Re: Help reviving II+

[Robert Jensen <jensen@aplcomm.jhuapl.edu>]

In article <2t90li$5nv@maxwell5.ee> Dan P. Scholnik, dpscholn@mtu.edu
writes:
>	A friend and I were working on an interfacing project for my II+
>(48K ram, 16K ram card, 2 disk drives, dos 3.3), and while I was not
present,
>he removed the card while the power was on. Now, of course, when it is
turned
>on, nothing happens. What I need to know, is what blew? THere are a lot
of
>chips on the board, and I don't want to test them all manually. I pulled
>the roms and built a tester with my PC parallel port, and they're ok.
Does
>anybody have any experience with this?

I built several cards for my II+ and managed to damage things twice by
pulling
a card when the power was on.  There was a lot of turning on, turning off,
inserting, pulling, and testing.  Things got out of phase.

Once, I killed a chip in the timing section.  The result was to pull down
the +5 supply so there were no signs of life.  I don't know how the repair
guys tracked it down.  If the chips were pulled in groups I suppose that
the
one excessively loading the power line could have been localized.

The second time I killed the processor.  Everything was present (+5, clock
signals, etc) except no processor life.  The SYNC pin (7) is a good test
of
life.  I replaced the processor and away I went.  I verified address
decoding
by hand (pulling address lines up and down) before replacing the processor
just to convince myself that I was ordering a part that would fix the
problem.

I would look for +5, look for clock signals, and see if the processor is
trying to read the reset vector after a reset.  I assume that you tried to
power up with no cards present, just to check that the problem is on the
mother board.

Good luck.  My Apple II+ is still alive and useful after 15 years.
=========================================================
Bob Jensen
bob_jensen@jhuapl.edu