[ajgriff]

Nothing wrong with the approach being described and in the end it will of course be down to Colin to decide how he wants to proceed. I just think there are some advantages to an alternative approach as follows:

1. Acquire eight 4116s from the eBay seller or Refugee.

2. Remove all sixteen 4108s.

3. Fit sockets to the eight RAM positions in row I.

4. Reconfigure the jumpers.

7. Insert the eight 4116s into the sockets.

6. Switch on and say a prayer (if applicable).

This would eliminate faulty system RAMs from the equation. If the PET still refuses to say READY and flash its cursor the PIAs would be my next port of call. These are easy to test assuming they're socketed. Just remove them both and if one's faulty the PET will say READY without flashing a cursor. The faulty chip can then be identified by refitting them one at a time.

Alan