Re: Apple IIe (European/PAL) recovery

[Michael J. Mahon <mjmahon@aol.com>]

David Schmidt <schmidtd@my-deja.com> wrote:
> On 4/17/2013 11:17 AM, barrym95838 wrote:
>>> http://www.willegal.net/appleii/appleii-repair.htm
>> 
>> Nice link, schmidtd; that's just the kind of thing that I was starting
>> to look for, to help Danilo get his Apple out of its coma!
> 
> I'm currently going through the same thing with two comatose boards: they
> are US rev 3 and rev7 boards.  I'm working on the rev 3 now.  Since I
> have no digital tools, I am down to thinking and swapping.  So far I have
> done full-board chip swaps with a known-good rev 3 board (one row at a
> time, including CPU), and I replaced all 3904 transistors.  I
> consistently get a typical memory pattern display on power-up, so at this
> point I'm still suspecting lack of reset-ability.  (The keyboard reset
> key does not in fact reset it.)

Actually, checking for a functional reset is near the top of the list for a
non-functioning processor. 

And an open 0.1uF bypass capacitor can incapacitate :-) a processor. I had
a machine that wouldn't beep until the (subtly) broken decoupling cap
adjacent to the processor was replaced. (It had one lead almost invisibly
cracked as a result of several Zip Chip insertions and removals.)

-michael - NadaNet 3.1 and AppleCrate II: http://home.comcast.net/~mjmahon