[cctalk] Re: Repairing an Olivetti M24 PSU

Many switching supplies have VERY tricky startup circuits that tickle the controller to start and then power the controller from an auxiliary winding on the transformer. Some of these circuits might require some capacitor to fully drain before they can start properly again. Some of these circuits may have a really high resistance value that charges the controller's supply cap, and then a transistor turns off that path when the controller is running to avoid overheating that resistor. These circuits will be at mains potential so be careful when testing them.