[net.micro] Apple II hardware problems

vax2:sota (12/14/82)

I have been experiencing some hardware problems with my original Apple ][
computer, (Rev 0 pcb.)  These problems are always disk related and vary from
total system crashes during disk accesses to frequent disk booting problems.  I
suspect power and ground spikes from the disk are upsetting the system.

I recall hearing that APPLE improved both the power and ground system and the
timing margins of their product several years ago, as they went from Rev 0 to
Rev 7 pcb's, culminating in the ][ plus.  Apple documentation is singularly
uninformative on the subject, and discusses only the substitution of the
autostart ROM for the original monitor ROM.

The only suggestion that I have received to date, was to replace the 3 8T97 hex
drivers (connecting the Address and Data buses to the peripheral slots) with
74LS363 parts.  The LS parts apparently show less tri-state leakage than the
8T's, although why this parameter should be significant is not obvious.
This mod did, however, appear to make a significant improvement in reducing
system crashes during disk accesses.

If anyone is familiar with other mod`s that were made to the original ][ to
improve reliability, I would appreciate hearing about them.  I will summarize
to the net responses made to me if there is sufficient interest.

			Thanks, in advance

jwb (12/16/82)

Be sure you don't have an overloaded power supply as this seems (to me at
least) the most common cause of most of these types of problems.  The Apple
power supply is marginal at best if you have more than a few accessory cards.