Hardware errata

Rev 1

R307 needs more clearance from D400
Pins 1 and 12 of U502 need pull-downs
Pin 1 of U501 needs pull-up
D203 reversed polarity
R236 and R234 are swapped
Q301 needs to be NPN, change to BC817
increase R307 -> 3.3Kohm and increase R500 -> 33Kohm
C201: oscillates at 0 and 1nF, stable at 100nF
add clamp diodes to GND on op-amp outputs to ADC when op-amp has negative supply
R214 -> 4.7k
LM339PT is in TSSOP package. Change for SOIC P/N
GDT200 minimum firing voltage is too low
the relay model should be changed to 9001-05-00. 9001-05-02 is an undocumented normally closed variant.
D504 should follow the schematics in its datasheet
R502 should be connected to VCC
R502 -> 240 ohm
R234 -> 7.5k
Q104 -> DMN3404
R114 -> 470 ohm
R115 -> 4.7k
R227 -> 470 ohm
R228 -> 4.7k
review values of R226 and R113
use crystal type recommended by the MCU datasheet
fix filament voltage protection threshold
22k FBI current resistor -> 10k?
add connector for OLED display?