Here is my list of Alpha transformer AC voltages (AC unless DC is stated)

My guess would be model 86 or 89, Can you recheck the HVAC winding? -the manuals show more but who knows..

Both use two 3CX800s with 13.5V filaments.

The manuals are on

http://bama.edebris.com/manuals/alpha/ so you may look at the schematics and see what matches. Sometimes there are options or weights stated and pics of the transformer. A clue is that there is one 15 pin connector. These are a little weird because they have but one primary winding and most Alphas have two, and some a third interconnected buck/boost. Could it be a 240V winding? There are other models and the best I can do is guess.

77DX 77SX

2x 120, 1800/2800VAC, 5VAC, ?wt-rd, wt-gry. 8877 tube 5VAC

374

2x 120 /w tap, HVDC 2200/1400 (pri.tap), 25-40VDC, 2 or 3x 8874s fil 6.3VAC

374A

2x120, 5 or 25VAC unclear connected to one 120V winding, 1100/1750VAC, 40VCT, 2x8874 fil 6.3VAC

PA-76, 76P, 76C

2x120, 25VAC (buck?) connected to one 120V winding, 1100/1750VAC, 40VCT, 2 or 3x 8874 fil 6.3VAC, option R for hi/lo HV

76A, 76PA, 76CA

2x120, 25VAC (buck?) connected to one 120V winding, 1100/1750VAC, 40VCT, 2 or 3x 8874 fil 6.3VAC, option for hi/lo HV

78

2x120, (110-130VAC/220-250VAC) 25VAC (buck?) connected to one 120V winding, 1100/1750VAC, 40VCT, 2 or 3x 8874 fil 6.3VAC, option for hi/lo HV

86

2x 110V, 25V, 1250/1885VAC, 50VCT, 7VCT, 13.5V(FIL), 2x 3CX80089

200/220/240VAC, 1350/1900VAC, 7V, 51VCT, 13.6V(FIL), 2x 3CX800A791B

100/120V/200/220/240V, 2050V, 14V, 105V, 310V, 28VCT, 2x 4CX800/GU74B (12.6V fil)

PA-77

120/240V, 5V, 44VCT, HV 2400/3700VDC, one 8877 (6.3V fil)