I reckon the use of those 'MOV's in the Decca is a bit belt-and-braces
anyway because both output ports are diode clamped to positive and
negative rails. Maybe they are faster than the diodes and protect
against fast spikes.

Cheers, Tom G3OLB

G0MRF wrote:

It should be possible to determine the voltage rating of the MOV from the manufacturers part number in the Decca manual. If the original part is not available I wonder if its possible to remove a working unit from one of the other modules and measure its capacitance and compare the value against a potential replacement. Hopefully minor differencies would not be critical as the MOV is in part of the circuit operating in class D and there should be sufficient drive to mask small changes in capacitance.