Re: Apple IIgs random hardware crashing - any ideas?

[ToasterKing <toasterking@SPLATbigfoot.com>]

Okay, as a follow-up to the totally bizarre behaviour of my ROM 3 IIgs
as of late, I've stumbled upon something interesting.  Last night I
completely removed the IIgs motherboard from its case, and reinstalled
the cards and reconnected the cables with it sitting unhoused on my
wooden shelf.  Ever since then, it has worked fine.  I used it for a
few hours last night with SCSI and full acceleration and never had a
problem.  Since then I've left it repeating the built-in hardware
self-test for 24.5 hours, and it hasn't failed once.  (Formerly it
would fail within 15 minutes of repeated tests.)  The funny thing is I
see no way any part of the board could possibly be shorting to the
ground shield in the case -- it has more than enough clearance
everywhere.  I've also tested to be sure that the add-on ports
installed in break-out panels in the rear of the case (connector for
SCSI card, jacks for sound card, hyperstudio sound-sampler add-on card)
and the power supply are not causing ground loops, both by checking
with an ohmmeter and by disconnecting/removing them.  The GS still has
crashing problems only when the board is seated in its case.  (The
board has been removed/reinstalled several times and still this remains
true.)  I've also tried poking/prodding/thumping the board while out of
the case and while performing intense operations to see if I could
invoke a crash, which would indicate I had a cracked trace, cold solder
joint, or other loose connection, but still it refuses to crash outside
of the case.  Also, the video corruption I mentioned while running NFC
Megademo disappears when the GS board is removed from the case.

Now at least I know my board is okay, but this is driving me crazy! 
Does anyone have any bright ideas I neglected to consider??

Many thanks,
TK

Original symptoms below for your reference.

In article <061020030342332489%toasterking@SPLATbigfoot.com>,
ToasterKing <toasterking@SPLATbigfoot.com> wrote:

> I have a ROM 3 Apple IIgs.  Recently, it was stored in a cardboard box
> in a hot attic for about 9 months.  Everything worked well before the
> storage.  After being unpacked and reconnected, I'm having strange
> stability problems.  Sometimes the IIgs runs perfectly with no
> glitches; other times, it crashes every few minutes.  No variables I
> can manipulate seem to change the tendency, but sometimes the symptoms
> magically go away for no discernable reason.  The problems cannot
> always be reproduced, and never occur at a predictable juncture. 
> Examples of what happens:
> 
> o Randomly crashing to the monitor while running GS/OS, an 8-bit
> program, or simply pressing Ctrl-OpenApple-Esc at boot time to display
> CDA menu
> o Occasionally on power-up, a checkerboard pattern on video and no boot
> o Occasionally does not recognize SCSI disks
> o Hangs in GS/OS with mouse pointer freeze, occasionally with minor
> video corruption
> o Crashing to the monitor when launching a GS/OS application, copying a
> file, emptying Trash, etc. or crashes in ProDOS-8 applications at
> random, or when using a system command in BASIC.SYSTEM like "BYE".  A
> keyboard freeze sometimes occurs along with this, though the cursor
> continues to blink.
> o Apple IIgs built-in system test usually completes with "System Good",
> but occasionally fails with code 0B030000 (Interrupt test failure on
> 1/4-second interrupt test) or 093B7200 (ADB failure with checksum
> 3B72).  The probability of failure always varies, even when all other
> environmental variables are kept constant.
> 
> In addition, I've also noticed that when running the Ninjaforce
> Megademo (patched for ROM 3, and with AppleTalk/IRQ delay on TransWarp
> GS disabled as suggested), there is always video corruption on the
> lower 1/3 of the display, even though the program may not crash.  I
> don't experience video corruption in any other programs unless it's The
> symptoms are unaffected by temperature or uptime duration, or by
> certain hardware being connected.
> 
> Things I have tried, which did not help the problem:
> o Removed all cards, including RAM expansion, leaving no external
> connections except ADB and composite video out
> o Used a different keyboard and mouse
> o Turned off nearby electronic equipment that may be causing
> interference
> o Cleaned pins and reseated all socketed ICs on motherboard
> o Checked case for board-to-shield shorts
> o Tried different power supply (already 120 Watts), and with and
> without spike protector
> o Replaced all electrolytic capacitors in power supply
> o Replaced electrolytic filter capacitors on IIgs motherboard
> o Fattened power supply +5v, +12v, and ground leads
> o Fattened power traces on motherboard to slots 3, 5, and 7
> o Leaving case open and using a large box fan as cooling
> o Checking for any hot ICs
> o Disabled TransWarp GS
> o Removed TransWarp GS and swapped in original 2.8 MHz 65816
> o Set System Speed to Normal
> 
> My hardware is set up as follows:
> - ROM 3 (1989 revision, 1 MB) motherboard.
> - 120 Watt power supply.
> - System Saver IIgs on top of the IIgs case
> - TransWarp GS accelerator in Slot 3, modified with v1.8 ROM, 14 MHz
> Sanyo-designed 65816, 32K cache SRAMs, 40 MHz oscillator for 10 MHz
> clock
> - Applied Engineering Sonic Blaster GS card in slot 5
> - Apple High Speed SCSI card in slot 7.  500 MB hard disk, SyQuest
> SQ555 removable cartridge drive, and CD-ROM drive on SCSI bus
> (terminated).
> - Applied Engineering GS-RAM III populated with 2 MB RAM
> - HyperStudio sound digitizer connected to Ensoniq port and fan
> connector
> - Multiple operating systems on hard disk (System 6.0.1, 5.02, 4.0,
> ProDOS 16, ProDOS 8), all used for testing
> - AppleTalk is enabled on Slot 1.
> 
> If anyone has any ideas or suggestions, they would be graciously
> accepted.  Thank you for reading!

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