[rwmj]

Most likely the 16K "rampack". It was pretty much essential to get anything done with the machine[1]. The rampack infamously suffered from "rampack wobble" where a slight movement of the machine would disconnect lines between the motherboard and the rampack causing a crash. Eventually I got a larger case/keyboard and mounted the rampack internally.

[1] Though there was 1K chess, a mostly complete chess game in 672 bytes https://en.wikipedia.org/wiki/1K_ZX_Chess

[pienight]

That was it! And I remember the wobble well. Had it set up on the kitchen table and the slightest knock would screw everything up. Good times.

[Chris_Newton]

The rampack infamously suffered from "rampack wobble" where a slight movement of the machine would disconnect lines between the motherboard and the rampack causing a crash.

Oh, that wobble! Definitely on my short list of the most annoying hardware problems in computing history. You’d spend ages typing in the code for a game from your book, and then just as you were ready to go…

[FabHK]

Did teach you to save frequently though, on cassette tape, which only took a few minutes! :-)

[Chris_Newton]

Cassette tape? We didn’t have such luxuries until we got an Acorn Electron a few years later! So jealous. :-)