Re: Looking for technical information online

[mjmahon@aol.com (Michael J. Mahon)]

In article <MPG.18d8abc67cda5f91989937@news.t-online.de>, Michael J. Sch�lke
<mjschuelke@hotmail.com> writes:

>Where can I find hardware information on the Apple II (in its various 
>incarnations -- II+ and IIe would be especially interesting ATM) online? 
>The more technical and the more exhaustive, the better. 

Unfortunately, the really great stuff doesn't appear to be on the web.

Sather's "Understanding the Apple ][" and "Understanding the Apple
//e" are, in my opinion, the definitive works.  One or the other comes
up on eBay every once in a while, and various used booksellers get
copies from time to time.

>Currently, I'm looking mostly for repair related information, as there 
>is a dead II+ sitting on my desk. I've already found the Red Book, and 
>while it contains all the schematics, it doesn't have the circuit theory 
>backing them -- descriptions of how the circuits work, which signals are 
>to be expected at which points, etc. Of course, I could work all of 
>these out on my own, but that takes time -- a lot of time. 

The good news is that you can almost certainly fix it without getting
a deep understanding of its innards.

First, remove any peripheral cards that may be in the slots, except a
memory card in slot 0--no need to make the problem more complicated
than necessary.  Then try it out.

If it doesn't "beep" when you turn it on, then the CPU is not running
far enough in the reset code to do that--it's a good quick test of whether
the II is alive.  If no beep, turn off the power and loosen and re-seat each
of the socketed ICs.  This will correct most problems with oxidized IC
leads & sockets.

Check that memory chips are present in all sockets across the three
rows of memory sockets.  (Actually you can get it to work with just one
or two rows full, starting at the back row, but three is most common.)
It is very common for the memory chip in the back row nearest the
power supply to be missing, because a 16KB card was pulled, and the
chip that belong in that socket was relocated to the card.  If the 16KB
card is present, then there is a 16-pin DIP jumper that goes between
a socket on the card and that socket on the main board.

Then try the power again.  If it's still no-go, get out your multitester
(you need one!)  and measure the voltages at the power supply
connector.  They should all be within +/- 10% of spec (hopefuly
better than that).  Obviously, +5v is critical--if it isn't there, then
nothing can work, and you have a power supply problem.

If the voltages are present, and the chips have been re-seated, then
you have a more "interesting" problem.  ;-)

Why not give this a try (unless you already have) and get back to
us about what happened.

>So, can you help me? The web searches I tried before always drowned me 
>in superficial results.

Of course, even after you get it working, it's still a great idea to learn
more about the design.  Although there are many helpful documents
on the Net, you will probably still want to get the "real stuff".

When perusing the Web, it's helpful to have some good starting
points.  Rubywand's excellent A2 FAQ is a fine place to start, and
it has lots of useful links to other sites:

http://home.swbell.net/rubywand/A2FAQs1START.html

Enjoy!

-michael

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