A Poor Man's PLCC Probe

Experimenting with an old Macintosh Classic, I searched for a way to easily connect my logic analyzer to its 68000 processor.

The MC68000 in the Macintosh Classic is a surface mounted 68-pin PLCC package, of course it’s possible to attach many SMD grabbers to the pins of this package, but that is far from practical.

True PLCC test adapters are far too expensive for hobbyist purposes, so I tried something else, with good results. On Ebay, I ordered a few PLCC86 sockets, and tried to placed one on top of the MC68000. This works, but not reliably, as the contact springs of the socket force the socket off the IC package.
By sanding down the PLCC socket and removing four internal notches, the socket can be pushed farther over the IC and you get a pretty snug fit.

Spot the differences in the pictures below, left the original socket, right the modified one.

The modified socket attaches tightly around the PLCC IC to be probed, tight enough that it takes some force to remove it again. Certainly good enough for probing, but it may even suffice for adding hardware permanently to the machine.

Below you can see the socket mounted on top of the MC68000 on a Macintosh Classic logic board.

Once mounted on the board, it’s easy to attach logic analyzer pods to the socket pins. But as you can see in the last picture, this becomes a ratsnest pretty fast. It suffices for now, but terminating the logic analyzer to an adapter PCB with proper header connectors for this purpose will be the next step.

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