Electrical failure caused issues on heater 2 channel

[JairoRB]

Hello.

I am using the Duet 2 Wifi with 2 DyzeEND-X and DyzeExtruders which are working just fine. I needed to get 12v from the board, so I connected a LM2596 based step down buck converter to get 12V. However, while I was tuning the potentiometer to get the desired 12 volts, something shorted (maybe?).

There were some sounds that sounded like shorts, but no sparks or anything similar. I instantly turned everything off, and did a visual inspection. Nothing looked burnt at all, nothing was abnormally hot. Disconnected the buck converter, turned everything back on and everything was working perfectly from the dashboard, except for the heater 2 temperature readings. It is stuck reading about 1100-1400°C while heater 1 reads about 25°C, ambient temperature. I disconnected the thermistor and switched ports, and yet again it was heater 2 reading 1400°C. The thermistors themselves are not the issue, I think, so I believe something did burn.

I am not sure tho, how does everything else work except the temperature readings from heater 2? I would've thought that many more things would be destroyed before it got to the thermistor channel.

This is the config.g:

; Configuration file for Duet WiFi (firmware version 2.03)
; executed by the firmware on start-up
;
; generated by RepRapFirmware Configuration Tool v2.1.3 on Thu Nov 28 2019 14:12:19 GMT-0600 (Central Standard Time)

; General preferences
G90                                             ; send absolute coordinates...
M83                                             ; ...but relative extruder moves
M550 P"CubeProEIE"                              ; set printer name

; Network
M551 P"delta"                                   ; set password
M552 S1                                         ; enable network
M586 P0 S1                                      ; enable HTTP
M586 P1 S0                                      ; disable FTP
M586 P2 S0                                      ; disable Telnet

; Drives
M569 P0 S1                                      ; physical drive 0 goes forwards
M569 P1 S1                                      ; physical drive 1 goes forwards
M569 P2 S1                                      ; physical drive 2 goes forwards
M569 P3 S1                                      ; physical drive 3 goes forwards
M569 P4 S1                                      ; physical drive 4 goes forwards
M584 X0 Y1 Z2 E3:4                              ; set drive mapping
M350 X16 Y16 Z16 E16:16 I0                      ; configure microstepping without interpolation
M92 X87.90 Y87.90 Z1066.60 E420.00:420.00       ; set steps per mm
M566 X900.00 Y900.00 Z12.00 E120.00:120.00      ; set maximum instantaneous speed changes (mm/min)
M203 X15000.00 Y15000.00 Z1200.00 E1200.00:1200.00 ; set maximum speeds (mm/min)
M201 X500.00 Y500.00 Z250.00 E250.00:250.00      ; set accelerations (mm/s^2)
M906 X1500 Y1500 Z800 E800:800 I30              ; set motor currents (mA) and motor idle factor in per cent
M84 S30                                         ; Set idle timeout

; Axis Limits
M208 X0 Y0 Z0 S1                                ; set axis minima
M208 X200 Y270 Z190 S0                          ; set axis maxima

; Endstops
M574 X1 Y1 Z1 S0                                ; set active low and disabled endstops

; Z-Probe
M558 P0 H5 F120 T6000                           ; disable Z probe but set dive height, probe speed and travel speed
M557 X15:200 Y15:195 S20                        ; define mesh grid

; Heaters
M140 H-1                                        ; disable heated bed
M305 P1 T4606017 B5848 C5.548428e-8 R4700       ; set thermistor + ADC parameters for heater 1
M307 H1 A580.4 C256.6 D6.4 S0.50
M143 H1 S490                                    ; set temperature limit for heater 1 to 490C
M570 H1 P4 T25 					; Allow 25°C variation from setpoint  
M305 P2 T4606017 B5848 C5.548428e-8 R4700       ; set thermistor + ADC parameters for heater 2
M307 H1 A580.4 C256.6 D6.4 S0.50
M143 H2 S490                                    ; set temperature limit for heater 2 to 490C
M570 H2 P4 T25 					; Allow 25°C variation from setpoint  

; Heated chamber
M141 H3 ; Assign chamber heater to heater 0
M143 H3 S100 ; Set temperature limit for heater 0 to 120C
M307 H3 A50 D60 B1 ; use bang-bang control for the chamber heater with 60 seconds dead time
M305 P3 T100000 B4400 C9.486166e-8 R4700 ; Set thermistor + ADC parameters for chamber

; Fans

; Tools
M563 P0 S"Extrusor 1" D0 H1 F0                  ; define tool 0
G10 P0 X0 Y0 Z0                                 ; set tool 0 axis offsets
G10 P0 R0 S0                                    ; set initial tool 0 active and standby temperatures to 0C
M563 P1 S"Extrusor 2" D1 H2 F0                  ; define tool 1
G10 P1 X0 Y0 Z0                                 ; set tool 1 axis offsets
G10 P1 R0 S0                                    ; set initial tool 1 active and standby temperatures to 0C

; Custom settings are not defined

And here are the best pictures I could the of the board.

There's a bit of gunk from adhesive / hand grease on the bottom side, that's not burn marks or anything like that.

Any ideas? Thank you