I grabbed a used PLZ-603W off of eBay last week, and I'm in the middle of doing some general testing / cleanup / teardown. Thus far, the load seems to work OK in constant current mode up to about 300 watts or so, but I've discovered a strange set of issues and would like an expert opinion if possible.
For those who are unfamiliar, this load takes up to 3 internal load modules, each of which seems to bear around 300W. For this 600W unit, there are two modules installed, a master and a slave module.
Firstly, the master module's fan does not spin up at all. I've verified that the fan itself is working fine, and I know that the slave module's fan runs continuously during operation, so this seems wrong.
Secondly, suspecting a fault with the master load module, I completely disconnected the slave module and ran the load with only the master module. With this setup, the load still boots normally and reports no errors, and the module's fan still does not spin up. However, the load behaves strangely when operating with only this module: in constant current mode, the load will set and sense the nominally specified current, but the actual current draw is only half that value. I'm not sure whether that is by design or the symptom of a fault, so I would appreciate any insight on the matter.
Thanks in advance!