Best solution for expanding ram to 128k on a zx48k?

[ilove8bits]

I also realised the ram chip(s) are not the problem, but the logic is. There seems to be GALs available on Ebay, but the mileage might not be perfect with some of them... I found this "universal" 128k rebuild:

https://hw.speccy.cz/128krebuild.html

and this external one:

https://velesoft.speccy.cz/zx/external_ ... /index.htm

They both use GALs.

I'm really not sure (or technically competent enough) to evalute how I want the ram to be configured (ZX Spectrum 128k (Toastrack)/+2 (grey) or ZX Spectrum +2A / +2B (both in a black case) or a +3 / +3B). Could you please enlighten me on this? I just thought "if there's 128k ram, then there is

Thanks one again Mark for your time helping others out

Hi,

Apologies in advance if digging up an old thread is bad etiquette.

I've built this internal 128k upgrade into my spectrum issue 2 (16K) a few years ago and rehoused it into a 48k+ case. It was dead anyway, so I had nothing to lose, I needed to replace the lower rams anyway, so I socketed them.
For the upper ram I used the 48k upper ram replacement from retroleum, which is actually a full 64K (it has to account for both types of faulty upper ram) and works well with this upgrade.
As usual life got in the way & I also had some bug with the first Bank [1] of the ram which took a while to figure out. In the end I added a 100nF capacitor across the bottom pins of the GAL (pins 12 & 13). I only noticed the problem disappeared when i put my multimeter probe on pin 13, so I assume its "noise" and added that capacitor.
On the website https://hw.speccy.cz/128krebuild.html there's a note about memory errors and changing C64 for issue 2 boards, however this didn't help. (the extra capacitor across the GAL did)

Also, he has another website (and blog) that shows in more detail the internal upgrades inside some rubber key issue 2's.
https://z00m.speccy.cz/?file=galleries

I also had built the AY8912 external and that was working well too, until I saw the vLA82+ with built in AY sound! It also has RGB or composite out.
www.vretrodesign.com/products/vla82s-wi ... -interface
I did have the S-video replacement to stop the dot-crawl, but my TV's were fussy with S-Video, so that RGB was the way to go for me.

If you need any help with the upgrade, just ask.

[1024MAK]

Hello ilove8bits

Welcome to the forum

Apologies in advance if digging up an old thread is bad etiquette.

Apart from another member who has a fault on their computer/expansion, jumping on to an existing topic where the original member is also talking about a fault on their computer/expansion (where it can become confusing, hence we much prefer they start a separate topic), we are relaxed here about adding to old threads/topics.

And it’s especially helpful to add to an existing thread/topic if you are bringing new, or helpful information
So please carry on…

Mark