hello,
i find a post saying that use of AA 1.4 volt cells could damage the contact by breaking them,
in my opinion it is true but i find a method to avoid that,
use a hammer to stike lightly on the positive end of the cell will crush (make it flat) it in a way it will not hurt the connection on the HP , so the 1.5 volt will have same length that the 1.2 volt rechargeable batteries.
After doing that check that cell as no leakage.
it works great.(i made it using energizer cells)
power is 3V with two cells ,i assume that it is not too much for calculator as a lot of people use it without having reported problems other than the possible breaking of batteries contact which can be avoided with this method.
another issue i had with my hp 34c is the misfunctionning of a key (the dot key) ,after opening calculator i find there was a contact problem in the plastic bubble containing contacts for this particular key as the others keys on column and row of the dot key was working well,even if the aluminium of contact seems perfect,it needed an extra pressure, adding 4 or 5 peice of sticking paper beetween the bubble and the key solve the problem .
note that this method is working for a solderless unit
regards,
damien