When I started designing Z20X, one of my major goals was to make it as DIY-friendly as possible. Hence all components are carefully selected to be through-hole (with one exception!), and a few as they can be without compromising the integrity of the system. The only SMT component is the eZ80 processor, which is only available as 100-pin TQFP package with 0.5mm pitch between the pins. It can be a bit challenging for assembly by a novice or without a good pair of tweezers and a magnifying glass, but certainly doable. There are many online video guides how to painlessly solder this type of components. In any case I strongly recommend the SMT IC to be the first one soldered on the board.
As a backup option, the board has holes for optionally installing four 26-way dual row female connectors in the standard 2.54mm (0.1”) pitch. These four connectors form a 104-pin PGA socket for pre-assembled processor modules. Such processor modules can be installed to replace the default eZ80, or to supply a processor to the system in case the IC is not installed. The additional benefit of this approach, is that future modules with processors other than eZ80 can be installed as well.
The schematic is shown in the picture below. For better clarity, it can be also downloaded as a .
In addition to the schematic, a separate file can be downloaded to help with the component positions on the board. In most cases however, this additional file is not needed since all component values are already labelled on the PCB.
It is important to not forget that the connector to the LCD is on the bottom side of the board.
There is also a third file with the Bill of Material (BOM), variant , and another variant , both with references to order positions from . The only two exceptions are the Yamaha OPLL YM2413B (or YM2413), which is an old IC which can be found only on the secondary market, and the LCD panel module, which is only available from various unknown Chinese manufacturers. Both these parts can be purchased (with a bit of extra care to avoid fakes for the Yamaha chip) from .