(Q_and_a)
Item: 102 by akcs.getz@hpcvbbs.cv.hp.com
Author: [Robin Getz]
  Subj: fix for smith corona ram cards?
  Date: Fri Jan 10 1992

Hello Hp.

I was wondering if you could tell me if, or how this could damage my 48.

I realize there are some voltage regulation problems with non-HP ram
cards (low voltage shutdown threshold).  [Note: For details about this
problem, see MEMCARDS.DOC on Goodies Disk #3.  -jkh-]  I think I have
found a way to bypass this problem.

There is a control line going to the I/O chip from the voltage
regulator. This line is Vcc until Vcc is lower than 4.1V (on the card
I ripped apart) then it slams to zero, just as you said it would in
all the other documentation you have previous posted on this subject.
What I have done is disconnect this line from the voltage regulator
and reconnect it to Vcc.  Now the card will not shut off until Vcc
reachs card battery voltage (about 3.0 V).  Is not this what we want?

I have this card in my calculator (rip up my warranty card please) and
it works fine.  I have put nearly dead batteries in my calculator to
simulate low voltage conditions and it works just fine.

Before I run around and start telling everyone which connections to
change I thought I would give you the first kick at the cat (per say).

Robin Getz
Electrical Engineer
University of Saskactchewan
873398@bell.usask.ca

If you would like I can send you the changes I have made in order for you
to test in your labs.

[Note: This interesting posting brought a few responses from others,
and no objections from HP....  -jkh-]