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.