Failture modes of SCR controllers or SCR power regulators.

Failture modes of SCR controllers or SCR power regulators. The main parts are simply the PCB and the SCR modules which they trigger

The only recommendation to offer is that the SCR modules and the heating elements need to be cleaned regularly (suggest annually) in case of any carbon build up which in the cooler months will get damp and cause arcing. 

By far the 4 most common reasons for failure are 

1) PCB is too old. 15-30 years can have failing parts and uneconomical to repair

2) SCR modules are worn out. typically changed around 10 years, or less if under high stress from highly inductive loads. 

3) Over Temperature / Inadequate Ventilation or fan failure. (normally therm overload will protect unless it it also burnt out due to overuse. Mostly in summer months

4) Carbon build up in heating elements and/or SCR module. Due to no routine cleaning of the controller. Usually in cooler months due to damp carbon tracking and shorting.