Nice that you didn’t need the printed input ratings to identify the voltage selection feature. I see that you were tipped off by the wires pouring out of the transformer. If this unit did NOT feature the auto-voltage selector, what would I be seeing instead? Just two wires and a ground?That photo of the input rating confirms that the amp has automatic mains voltage selection – my theory of the voltage selection relay switching, as being the fault is looking good, but precisely what is causing it is another issue.