Switch mode PA Amp PSU fault

[dennishoy]

I forgot to mention that some untis have fusible resistors which have caught me out in the past. These were colour coded as ordinary resistors, so I replaced them as such only to find out later (when I had the circuit) that they were safety devices. These were low value items, highest was 4.7 Ohms, lowest was 1 Ohm.
Don't get caught out if you find an O/C 'resistor'; it may not be quite what you thought.