Z88 32kb to 512kb Memory Upgrade

As mentioned in a couple of other posts here, the Z88 is a great machine.  It comes with 32k of RAM, although this can be expanded with plug in cartridges.  An alternative, however, is to replace the internal 32k with something larger.  This photo tutorial shows how you can expand the onboard memory to 512k.

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This involves some pretty hardcore soldering, and is not recommended for your first soldering project.  More importantly, there is some delicate unsoldering too, and if things go wrong, you’ve wrecked your Z88.  You have been warned!

The first thing I should point out that I didn’t come up with this modification myself.  There is an article (long since lost) that has been reproduced on several websites that describes what to do.  It’s quite slim when it comes to photos or clear diagrams though, so basically what I’ve done is just follow instructions, take photographs and write up my experience.

For a copy of the original article, see this link;

http://www.worldofspectrum.org/z88forever/memupgrd.htm

To start with, check the free memory on your Z88.  (There’s technically no reason why you need to do this, but it’ll give you that nice warm fuzzy feeling when you do this again after the upgrade!)

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To see this, push Diamond > E > M > F

I had already done a hard reset (hence the date back to 1987), but 20992 bytes free is about 20K

 

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There are 11 screws (2 hidden under rubber feet and one under the serial number).  They’re all the same size, so no need to worry about remembering which one came from where.

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With all the screws removed the bezel, screen and keyboard lift off of the top.  The ribbon cables to the screen and keyboard pull out, but be careful not to kink or fold them.

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Unclip the battery connectors from the case and lift the motherboard out

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The underside of the motherboard

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The chip highlighted is a 28 pin 32k RAM chip.  This needs to be carefully removed.

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Note that the replacment chip is a 32 pin chip, so you will also need to unsolder the 4 filled holes above.

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Solder in a low profile 32 pin socket.

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Before inserting the chip, bend out pin 1 (top left hand pin) and pin 30 (third one down on the right).  Note where the holes going through the board are marked.  Feed insulated wire through the holes and solder one end to pin 30…

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… and another one end to pin 1

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The other ends goes to two pads by the middle expansion connector.  Do not insert the wire too far in to this hole.

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Reassembly is reverse of disassembly.  When done, check the free memory (diamons > E > M > F) for that nice warm fuzzy feeling in a job well done!

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Comments

  1. I have wanted a Z88 ever since I was knee high to a Spectrum. I finally got the $$$ and found out where I could buy a new one (yay!) The seller told me that I could get an optional 512k upgrade. Wow! Who could turn that down!? He said he had a super tech to do it too. I’m not bad with computers and soldering, especially with neat instructions like the ones you linked to, but I figured, hey, if the guy is a super tech, I won’t get in the way. After all, I wanted this for so long, my Z had to be absolutely perfect! I’m not joking, I spent like 500$ for this setup back in 96, and yes I had a modern computer and a newton at the time.

    A couple weeks later I got my brand new Z88. It was a little quirky, the space key had no play and there was a huge lump under the middle of the keyboard. It was like hitting a table with your thumb every time I wanted to add some space between words. Try doing that 500 times and see how fun it is.

    Apparently this “super tech” put a high profile socket in and actually, get this, actually ran a friggin wire between the mother board and the space bar! Holy mother of…, well, that’s why it didn’t have any play.

    When I contacted the jackass who sold me this ‘amazing’ upgrade. He calmly explained that the keyboard still worked just fine, who needs a key with play in it anyways and that the bump could not be avoided.

    I wanted to die when I found out that this pair of jack@sses disabled one of my internal card slots to do this. F#@ why not just shove a damn 512k cart in it and forget about the whole thing then?!

    *sigh* I have since bought a new Z88 from a reputable English seller, just this year actually, and had the thrill of opening my brand new Z for the first time, sans jackassery.

    I’m glad you have taken the trouble to make this upgrade elegantly. It’s proof that it could be done..well!

    I’m looking forward to your next Z88 projects!

    Posted by Louis Lipp

    Link | November 19th, 2013 at 5:24 am

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