After replacing all sockets (except for U9, U11,U10) and ALL connector pins on this MPU board, noticed I had no 1000's digit and no 10's in all displays. Found the issue to be I left 2 pins unsoldered at J1 on MPU board. Lightly soldered those in properly and now displays all work well but now erratic CPU noise upon bootup and during game. Replaced all 40 pin sockets as thought perhaps U11 or U9 bad sockets to blame for it co-incedently. No change after socket replacement (U9,U10,U11) and even swapped in new U11, U10 and U9 ICs.
Lastly unsoldered J1 pin strip as this is the last thing I did before encountering this sound issue, inspected for bridging etc (no issues found) soldered new J1 pin strip in again. Same issue.

Checked game with an Alltek installed and no sound issue. Proving problem resides on the -17 MPU.

Video showing problem here:

Problem now fixed. MPU J5 pin 14 and 15 were not connected to U9 pin 17 and 16 respectively. Repaired those breaks and viola! Success!

Sound like ET trying to phone home....

Thanks to you and my local buddy John who both said check your J5 pins and continuity again. Did that and found the issues! Thanks guys!!!

J5 is critical to be 100% continuity on each pin going to it's path on the MPU board for sound to be 100% in Stern SS games.

Problem now fixed. MPU J5 pin 14 and 15 were not connected to U9 pin 17 and 16 respectively. Repaired those breaks and viola! Success!