Re: 1977 original apple II restoration (continued)...

["Ralph Hyre" <rwhyre@gmail.com>]

I don't know if I agree with this plan - replacing one chip at
a time is a better approach.

>Then take 5-10 parts at a time from your II board --
>starting with the ROMs -- and transplant those into the working board
>-- testing each time with a power on to be sure that the transplanted
>parts are working correctly.

I once loaned my disk ][ card to a fellow Apple ][ user in my dorm.
He was building hardware, and when I got the controller back I noticed
my system wasn't booting anymore.

He fried a 7405 on the Disk ][ card, which was pulling RST low
on the 6502, and never letting go.  I used a logic probe, but not for
very long before the problem was obvious.  My hazy recollection is
that RST was run to the keyboard encoder board, so there were very
large pins.

I was able to troubleshoot by noticing the machine, and diagnose the
blown chip.  (Imaging trying to do chip-level repair today!)

Anyway, I replaced the blown chip, and was going again.

The oldest schematics I have are from the Apple ][+, not the ][.

As I recall, you had to manually push the 'Reset' button to get the
original
Apple ][ going, since they didn't have autostart ROMs or other more
modern
conveniences.

If you have a  low enough serial number, your keyboard will have N-key
rollover,
which is a think of beauty compared to the 2-key rollover on the ][+
and later models.

Have fun,

- Ralph Hyre