Paris Rhone later type ZT2130A regulator

Adjustment of the earlier Paris Rhone regulators (ZT 3115A and ZT 3118A) involved the use of feeler gauges to set the gaps correctly followed by physically bending the tensioner plate to achieve the correct voltage / current settings. The later ZT3120A is much easier to adjust once the gaps have been checked as the tensioning plate includes a nut to adjust the tension and hence voltage or current setting.

Unlike the earlier models which were painted black, the factory finish for the ZT3120A appears to have been changed to green ( I have yet to come across a black one). The example shown above was reconditioned by ERGM at Bruz in 1987. Interestingly, only the points assemblies on the voltage regulator coil were actually renewed (note how clean and shiny the metal is compared with the others). Points, particularly on the voltage regulator coil, tend to be the week point of the Paris Rhone design which, unlike the Marchal regulator, contain no condenser or free wheeling diode to reduce sparking. The points become badly pitted and worn making the regulation go haywire and impossible to adjust reliably even if cleaned up. Typical wear is shown in the photo below and it is common for at least one hole to appear though two have burnt into the example on the right.

When a Paris Rhone regulator has reached this point it is basically unserviceable.