clueless_engineer (Brett)

Another note on the MK-52...
Since proper computers were difficult to save up for during Soviet times (especially for people who didn't have the skills to build one from scratch), a large community was formed around writing and sharing games for the Elektronika programmable calculators.

Hi, I just saw you're designing a keypad for the MK-52. I tried to do the same thing a year ago, but ultimately gave up after two attempts. Here's the first prototype I made:

I just learned this while researching the architecture of the Pentagon-128:

The "Magic" button is used to save a snapshot of the computer's memory contents to disk, like an early "save state" function.

The Pentagon-128 doesn't have a turbo function in its original form, but modifications were developed for adding turbo functionality.

The Astra is based on the "Baltic" clone design, which is well documented around the Internet (mostly in Russian):
zxbyte.ru/baltic_en.htm (in English)
sblive.narod.ru/ZX-Spectrum/Baltik/Baltik.htm
users.atw.hu/zxspectrum/index.html (in English)

I thought I'd share some tips for designing keyboard PCBs:

• The standard spacing between Cherry MX keyswitches is 19.05mm. You can achieve the "staggered" layout seen on most keyboards by using a 4.7625mm grid (1/4 of 19.05mm). In KiCad, the "Edit Grids..." option in the grid selection menu can be used to define custom grids.

Hi, you mentioned in a recent video that 14.000MHz crystals are hard to find nowadays.
I have some good news; LCSC sells them in lots of 5 for US$0.26.