Reconstructing an auctioned Lisa

[sigma7]

I'm not having much success.

In IMG_4248.jpeg, it looks like the orange wire on the bottom is connecting pin 7 and pin 11... which would be incorrect.

If jumpers on the bottom aren't working on the top, check that the chip is making good contact in the socket. In particular, a leg may be folded under the chip instead of going into the socket.

Beware that a trace that looks intact may be disconnected from the other side because the plating inside a hole was damaged during desoldering.

[berskyboy]

not getting checkers anymore, but it booted briefly and gave

00000186  0000 0000 FF00 FF00 0000 0000 0000 0000

and then put the good known RAM in slot 1, back RAM slot 2 is goes back to checkers.

YouTube:

https://www.youtube.com/shorts/2qkkvo3cwkU

[sigma7]

In your video, you check continuity for pins 1-8 to the chip on that side (column 7), and for pins 9-16 to the chip on the other side (column 9).

There could be a broken trace still, separating column 9 from column 7. So check there is the same continuity between those chips, or check each pin of the replacement to the chips on both sides (not just the closer side).

Similarly, the traces that go to the chip "below" (pins 2 & 14), may not continue to the chip above, so check these pins connect to both the chip below and the chip above.

[berskyboy]

Hi

In your video, you check continuity for pins 1-8 to the chip on that side (column 7), and for pins 9-16 to the chip on the other side (column 9).

There could be a broken trace still, separating column 9 from column 7. So check there is the same continuity between those chips, or check each pin of the replacement to the chips on both sides (not just the closer side).

Similarly, the traces that go to the chip "below" (pins 2 & 14), may not continue to the chip above, so check these pins connect to both the chip below and the chip above.

Hi, thanks for your help on this.  I thinking after tinkering with the RAM and looking at the diagrams I can see the following

the new chip should have connectivity on the following pins

LEFT CHIP                                  REPLACEMENT      RIGHT CHIP

9  (connected should be beep)     9            8      8 (connected should be beep for continuity)
10 (connected should be beep)    10          7      7 (connected should be beep for continuity)
11 (connected should be beep)    11          6      6 (connected should be beep for continuity)
12 (connected should be beep)    12          5      5 (connected should be beep for continuity)
13 (connected should be beep)    13          4      4 (connected should be beep for continuity)
14 (connected to TOP/BOTTOM)  14         3      3 (connected should be beep for continuity)
15 (connected should be beep)    15          2      2 (is connected to TOP and BOTTOM chip)
16 (connected should be beep)    16          1      1 (not connected, no beep for continuity)

here's the video
https://www.youtube.com/shorts/VKErDlzzJ_Q