diff --git a/ohmpi/hardware_system.py b/ohmpi/hardware_system.py
index 51a8440e3b7326202aff87066ec7e25fb7c9c47b..6eb7a3678254e2760101fc7d20685bf6936de820 100644
--- a/ohmpi/hardware_system.py
+++ b/ohmpi/hardware_system.py
@@ -398,9 +398,8 @@ class OhmPiHardware:
         """
 
         if self.tx.pwr.voltage_adjustable:
-            print(f'Vmn max: {vmn_max}')
             if vmn_max is None:
-                vmn_max == self.rx._voltage_max / 1000.
+                vmn_max = self.rx._voltage_max / 1000.
             print(f'Vmn max: {vmn_max}')
             if p_max is None:
                 p_max = vab_max * iab_max