Phase A and B may be disconnected

[Chownki]

Hey - Got an older prusa mk2.5s with a duet 2 wifi, it have been running fine for months, but now when im doing G32 ill get "Warning: Driver 0 warning: phase a may be disconnected, phase B may be disconnected"
Driver 0 is my X axis and its running fine. I have checked all wires and connector all seems fine, not sure what else to look for?

m122
=== Diagnostics ===
RepRapFirmware for Duet 2 WiFi/Ethernet version 3.4.0 (2022-03-15 18:58:31) running on Duet WiFi 1.02 or later
Board ID: 0JD0M-9P6B2-NJ4S4-6J9F8-3SD6S-TV1GM
Used output buffers: 3 of 24 (14 max)
=== RTOS ===
Static ram: 23868
Dynamic ram: 74768 of which 12 recycled
Never used RAM 10432, free system stack 118 words
Tasks: NETWORK(ready,32.5%,243) HEAT(notifyWait,0.1%,332) Move(notifyWait,0.0%,295) MAIN(running,67.4%,460) IDLE(ready,0.1%,30), total 100.0%
Owned mutexes: WiFi(NETWORK)
=== Platform ===
Last reset 02:08:50 ago, cause: power up
Last software reset at 2022-05-11 20:30, reason: User, GCodes spinning, available RAM 13360, slot 1
Software reset code 0x0003 HFSR 0x00000000 CFSR 0x00000000 ICSR 0x0041f000 BFAR 0xe000ed38 SP 0x00000000 Task MAIN Freestk 0 n/a
Error status: 0x00
Aux0 errors 0,0,0
Step timer max interval 0
MCU temperature: min 24.8, current 35.5, max 39.4
Supply voltage: min 10.6, current 12.1, max 12.5, under voltage events: 0, over voltage events: 0, power good: yes
Heap OK, handles allocated/used 99/0, heap memory allocated/used/recyclable 2048/108/108, gc cycles 0
Events: 7 queued, 7 completed
Driver 0: standstill, SG min 0
Driver 1: standstill, SG min 0
Driver 2: standstill, SG min 0
Driver 3: standstill, SG min n/a
Driver 4: standstill, SG min 0
Driver 5:
Driver 6:
Driver 7:
Driver 8:
Driver 9:
Driver 10:
Driver 11:
Date/time: 2022-05-12 19:12:06
Cache data hit count 4294967295
Slowest loop: 11.25ms; fastest: 0.19ms
I2C nak errors 0, send timeouts 0, receive timeouts 0, finishTimeouts 0, resets 0
=== Storage ===
Free file entries: 10
SD card 0 detected, interface speed: 20.0MBytes/sec
SD card longest read time 4.0ms, write time 0.0ms, max retries 0
=== Move ===
DMs created 83, segments created 6, maxWait 429259ms, bed compensation in use: none, comp offset 0.000
=== MainDDARing ===
Scheduled moves 244, completed 244, hiccups 0, stepErrors 0, LaErrors 0, Underruns [0, 0, 1], CDDA state -1
=== AuxDDARing ===
Scheduled moves 0, completed 0, hiccups 0, stepErrors 0, LaErrors 0, Underruns [0, 0, 0], CDDA state -1
=== Heat ===
Bed heaters 0 -1 -1 -1, chamber heaters -1 -1 -1 -1, ordering errs 0
=== GCodes ===
Segments left: 0
Movement lock held by null
HTTP is idle in state(s) 0
Telnet is idle in state(s) 0
File is idle in state(s) 0
USB is idle in state(s) 0
Aux is idle in state(s) 0
Trigger is idle in state(s) 0
Queue is idle in state(s) 0
LCD is idle in state(s) 0
Daemon is idle in state(s) 0
Autopause is idle in state(s) 0
Code queue is empty
=== Network ===
Slowest loop: 15.71ms; fastest: 0.00ms
Responder states: HTTP(2) HTTP(0) HTTP(0) HTTP(0) FTP(0) Telnet(0), 0 sessions
HTTP sessions: 1 of 8

• WiFi -
  Network state is active
  WiFi module is connected to access point
  Failed messages: pending 0, notready 0, noresp 0
  WiFi firmware version 1.26
  WiFi MAC address e0:98:06:22:e6:1c
  WiFi Vcc 3.39, reset reason Turned on by main processor
  WiFi flash size 4194304, free heap 24800
  WiFi IP address 192.168.1.6
  WiFi signal strength -66dBm, mode 802.11n, reconnections 0, sleep mode modem
  Clock register 00002002
  Socket states: 4 0 0 0 0 0 0 0

[Pumlux]

@chownki
I had some similar error messages on my Duet 2 Wifi months ago.
All was working fine and suddenly some phases may be disconnected.

To make it short, in my case the connection of the stepper was weak.
I checked it a couple of times and I thought the connections is fine, but when looking in detail, the crimping on the cable was not perfect and I could pull the cable out of the contact shoe.

To be 100% save I soldered the cable to the connector shoe and this error message did not appear again.
So shame on my crimping style.

You may check with a complete new cable on your driver giving the error message.

[Phaedrux]

@chownki said in Phase A and B may be disconnected:

Driver 0 is my X axis and its running fine.

What speed are you moving at when you get the errors?

[Chownki]

@phaedrux
I was running at F12000, used those speeds on my a mk3 with E3D 48mm steppers, guess the orginal prusa steppers dont like those speeds, when i drop to F8000 errors are gone.

Do you know if its because the steppers are missing steps ill get those errors?

[dc42]

@chownki it's because the inductance and back emf of those motors exceeds the power supply voltage at those speeds. When this happens, the motor positioning becomes less accurate, and the motor gets noisier.

If you are using 12V power in your machine then upgrading to 24V will allow higher speeds, although of course this normally requires different the heaters and fans.

Use our motor calculator at https://www.reprapfirmware.org/emf.html to estimate the maximum speed before the supply voltage becomes insufficient.