kdr
Experienced Member
I've successfully used the 5160 schematics to diagnose two different turbo XT clone motherboards, so in my experience they tend to change very little (mainly just various hacks in the vicinity of the 8288 clock generator for the turbo mode).I don't have a schematic for this board. I'm using the IBM 5160 technical reference and it was close enough to follow along
I had a dead 5150 motherboard where the issue was a bad 'LS86 chip (quad XOR) which had an *input pin* internally shorted to GND.... that was a hard one to diagnose!On the 74LS245 between the D bus and XD-bus--it seems the DIR is stuck low. DIR is fed from output 3Y of a 74LS27. Input 3C to the 74LS27 appears to be stuck low, and comes from output Q1 of 74F20.