IIe hardware problem

[snelson@blue.weeg.uiowa.edu (Steven Nelson)]

Can anyone offer some diagnostic insight?

After 10 years of faithful, continual service (ie, I rarely power down),
my IIe enhanced (upgrade) suddenly got very sick.  It will crash at
unpredictable times of a few seconds to several hours between crashes.
Self-test will be either System OK, or RAM  0 0 0 1 1 0 1 0 .  Except,
the RAM bits will never be same,  one time RAM  0 1 1 1 1 1 1 1, and
maybe RAM  1 0 0 1 0 1 1 0 the next time.  No pattern of 0 and 1 I can
discern.  I think it is motherboard ram as there is no * after RAM
(ie, RAM*), or whatever I believe indicates AUXRAM.  Diagnostic software
never reveals problems but will eventually just crash.  (I ran memory tests
for several hours one night before the IIe just froze/stopped.)

The only 'repair' I've tried is the standard: pull and reseat all inter-
face cards, push down all IC chips, rotate/swap RAM chips, replace 
power supply with a spare one.  & my #1 fix-all: blow at all the dust :)
Nothing has helped.

Diagnostics are a little hampered by the hardware I have:
  Auxmem: 1 Meg RamWorks III
  Slot 1: Super Serial card/Imagewriter
  Slot 2: Super Serial card/(modem setup)
  Slot 3:
  Slot 4:
  Slot 5: Unidisk 3.5 controller/2 drives
  Slot 6: Duodisk 5.25 controller/drives
  Slot 7: Appletalk (Workstation) card
          8MHz Zip chip
          No-slot clock under CD-Rom chip

lots to go wrong :)  The Vulcan 40 drive/powersupply died a couple
months ago, leaving slot 4 open :(  A Kensington system saver fan has
always been with the system.

Zip and Ramworks diagnostics run fine until the machine stops, so I
never learn much.  My motherboard tests are from an Apple C dealer
diagnostics disk (3.5" /A2T )

Where should I start trying to revitalize this trusty old friend?
Thanks for any help.  Email or followups are fine.

  --Steve  (steven-nelson@uiowa.edu)