Re: Apple IIe Crashes into Monitor

[Kevin Dady <kevin@hackaday.com>]

On Apr 9, 7:10 pm, dog_...@macgui.com (D Finnigan) wrote:
> For a few months now, my standard (unenhanced) Apple IIe has been having
> stability problems, usually manifested by system freezes, crashes into the
> monitor, disk motors being engaged (sometimes both at the same time) when
> they shouldn't, and garbage characters appearing all over the 80-columns
> screen.
>
> I'm running a full system with a RamWorks III with 256 KB, SSC, Transwarp,
> Mouse interface, Disk II controller, and Apple 5.25" controller.
>
> I had suspicion that that the Transwarp was causing problems. However, it
> seems that if the underlying system is unstable, the Transwarp won't mask
> those problems.
>
> The IIe will crash into the Monitor even with *no cards* installed in any of
> the slots.
>
> Here is the scenario from last evening:
>
> The IIe had been running on and off for about an hour. I noticed that it was
> having problems, so I switched it off and removed every card from every
> slot.
>
> I turned it back on, then hit Return a few times. I typed in a 2-line BASIC
> program that printed two words on the screen. I typed RUN. The program
> executed, and I waited at the BASIC prompt for about 20 seconds.
>
> The IIe then proceeded to crash into the Monitor twice in rapid succession,
> with two beeps spaced less than a second apart:
>
> FC26 - A=5E X=0D Y=00 P=37 S=E7
> *#
> FC26- A=0D X=16 Y=4D P=37 S=DC
> *
>
> (hash mark # represents the cursor)
>
> About 30 to 45 seconds later, there was another beep and crash:
>
> 3F6B- A=70 X=A0 Y=AF P=FC S=FB
> *
>
> It is my understanding that crashes like these are caused by a BRK ($00)
> instruction being encountered. However, upon examining memory two locations
> back from the reported location, I could find no BRK instructions.
>
> My conclusion then, is that something is wrong with the 64k motherboard
> DRAM.
>
> Scenarios just like this, where the Apple IIe crashes into the monitor while
> waiting at the BASIC prompt, have happened at least 3-4 times in the past
> few months. The Apple runs fine more often than not, however.
>
> I have run the Apple System Diagnostics for IIe (the one that has the
> AppleWorks-like interface) several times in the past month, but it does not
> report any problems, nor does the built-in IIe self-test report an issue
> with the RAM.
>
> Therefore, it seems like the problem is either:
> a.) intermittent (fun...)
> OR
> b.) resulting from some other component
>
> I was measuring the +5 and +12 voltages to see if they were within range.
> They were. However, when measuring the +5v across one of the 64kx1 DRAM ICs,
> I accidentally made a short across two of the pins. This short caused the
> IIe to crash into the Monitor with a beep, as well as several garbage
> characters to appear all over the screen.
>
> I wonder if there is a short in one of the DRAMs, or maybe this is just a
> coincidence.
>
> As for the other problems mentioned earlier, the disk motors being randomly
> engaged and the garbage characters on the 80-cols screen, I have not begun
> to investigate the causes yet. One thing at a time, I think.
>
> --
> ]DF$
> Mac GUI Vault - A source for retro Apple II and
> Macintosh computing.http://macgui.com/vault/

too bad you dont have a scope to see whats going on, but as a wild
stab there is something oscillating on your power, do you have another
power supply to try out?