I have one P6 power supply here that is fine with no load or partial load but blows a fuse under full load. With all other boards unplugged from it, the +5, –5, +15, –15 seem okay. With three boards powered up, it still looks okay. As soon as I plug in the power cable to the 366 board, one of the fuses starts to light up and will blow in a couple of seconds. All voltages start to drop as the fuse lights up. I tried another 366 board with the same result. The 366 board seems to be very power-hungry. I tried pulling out the pin for +5D from the connector (it has separate +5 volt wire for analog and digital busses) and plugging the 366 back in. Everything else powers up okay with that one wire disconnected. So, the +5 seems to be the problem. Before I start replacing transistors on the power supply I was wondering if anybody else has a better idea of how to narrow down the problem. I have a good KLM-376 power board and the bad one. I haven’t unsoldered any parts to test them in isolation, but everything I’ve checked in-circuit measures the same on the good and bad boards. It think this would be easier to debug if something would just fail completely, rather than working okay up to a certain point. Where is all that current going?
Thanks,
Don B.