-)
good luck.
Posts: 883
Threads: 17
Joined: Feb 2006
The original HP AA nicads were 700 mah. These are still made by Sanyo, see the pages here on batteries. You can sub 1100 mah nicads as well, just allow for 50% longer charging times.
You can of course use alkaline and lithium AA's - but under no circumstances should the charger be anywhere near the unit when you do this.
You can also use the super-extended capacity ni-mh rechargeables at 1850 mah - but you must recharge externally. This is really the best way to preserve your 21 or any woodstock as plugging in a unit with a dead or missing battery is the most common way to kill it.