The Museum of HP Calculators

HP Forum Archive 14

[ Return to Index | Top of Index ]

HP-42S and 32KBytes RAM
Message #1 Posted by AlexD30 on 21 Aug 2004, 9:28 a.m.

Hi guys, Where can I get a 32 or 64KB RAM chip to upgrade my HP-42S machine? I've been reading an article about how to do the upgrade job but I have no idea where to get the chip. I would apreciate if you guys tell me how to go about this.

Best Regards,

Alex

      
Re: HP-42S and 32KBytes RAM
Message #2 Posted by Erik Ehrling (Sweden) on 21 Aug 2004, 4:53 p.m.,
in response to message #1 by AlexD30

I use a chip called IS62C256-70U / SO28 made by Issi that I buy from a local electronics dealer. But there surely are several other options, just make sure that it is a 32 kilobyte, low power, 28 pin and in SO package.

Best regards,
Erik Ehrling


PS. Don't forget the Campaign for Emu42! (& Emu48 for Pocket PC)

Edited: 21 Aug 2004, 5:11 p.m.

            
Re: HP-42S and 32KBytes RAM
Message #3 Posted by AlexD30 on 21 Aug 2004, 5:27 p.m.,
in response to message #2 by Erik Ehrling (Sweden)

Thanks, Erik,

I will look around to find a chip and try to do the upgrade myself.

Best Regards, Alex

      
Re: HP-42S and 32KBytes RAM
Message #4 Posted by Randy on 21 Aug 2004, 5:34 p.m.,
in response to message #1 by AlexD30

Try Cypress CY62256L-70SNC.

Digikey 428-1079-ND $3.40 each, in stock at www.digikey.com

These work fine in the 42S.

            
Re: HP-42S and 32KBytes RAM
Message #5 Posted by AlexD30 on 21 Aug 2004, 11:13 p.m.,
in response to message #4 by Randy

Randy,

I ordered the chip at www.digikey.com. Thanks! I will try to do the job my self on my almost new HP-42S.

Best Regards, Alex

      
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

Hi;

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.

My 1.

Luiz (Brazil)

Edited: 21 Aug 2004, 9:16 p.m.

            
Re: HP-42S and 32KBytes RAM
Message #7 Posted by AlexD30 on 21 Aug 2004, 11:09 p.m.,
in response to message #6 by Vieira, Luiz C. (Brazil)

Thank you Luiz, I just ordered the chip from www.digikey.com, thanks to Randy info about. I will try not to destroy my almost brand new HP-42S during process.

Digikey part number: 428-1079-ND $3.40 each, in stock at www.digikey.com

Best Regards, Alex


[ Return to Index | Top of Index ]

Go back to the main exhibit hall