Fixing a Apple IIc

[tomk@pro-nsdapple.cts.com (Tom Kelly)]

 dempson@actrix.gen.nz wrote:
 The upgraded ROM has a full self test, which should report which RAM
 chips are faulty.  It is then a matter of replacing the chips in
 question.  The self test displays a RAM fault as a series of eight 0 and
 1 digits, with 1s corresponding to the faulty chips.  The leftmost digit
 is bit 7 (RAM chip MRD7), the rightmost bit 0 (RAM chip MRD0).
 
 If an asterisk (star) is also displayed next to the numbers, then the
 fault is in auxiliary RAM, not main RAM.  The auxiliary RAM is labelled
 ARD7 (bit 7) through ARD0 (bit 0).
  =====================================================================
 When I ran the self test I got: RAM 0 1 0 0 0 0 0 0.
 I replaced MRD6
 
 Next I got: *RAM ZP 0 1 0 0 0 0 0 0.
 I replaced ARD6.
 It seems ODD that the same bit would fail in both main and aux memory.
 What does the ZP mean?
 
 Now it seems to pass RAM test, but stops and displays GLU on the screen.
 I presume that means that the chip on logic board labeled GLU is bad.
 It is soldered to the logic board.  Should I cut it out or desolder it?
 I am concerned it may not really be bad. I have never seen it fail before.
 What exactly is it?.
 With the proper programmer, can it be duplicated?
 Apple parts are so hard to find.
 
 I have another IIc that is broken that I can use for parts, but do not
look
 forward to desoldering the "good" part.
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