[HP-48GX] Expansion slot info needed

[Kikicat123]

Hello all, First time posting here so I hope I got the correct place in the forum.

I want to make my own 128K RAM card because the ones I can find second-hand are incredibly expensive, and as far as I can tell there isn't anyone making new ones. I have been able to find a pinout for the expansion cards, however I am missing a few crucial details:

• I need the physical dimensions of the cards themselves - Width, Height, and also Thickness.
• Additionally, I also do not know what the voltage is going to the cards, only that it is VDD.
• It would also help if someone could measure the power draw of one of the cards while in use - This will let me see how much power I can pull from VDD.
  

Also, is it worth trying MRAM (Magnetoresistive RAM) as a non-volatile replacement for a SRAM chip? If it worked, it wouldn't need a battery, at least in theory.

Thanks,
Robert

[rprosperi]

Retrotronik in Portugal makes and sells cards in 128KB, 1MB and (eventually) 2MB sizes, at quite acceptable prices:

https://retrotronik.com/

Note that sometimes it takes a while to get replies, so be patient, you will get a reply.

If you proceed to making a card I strongly suggest you get your hands on a actual card (buy a dead one) as the keying for the channel where the connector mates deep within the slot is neither documented well nor easily described. This unexpected aspect has foiled more than one DIY-er attempting to make 48 cards.

Good luck

[Jeff_Birt]

There are multiple RAM card projects with gerber files here: https://www.hpcalc.org/hp48/docs/misc/

[Kikicat123]

(10-27-2023 12:05 PM)rprosperi Wrote:  Retrotronik in Portugal makes and sells cards in 128KB, 1MB and (eventually) 2MB sizes, at quite acceptable prices:

https://retrotronik.com/
Note that sometimes it takes a while to get replies, so be patient, you will get a reply.

If you proceed to making a card I strongly suggest you get your hands on a actual card (buy a dead one) as the keying for the channel where the connector mates deep within the slot is neither documented well nor easily described. This unexpected aspect has foiled more than one DIY-er attempting to make 48 cards.

Good luck

I do still plan to make a card, mainly for the novelty of having made it myself. Ill be sure to take this into account - I have yet to find a dead card I can buy to use as reference. I'll see if I can get one of those Retrotronik cards, otherwise I think I'll be forced to find something else for much more expensive.

Thanks a ton for the info!

Jeff_Birt Wrote:There are multiple RAM card projects with gerber files here: https://www.hpcalc.org/hp48/docs/misc/

Thanks for the link, I'll take a look.