The last tube will be 12AT6 or 12AV6 (Interchangeable). Your 128a6 will actually be 12BA6.
Norm
: can aney one help me with the tube layout for a zenith model B5O8R CHASSIS 5ZO5 missing one tube i have a 50c5 a 35w4 a 128a6 a 12be6 cant find out what the last one was. thanks seth