Memory upgrade for 42s


I just saw a posting on Ebay for a 42s with an optional upgrade to 32K being offered.

I had not heard of this type of upgrade before, but it seems like it might be kind of useful. What is the story and what is involved?



Our very own Randy Sloyer does this (has done both of mine) quite well. lookin the articles and contacts areas of the museum.

It's a straight desolder/solder operation, but I have say that randy does a very sweet job of it and I'd send mine off to him (again) in a hearbeat.

now.... to get my 48SX machines upgraded....


What is Randy's email address. I can't seem to find it.


How much does it cost to have this procedure done?

Much obliged!



Paul has described the procedure here.



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.

Best regards.

Luiz C. Vieira _ Brazil


Hey gang, thanks for the praise, but it should go to others. I was just last man in.

The real credit for all the work goes to Paul Brogger for taking the time to explain how to open a Pioneer and solving the original 32K puzzle. Tony Duell helped out with some surface mount rework info.

It is all in the archives, I just read 'em and followed their paint by number instructions. A real no-brainer if you're handy with a soldering iron. They made it sound easy, because they did all the hard work to make it that way.


Hi, Randy;

once again, thank you for reminding me.

At the time I read about the HP42S' 32KRAM expansion I remember contacting Paul Brogger and asking him about compatible IC's for the expansion procedure. He made a research and returned me some info about the 32KRAM chip used in the HP48G. I had some "hard" (not hardware) problems and my e-Po.Box was stuck with many old e-mails. I had to make a deep cleanup and I did it based in time "slices". Many, many good information was lost, except for almost all attachments. Golden information and very important reference were definitely lost, and I remember having Paul Brogger's mail dated a bit far from now. I have probably lost it.

Well, what else to do? Now I can access Internet and I was not able to do it a few days ago.

So, please, I hope Paul forgive me for being not polite. There are so many good, expert professionals contributing here at this forum that we sometimes loose track.


Luiz C. Vieira - Brazil


For my part, thanks to you all.

Actually, Tony Duell happened to mention the possibility of an upgrade once, and as I'd already been "inside" my 42S, I followed up on it. Tony provided all of the essential details.

So, without Tony's knowlege and experience, the story may never have been told . . . As to my part, I must say I was (and am) just having fun!

Relating to another recent string of posts ("LOUD APPLAUSE"), it is marvelous that this site is available for the gathering of the scattered few who share an inordinate interest in a quirky corner of late-20th-Century technology. And I'm glad to have been able to make a small contribution.

Possibly Related Threads...
Thread Author Replies Views Last Post
  Almost totally OT: Looking for Sharp EL-9900G ROM upgrade Marcus von Cube, Germany 3 769 03-03-2013, 09:35 AM
Last Post: Marcus von Cube, Germany
  HP10BII+ question (ROM upgrade is possible?!?) Csaba Tizedes (Hungary) 6 1,077 02-21-2013, 05:19 PM
Last Post: Eric Smith
  41 User Memory vs System Memory Gerry Schultz 6 1,141 07-01-2012, 12:02 AM
Last Post: Monte Dalrymple
  [WP-34S] Upgrade in 10 mins. now v 3.1 2988 Chris Tvergard 12 1,805 06-01-2012, 02:39 AM
Last Post: Walter B
  HP-41C pcb connector upgrade Hans Brueggemann 6 1,155 05-19-2012, 10:17 AM
Last Post: aurelio
  USB-41 status update: Upgrade available v3.0 Diego Diaz 2 649 04-24-2012, 07:50 AM
Last Post: Diego Diaz
  42s questions and 42s vs 35s snaggs 13 2,437 09-19-2011, 02:44 AM
Last Post: snaggs
  HP 50G - ROM upgrade under Linux Glenn Becker 6 1,031 07-10-2011, 06:22 PM
Last Post: Glenn Becker
  42s upgrade Paul Dale 22 2,436 05-16-2010, 02:38 PM
Last Post: geoff quickfall
  Upgrade to HP Museum DVD Set Version 7.0 Gerry Schultz 1 535 12-01-2009, 06:31 PM
Last Post: Walter B

Forum Jump: