Techniques are disclosed for assessing the conditions of LEDs and power supplies of solid state lighting systems. The techniques can be used, for example, to measure the capacitance of an output capacitor C in a switch-mode power supply (SMPS), and to measure the condition of the LEDs being driven by that power supply. In some cases, this assessment can be implemented in a lighting controller that controls the lighting system, which may be configured to simultaneously determine C and the conditions of LEDs. In one example case, the techniques can be implemented, for instance, in a micro-controller operating the lighting system. A lighting system implementing the techniques can be periodically assessed so as to provide real-time diagnostic capability. Numerous example embodiments of SMPS LED lighting systems will be apparent in light of this disclosure.