|Re: HP-42S and 32KBytes RAM|
Message #6 Posted by Vieira, Luiz C. (Brazil) on 21 Aug 2004, 9:15 p.m.,
in response to message #1 by AlexD30
I upgraded five HP42S so far. The one that's still with me (and one of the others) uses the 32KRAM chip removed from one old HP48G:
MT62C256F-70LL (by M?T... the mid character is a logo. a circle with a tic-tac-toe symbol inscripted on it)
The other one seems to have a different code, but I don't have it with me anymore.
The most interesting "origin" for these RAM chips is a PC-compatible sound board. It had three 32KRAM chips, and I used two of them so far. The third one I keep as a "spare", just in case. The code for these chips is:
W24257S-70L (by Winbond)
I am not sure this is a low-power RAM chip, but I have not noticed any reduction in battery life time. Unfortunately, I have none of these chips in working calculators so far. The fifth HP42S I upgraded has another chip with a different code, but I didn't find my notes about his one. Sorry!
I know new IC's are a far better choice, but in the case you have the source and are willing to try... Just keep in mind that it is always a good idea to test the chips before doing the "transplantation". Except for one of the units I upgraded (the first one, my own), all others needed to be opened and repaired somehow. So I took the chance to upgrade. Now that we're talking, I kept all of the 8KRAM chips in a safe place for whatever use later... and now they are, at least, five! Where in the h..l did I save them? Well, that's another history.
Edited: 21 Aug 2004, 9:16 p.m.