|Re: Memory upgrade for 42s|
Message #6 Posted by Vieira, Luiz C. (Brazil) on 5 Mar 2003, 1:02 a.m.,
in response to message #1 by John Cadick
I have two HP42S and I upgraded one of them to 32KRAM. The goal is to replace the internal 8KRAM chip for a compatible 32KRAM. As expected, the 32KRAM is 4 X the 8KRAM and needs at least two new terminals to encode the other "three" banks (just a figure). The replacement I found had four extra pins, just for keeping package standards.
The HP42S all-board already has the pin layout ready to accept the new 32KRAM chip. There are just twou "jumppers" that must be changed: open the closed one, and close the openend one. If you are willing to do it, let the guys here guide you.
I must (as always) mention that Randy Sloyer guided me in the replacement procedures, but others in here (please, forgive-me; I don't remember who discussed the replacements with me some mnths ago. I'd liek to be fair in my credits...) ar also aware of the changes.
AFAIK, the best/safest replacement, when available, is the HP48G's 32KRAM chip (the GX/G+ is 128 and will not fit in place). I take this as a reference, but for sure there are other compatible RAM chips. I just don't know them.
The worst part (because it's a bit risky) is openning the calculator. There are four (or six?) heat-shaped rivets that lock the keyboard (lower part) and they are somewhat hard to "crack". The four ones under the IR lens/battery door are easy to "open/remove".
others will post, for sure. This is my US$0.05 contribution.
Luiz C. Vieira _ Brazil