AJAZZ AK33 mechanical keyboard
Cheap mechanical keyboard from 2019. I believe there are few different different keyboard models sharing same name - this one is probably one of the earliest and cheapest variant, with mini-USB socket, without backlight and with soldered (not hot-swappable) key switches.
This keyboard is inlucded in https://github.com/SonixQMK/Mechanical-Keyboard-Database.
Initial state: not detected by USB host, not drawing any current from USB, damaged Esc key switch.
Single layer PCB with 0 Ohm resistors used as jumpers.
LEDs and related jumper resistors are unpopulated.
VS11K18A 8-bit microcontroller made by company called Vision. 4k x 16 bit FLASH, 160 x 8 bit RAM, 8 levels stack buffer.
Internal 6 MHz clock, most of instructions are single cycle. Features USB low-speed device and internal 3.3 V regulator.
For a moment I thought that this was problem with MCU soldering, but pins 37...40
are actually internally not connected and intentionally not soldered - this helped with routing
as there are other traces under these pins and silkscreen.
The real problem: bent +5V pin inside mini-USB socket. Keyboard was working after replacing this socket.
AJAZZ branded Cherry MX blue (clicky) clone switches.
Unpopulated transistors driving LEDs.
PCB markings: KM107-18A-VS.
While "wide" keys have switches with different color, I wasn't able to feel
any difference between them.
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