Since you've taken my name in vaio, I'd better reply :-). However, I've never been inside a TU81+ (or a TU81 for that matter), so this is going to be somewhat general. I am going to assume ti's a switch-mode PSU and that it's somewhat separate from the rest of the machine. In which case I'd start by indentifying the output connections (it should be fairly easy to find at least the ground and +5V lines, maybe +/-12V as well). I'd then check those with a voltemter with the thing powered up -- with SMPSUs if one output is there and correct, generally the others are OK too, so you don't need to check all of them, at least not at this stage. Assuming the PSU is dead, I'd then disconnect the outputs and put dummy loads (car bulbs, for example) on the main outputs. If it works then, you've got some short or other overlaod in the rest of the machine. I think this is unlikely, since that normally causes the PSU to 'tweet' as it starts up and shuts down repeatedly. OK, now we know there's a real PSU problem. Pull the plug, and check the voltage across the mains smoothinc capacitors (these will be large-ish electrolytics, around 200V rating). If the chopper isn't running but there are no other problems, it's not unheard-of for these to remain charged, and they _will_ throw you across the room, even with the thing unplugged. However, if they are charged, then it means that the mains input circuit is working. Most likely the input circuit, in 110V mode, is a voltage doubler using the 2 caps in series and 2 diodes from a bridge rectifier (either 4 discrete diodes or a bridge rectifier module). You should be able to indentify the +ve and -ve ouputs of this circuit. Clip a voltmeter across these points (don't hand-hold the probes, you are working with rectified live mains which _will_ kill you) and power up. You're looking for about 350V DC here. If that's working, unplug again, and let things discharge. Now identify the chopper transistor (a power transistor or mosfet on the mains side of the PSU) and test it. Maybe it's open (unlikely). Then look for a resistor of a few hundred k ohms (or a couple in series) choppper control circuit. Check it. THis is the startup resistor and often causes the problem you're having. If it's open, replace it with a resistor that will stand a few hundred volts (many small resistors won't, take care). Then come back here and let us (me?) know what you've found. -tony