The Tek 11801 has 4 Panasonic BR 2/3 A 1200 mAh 3 V lithium cells. All of those tested at 3.07 to 3.1 V despite manufacturing dates of 12-87 and 09-88. I think the fundamental issue with the NVRAM is the cells are too small. The ST battery caps for the SMD parts have a choice of 40 or 120 mAh capacities.
Once I get my replacements I'll try to reverse engineer the circuit in the NVRAM sockets.
