When the PR-4000 is used with the regulated PS-4000 switch mode power supply, a condition can exist where there will not be enough output from the PS-4000 to satisfy the 24 vdc regululator in the PR-4000. Further, when these two units are working together, there is no need for the VR in the PR-4000 as the PS-4000 has a regulated output. It is recommended when these two units work together that the 24V regulator on board the PR-4000 be bypassed.
 

The 15vdc and 24vdc regulators are seen below (left to right)
Notice the bypass strap installed on the 24vdc VR

This photo shows the strap in closeup.
Note that these regulators are the same adjustable type