# Specific 3D Printers, Scanners, & Hardware > Other 3D Printers / Scanners / Hardware >  Anycubic Upgraded driver issue - TMC2208

## Thesavo

On my Anycubic Mega S, I just replaced the green mask a4988 drivers with BigTreeTech 2208 v3. I left the firmware as-is and rotated the motor connectors 180 degrees as recommended in the Youtube Video by "Chris's Basement".
I set all the vRef's on the test point to 0.800v, near the Enable Pin.   I tried printing a benchy and I appear to have an issue.   It seems to me the Z axis is not moving up during the print.  However when I home the printer or manually move the print head with the LCD or octoprint, it moves just fine.  Am I  safe to bump the VRef?   It is rather arduous to do in iteration as it requires removing the bottom cover each time and re attaching.  As the Stepper motors have no branding other than XY, it is hard to find a spec sheet.

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