Hallo Ian and others,
I have no experience with a C= harddisk at all but enough experiences in
repairing 6502 based systems. The first question is: is there a schematic
available at all???
If there isn't, then one thing that you, Ian, can do is making one by
re-engeneering the boards you have. Drawing one by hand is enough as I'm
willing to convert it using a schematic-program.
Without a SCH you still can do a lot. At
http://home.hccnet.nl/g.baltissen/debugger.htm you find a debugger (SCH is
missing for the moment). The core of the design is a flipflop that enables
you to step the processor. This little gadget alone enables you to see if
the 6502 does a proper reset. If it does the addressbus must show $FFFC plus
a byte on the addressbus. You need a multimeter to read the individual bits
from the databus. Step the 6502 and read the next byte.
The two read bytes nust give a valid address. If you read $FFFF for example,
the ROM never has been accessed and you know that something is wrong with
the addressdecoder.
About the cut wires: find out what they connected. This info alone could
give you a clue. If it is a clocksignal, address- or dataline, you can
suspect sabotage. In other cases you simply need the SCH.
___
/ __|__
/ / |_/ Groetjes, Ruud
\ \__|_\
\___| http://Ruud.C64.org
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