Re: Apple II (rev1) instability...HELP!

[Nama <forums6000@mac.com>]

On Apr 8, 3:52 am, mwillegal <m...@willegal.net> wrote:
> On Apr 7, 10:33 am, Nama <forums6...@mac.com> wrote:
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> > On Apr 7, 2:57 pm, Nama <forums6...@mac.com> wrote:
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> > > Hi all,
> > > Me again.
> > > I've recently sold one of my Apple II, and I am moving all my cards
> > > over to another rev1 Apple II that I own.
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> > > I'm trying to find out why this system works fine 90% of the time,
> > > while the other 10% it crashes and hangs or just displays odd
> > > behavior.
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> > > Setup is as follows and is identical to my previous machine:
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> > > 0 - Ram card
> > > 1 - CFFA #2 ( (prodos 1.1.1 / contiki))
> > > 2 - SSC
> > > 3 - empty
> > > 4 - Uthernet
> > > 5 - Echo 2
> > > 6 - Floppy I/O
> > > 7 - CFFA #1 (turnkey startup to DOSmaster 1.7)
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> > > Of course I have tried the system with minimal cards and it still
> > > exhibits weirdness.
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> > > Symptoms:
> > > -Sometimes hangs on boot.
> > > -Strange inverted period often seen in top left corner when booting
> > > from CFFA #1
> > > -Sometimes craches to the monitor
> > > -Doing a IN#1 to launch the CFFA #2 always hangs with a strange
> > > flashing inverted period in the top left corner. often with corrupted
> > > type on the prodos launch screen.
> > > -Once it up and running it's usually fairly stable unless I reboot.
> > > -Have run a looping game for many hours with no problem, but crashed
> > > to monitor as soon as I restart.
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> > > What I have done:
> > > Tried a new set of ROMs
> > > Run Apple test utils on the RAM and ROM...no problems found.
> > > Run the machine from a known good IIe power supply.
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> > > If anyone here can shed some light on my problems, I would be very
> > > grateful. I'm hoping the inverted period may be a good clue to whats
> > > happening.
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> > > I've uploaded some bad photos here if this helps at all:
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> > >http://web.me.com/lord_philip/apple_1_%26_II/rev1.html
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> > > Much thanks in advance.
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> > > Phil
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> > I love replying to myself...there is some satisfaction in knowing that
> > you solved a problem.
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> > THE FIX (as far as I can tell) ...Replace faulty 74LS138 @ H12
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> > From my symptoms I figured there was something up with the slots. With
> > nothing in any of the slots the machine seemed to run ok with no
> > crashes on power up. So I decided to shotgun replace the IC's that
> > were closes to the slots and seemed to have something to do with them.
> > Within 15 mins I had found the culprit.
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> > Can anyone enlighten me as to what  74LS138 @ H12 does? In the
> > schematic is says I/O selects, but I'm not sure what exactly that is.
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> > Phil
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> A few days ago, t posted scans of Apple's hobbyboard doc on my blog.
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> http://www.willegal.net/blog/?p=1447
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>  There is a separate I/O select for each slot, except 0.   It is often
> used
> to select the last 256 bytes of each peripheral card's ROM.
>
> Regards,
> Mike Willegal

Mike, thanks again for the reply.

Just a quick update: Seems I haven't fixed all the issues yet. There
seems to be a heat related issue somewhere. Upon a cold restart (after
the machine has been off for some time), the computer will crash into
monitor right after displaying the 'APPLE ][' text. successive
restarts seems to allow the boot process to get a little further. If i
leave the machine on for a minute or so, the next reboot will work
fine and from that point on the machine seems good.

This issue maybe a little trickier to find, but for some reason I
suspect RAM, don't ask me why, it's just a gut feeling.

Phil