68000 Pod Query

I have a broken pinball motherboard here that I'm trying to fix. I'm using a
Fluke to spy on the data bus because it has a line stuck high.

Connected to the data bus there appears to be:
1 EPROM
1 RAM
1 Resistor pack
A couple of 74HC244's bringing in the switches matrix data
A load of 74AC374's driving the transistor-controlled outputs

I've isolated the EPROM, RAM and 244's from the circuit and it makes no
difference.

I don't really fancy removing all the 374's so I thought I'd ask if anyone
knows whether the 374 IC would ever fail in a state where it would drive a
bus line high from an input to that IC? I could understand an output from a
244 doing it but they have all been isolated.

Do resistor packs die very often?

Is there a better way of testing for a stuck bit other than snipping the
pins of the ICs :-(

The processor on the PCB is a 68000 and when I use the Fluke and 68000 pod
to check the bus, it says it's OK, but every manual read from the databus
gives a stuck bit. Has anyone ever seen the 68000 pod do this?

TIA!
Phillip Eaton

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Received on Sat Jun 5 16:20:34 2004