Larry,
I e-mailed Larry Larsen @ NCE last week inquiring about sending my old SB3 in to be upgraded. He sent me the following response:
The upgrade path is to send the SB3 in to us at: NCE Warranty Center 82 East Main St. Webster, NY 14580 Include your name, address, phone number and payment of $59.95 which is the difference in the cost of the SB3 and the SB3a.
https://tstage9.wixsite.com/nyc-modeling
Time...It marches on...without ever turning around to see if anyone is even keeping in step.