IIGS-Halts during boot sequence

[Kurt Proegler <kproegler@cas.org>]

I'm looking for assistance (point me to some documentation, offer some 
advice) to get my IIGS up and working again.  After a very brief time 
when it displayed intermittent errors, it is now in a state where on 
startup I get a screen that offers 4 choices: enter control panel, set 
60hz defaults, set 50hz defaults, continue restarting.  I can get to the 
control panel, all looks OK.  If I restart holding down OA, it appears 
to cycle through a test sequence: screen patterns, borders, a scale of 
notes, and ending with a "System Good" message.

Other evidence:
1) During its intermittent error state, I ran the memory checker that 
RamKeeper has and it indicated a bad memory location.
2) I have removed RamKeeper, and an extra memory card.  With only the 
Apple memory extension card, with 512K of allegedly used but good chips, 
the symptoms are as stated above.
3) Various combinations of chips in this card, RamKeeper, and another 
1MB extension card all indicate that the memory is generally getting 
recognized (indicated by Total Free RAM on the control panel).
4) I removed TransWarpGS and replaced the original CPU. no change.
5) With no memory extension card in at all I get the same problem.

Item 1 & 2 seem to point to one of the 8 soldered memory chips on the 
memory extension card being bad. But item 5 raises a question about 
this. Item 4 would seem to indicate the CPU is OK.

I'm tempted to either a) get a used but good memory extension card or b) 
try and replace the soldered chips on my card.  But only if it seems 
fairly certain that the chips are the problem.  

Am I going down the right path?