Just checking to be clear - you said "...only 3.37V AC across T7 and T9," which is somewhat ambiguous. You should get 6.6 volts with one probe on T7 and the other on T9. T8 is the centertap, which is grounded to safety ground (the chassis), so if one probe is grounded and the other is on T7 or on T9, you will get 3.3VAC.