[ IBM 5150 with IBM 63 watt power supply. ]



So:
* The power supply's fan turns when only the Tandon full-height floppy drive is attached, and
* The power supply's fan does not turn when only the motherboard P9 (+/- 5 volts) connector is attached.

Both of those loads are known to be sufficient on their own to operate the IBM 63 watt power supply in a 5150.


CONCLUSION:  The 5150 motherboard has a short-ciruit in either the +5 or -5 volt lines.


What Now?

What we'll do now is some resistance measurements in order to determine whether it is the +5 volt line that has a short, or whether it is the -5 volt line that has the short.
Click here to continue.