Re: Apple III ram problems

[Rubywand <rubywand@swbell.net>]

Stefan Miganowicz writes ...
> 
> I was working fooling around with my Apple III.  It was working a couple of
> years ago, but the keyboard doesn't work.  I just got another Apple III for
> parts, and I took out the keyboard and put onto the one that worked before.
> Now it says Diagnostic RAM when I start it.  I swapped out the RAM card that
> was connected on the motherboard, and put another one.  It still said the
> same thing, so I think a chip is gone on the motherboard.  Before I swap
> every chip out to find the bad one(I have another motherboard with corrosion
> on it),

     The Apple III-- at least the early releases-- was famous for having chips
pop out of their sockets. Whether or not your Apple III is one of these, after
so many years, it's a good idea to assume that some socketed IC's have pins
which are not making good contact.

     Try scootching up and re-socketing each IC-- this should wipe off corrosion
and reestablish good pin contacts. If you find any gross corrosion-- like the
pins are black-- you should probably wipe the pins with fine sandpaper to remove
the black coating. (Do this in a low static environment.)  An alternative
recommended by George Rentovich is soaking the IC's in a shot glass of Tarnex.

     Before removing any IC, it is helpful to mark the IC and its socket with a
dab of whiteout. This helps to prevent re-inserting the IC backwards.



> could someone tell me what chips are the RAM chips on the
> motherboard.  And a wierd pattern comes up and the manual says it is
> supposed to tell the bad chip, but all it looks like is a test screen.
 ....

     Don't know anything about the Apple III motherboard layout. Any RAM is
likely to be a set of 8-32 same-numbered IC's in rows of 8. When viewing a
diagnostic screen which is supposed to indicate "bad RAM", look for any markers
which indicate position on an 8x4 (8x1, etc.) grid.

     One place you may be able to get helpful Apple III info is Washington Apple
Pi. Their URL is http://www.wap.org/info/ .  Good luck with getting your 'III
going!



Rubywand