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Unusual IIc??


   I have 2 IIcs (both 255 versions) but one has some modification done 
to the original motherboard.

   On one of them, R6, R11, R21 and R22 as well as R13, R14, R12, R15 
have a resistor of sorts soldered on them. 

   Next to the resistors(?) are two chips, one labelled L M311 M8416 A+ LM 
311N and the other labelled 406 A NE555P.

   Why would 2 identical 255 IIcs have a variance from one to another?  
One was assembled in the US and the modified one in Ireland.  Both have 
128K and neither support a memory card or UniDisk 3.5.

   What do these extras circuits and chips do?

Thanks,

Tony