JUMO 709040 TYA-110 thyristor power unit Operating Manual - Manual (Page 39)

Power units 02.06 39
6 Settings
6.1 Opening the housing
It is easier if these adjustments are carried out before the unit is installed.
h Use a screwdriver to lever the spring fixing lug outwards.
On the 150 A and 250 A versions: press both spring lugs inwards.
h Pull off the cover from the front.
V Adjustments must only be made while the unit is disconnected
from the supply power!