Hi, Rescued an Apple clone from the trash yesterday (Ci Base48) - appears to be all there, but power supply is dead. I've had a bit of experience with small DC transformerless switchers, but not with mains power, transformer based switchers like this. Fuse was blown - replace, powered up through a 60w light bulb, the lamp comes on (and stays on) at full intensity - clearly excessive draw. Board bears the name "Seasonic". I have no schematics. - Mains power goes to full-wave bridge rectifier and filter caps to produce HV DC supply. - HV DC supply goes through fuse to a single heat-sinked power transistor (C2979) which drives the transformer primary. - Secondaries from transformer are recitied by big heat-sinked diodes, then filtered, and monitored by a circuit, which feeds back through an opto- isolator to the control circuit for the power transistor driving the primary (presumably this is the method of voltage regulation). Opservations: (Powering unit through isolation transformar, variac and 60w light bulb) - With fuse removed, HV DC supply apears to work fine. Filter caps charge up to in the high 100's Volts. - No light from lamp indicating very little drain (as expected). - With fuse installed, lamp lights at full intensity. No voltage measured across HV filter caps at all. - Power transistor does not appear shorted - Removed from circuit and using a diode test function, it shows two normal semiconductor junctions. Can anyone offer suggestions on where to look next? Are there any common failure modes of this type of power supply design? Regards, Dave -- dave04a (at) Dave Dunfield dunfield (dot) Firmware development services & tools: www.dunfield.com com Vintage computing equipment collector. http://www.parse.com/~ddunfield/museum/index.html