First post, by GabrielKnight123
I've been testing motherboard ISA pin voltages for 16 bit ISA on a motherboard that the serial port for the mouse has stopped working, I've compared the problem board with another board and I'm getting different results that makes it seem the serial stopped working because of too low voltage from a bad capacitor or two. My test rig consists of an IDE hard drive for a load with a good quality ATX to AT power adapter that supplies minus 5 volts, no CPU or ram or anything else and the power supply is a Corsair RM550x. For example on pins A14 to A29 the problem board is out putting between 0.020 volts to 0.016 volts and on the presumably good board its 5.01 or 5.02 volts. Can someone show me a link with the normal 16 bit ISA voltage out puts when testing with no CPU, ram, just a hard drive. Both motherboards are socket 3. I didn't research what the max wattage for a power supply should be when using an ATX to AT adapter with an Intel 486DX2 overdrive 66MHz before buying the power supply but is the Corsair RM550x to much (550 watts?).
Problem board is a GA-5486AL Rev 2A (ALI chipset)
Presumed good board is a VL/I-486SV2GX4 Rev 2.0 (SIS chipset)
The power supply when I test it from the P8 and P9 pins connected to the motherboard is:
+5 volts = 5.02 V
-5 volts = -5.10 V
+12 volts = 12.15 V
-12 volts = -12.22 V
Grey wire = 4.95 V
GND = 0.0