Fortunately, these chips are easy to replace, At least, they are on the A500 and A2000.
Not so easy to replace on an A4000 - they're surface mount. :-( (Also, not worth the advice of swapping them. IF you're going to attempt any repair, might just as well replace 'em with known good or NOS - several places still sell 'em.)
The PARNET cable should work fine between the A1200 and A4000. Though, unfortunatly, there are a LOT of shoddy PARNET cables out there. (The plans were freely available as a fairly simple DIY project, and lots of poor-soldering hobbiests made them back in the day...) If your PARNET shorted internally (or if someone made the modifications to make it work with the A1000 parallel port?), it could have shorted and taken your CIA chip with it.
